Revistas
Revista:
FRONTIERS IN PLANT SCIENCE
ISSN:
1664-462X
Año:
2023
Vol.:
14
Págs.:
1180688
Many studies have shown the capacity of soil humic substances (HS) to improve plant growth in natural ecosystems. This effect involves the activation of different processes within the plant at different coordinated molecular, biochemical, and physiological levels. However, the first event triggered by plant root-HS interaction remains unclear. Some studies suggest the hypothesis that the interaction of HS with root exudates involves relevant modification of the molecular conformation of humic self-assembled aggregates, including disaggregation, which might be directly involved in the activation of root responses. To investigate this hypothesis, we have prepared two humic acids. A natural humic acid (HA) and a transformed humic acid obtained from the treatment of HA with fungal laccase (HA enz). We have tested the capacity of the two humic acids to affect plant growth (cucumber and Arabidopsis) and complex Cu. Laccase-treatment did not change the molecular size but increased hydrophobicity, molecular compactness and stability, and rigidity of HA enz. Laccase-treatment avoided the ability of HA to promote shoot- and root-growth in cucumber and Arabidopsis. However, it does not modify Cu complexation features. There is no molecular disaggregation upon the interaction of HA and HA enz with plant roots. The results indicate that the interaction with plant roots induced in both HA and laccase-treated HA (HA enz), changes in their structural features that showed higher compactness and rigidity. These events might result from the interaction of HA and HA enz with specific root exudates that can promote intermolecular crosslinking. In summary, the results indicate that the weakly bond stabilized aggregated conformation (supramolecular-like) of HA plays a crucial role in its ability to promote root and shoot growth. The results also indicate the presence of two main types of HS in the rhizosphere corresponding to those non-interacting with plant roots (forming aggregated molecular assemblies) and those produced after interacting with plant root exudates (forming stable macromolecules).
Autores:
Santana, M. M. (Autor de correspondencia); Rosa, A. P.; Zamarreño, Ángel; et al.
Revista:
AGRONOMY
ISSN:
2073-4395
Año:
2022
Vol.:
12
N°:
4
Págs.:
934
The effect of seed coating salt-stressed tomato with the bacterium Achromobacter xylosoxidans BOA4 and/or irrigation with an extract of the marine algae Enteromorpha intestinalis (EI) is herein evaluated. The plant shoots and roots were harvested separately on day 50, following extensive saline stress. The addition of BOA4 and/or EI extract resulted in an average increase of 33% in plant shoot DW, but an averaged decrease of 44% in the root to shoot biomass ratio. Anthocyanin content increased by over 34% and 44% with EI and BOA4 plus EI treatments, respectively. Since enhanced protein tyrosine nitration (PTN) is a known plant response to salt stress, the PTN level was inspected through 3-nitrotyrosine content determination. This was drastically increased by salt stress; however, BOA4, EI or both caused an averaged PTN decrease of 30% in stressed roots or shoots. This PTN response could be associated with tomato phenotypic characteristics and is postulated to be inversely correlated to cytokinin contents in stressed plants, namely cis-zeatin-type-cis-zeatin (cZ) plus cis-zeatin riboside (cZR), and isopentenyladenine (iP). The latter showed a drastic average increase by 3.6-fold following BOA4 and/or EI treatments of salinized tomato. This increment could be related to cytokinin biosynthesis induced by the applied bio-stimulants; IP and derivatives are the main cytokinins in seaweeds, and Achromobacter xylosoxidans BOA4 was shown to produce up to 17.5 pmol mL -1 of isopentenyladenine. This work is the first report on the influence of bio-stimulants, used to improve salt stress tolerance, on plant PTN levels; BOA4 and/or EI treatments decreased PTN, while increasing cis-zeatin-type and iP cytokinins in tomato, the latter showed an enhanced tolerance to salt stress.
Autores:
Soriano, G.; Kneeshaw, S.; Jiménez-Alemán, G.; et al.
Revista:
NEW PHYTOLOGIST
ISSN:
0028-646X
Año:
2022
Vol.:
233
N°:
3
Págs.:
1401 - 1413
Jasmonates are fatty acid-derived hormones that regulate multiple aspects of plant development, growth and stress responses. Bioactive jasmonates, defined as the ligands of the conserved COI1 receptor, differ between vascular plants and bryophytes (jasmonoyl-l-isoleucine (JA-Ile) and dinor-12-oxo-10,15(Z)-phytodienoic acid (dn-OPDA), respectively). The biosynthetic pathways of JA-Ile in the model vascular plant Arabidopsis thaliana have been elucidated. However, the details of dn-OPDA biosynthesis in bryophytes are still unclear. Here, we identify an orthologue of Arabidopsis fatty-acid-desaturase 5 (AtFAD5) in the model liverwort Marchantia polymorpha and show that FAD5 function is ancient and conserved between species separated by more than 450 million years (Myr) of independent evolution. Similar to AtFAD5, MpFAD5 is required for the synthesis of 7Z-hexadecenoic acid. Consequently, in Mpfad5 mutants, the hexadecanoid pathway is blocked, dn-OPDA concentrations are almost completely depleted and normal chloroplast development is impaired. Our results demonstrate that the main source of wounding-induced dn-OPDA in Marchantia is the hexadecanoid pathway and the contribution of the octadecanoid pathway (i.e. from OPDA) is minimal. Remarkably, despite extremely low concentrations of dn-OPDA, MpCOI1-mediated responses to wounding and insect feeding can still be activated in Mpfad5, suggesting that dn-OPDA may not be the only bioactive jasmonate and COI1 ligand in Marchantia.
Revista:
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
ISSN:
1422-0067
Año:
2022
Vol.:
23
N°:
17
Págs.:
9976
Currently, high doses of vinasse are employed for the fertigation of sugarcane with positive results on yield. Usually, this effect is related to the presence of mineral nutrients in its composition as well as to its action on soil properties. Consequently, the concentrations of minerals, organic acids, and other metabolites in vinasse are very well characterized. However, considering that cane vinasses are obtained from the treatment of vegetal tissues, it is also possible that they might contain significant concentrations of phytoregulators that could have a relevant role in their beneficial action on yield. To investigate this hypothesis, we analyzed the main plant hormones in 22 samples of vinasse collected in different production sites of Brazil using HPLC-mass spectrometry. The results show that both ABA and IAA present concentrations in vinasse within the micromolar range, thus being potential active ingredients affecting plant development. In conclusion, the beneficial action of cane vinasses on sugarcane yield might involve, among other factors, the action of IAA and ABA on plant growth.
Revista:
FRONTIERS IN PLANT SCIENCE
ISSN:
1664-462X
Año:
2022
Vol.:
13
Págs.:
803013
Many studies have shown the close relationship between the beneficial action of soil and sedimentary humic acids on the growth of plants cultivated in calcareous soils and their ability to improve Fe plant nutrition. These results have been ascribed to the humic acid (HA) capability to improve Fe solubility and bioavailability. However, other effects more related to a humic acid action on the specific mechanisms activated in roots of plants under Fe deficiency cannot be ruled out. Although this question has been studied in dicotyledonous plants, in graminaceous plants there are no specific studies. Here we investigate the ability of a humic acid extracted from peat (HA) to improve Fe nutrition in wheat plants cultivated under Fe deficient and sufficient conditions. The results show that HA can improve the physiological status of Fe deficient wheat plants by alleviating some of the deleterious consequences of Fe deficiency on plant development and increasing the plant ability to secrete phytosiderophores to the nutrient solution. This action of HA is associated with increases in the Fe-active pool in leaves that might be related to the mobilization of the Fe complexed by HA resulting from the interaction of HA with the phytosiderophores in the nutrient solution. The Fe translocation from the root to the shoot may be favored by the action of trans-Zeatin Riboside (tZR) since the leaf concentration of this phytohormone was enhanced by HA in Fe deficient plants.
Autores:
Monte, I. (Autor de correspondencia); Caballero, J.; Zamarreño, Ángel; et al.
Revista:
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
ISSN:
0027-8424
Año:
2022
Vol.:
119
N°:
49
Págs.:
e2212155119
Jasmonates are phytohormones that regulate defense and developmental processes in land plants. Despite the chemical diversity of jasmonate ligands in different plant lineages, they are all perceived by COI1/JAZ co-receptor complexes, in which the hormone acts as a molecular glue between the COI1 F-box and a JAZ repressor. It has been shown that COI1 determines ligand specificity based on the receptor crystal structure and the identification of a single COI1 residue, which is responsible for the evolutionary switch in ligand binding. In this work, we show that JAZ proteins contribute to ligand specificity together with COI1. We propose that specific features of JAZ proteins, which are conserved in bryophytes and lycophytes, enable perception of dn-OPDA ligands regardless the size of the COI1 binding pocket. In vascular plant lineages beyond lycophytes, JAZ evolved to limit binding to JA-Ile, thus impeding dn-OPDA recognition by COI1.
Autores:
Kneeshaw, S.; Soriano, G.; Monte, I.; et al.
Revista:
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
ISSN:
0027-8424
Año:
2022
Vol.:
119
N°:
36
Págs.:
e2202930119
In plants, jasmonate signaling regulates a wide range of processes from growth and development to defense responses and thermotolerance. Jasmonates, such as jasmonic acid (JA), (+)-7-iso-jasmonoyl-L-isoleucine (JA-Ile), 12-oxo-10,15(Z)-phytodienoic acid (OPDA), and dinor-12-oxo-10,15(Z)-phytodienoic acid (dn-OPDA), are derived from C18 (18 Carbon atoms) and C16 polyunsaturated fatty acids (PUFAs), which are found ubiquitously in the plant kingdom. Bryophytes are also rich in C20 and C22 long-chain polyunsaturated fatty acids (LCPUFAs), which are found only at low levels in some vascular plants but are abundant in organisms of other kingdoms, including animals. The existence of bioactive jasmonates derived from LCPUFAs is currently unknown. Here, we describe the identification of an OPDA-like molecule derived from a C20 fatty acid (FA) in the liverwort Marchantia polymorpha (Mp), which we term (5Z,8Z)-10-(4-oxo-5-((Z)-pent-2-en-1-yl)cyclopent-2-en-1-yl)deca-5,8-dienoic acid (C20-OPDA). This molecule accumulates upon wounding and, when applied exogenously, can activate known Coronatine Insensitive 1 (COI1) -dependent and -independent jasmonate responses. Furthermore, we identify a dn-OPDA-like molecule (Delta(4)-dn-OPDA) deriving from C20-OPDA and demonstrate it to be a ligand of the jasmonate coreceptor (MpCOI1-Mp Jasmonate-Zinc finger inflorescence meristem domain [MpJAZ]) in Marchantia. By analyzing mutants impaired in the production of LCPUFAs, we elucidate the major biosynthetic pathway of C20-OPDA and Delta(4)-dn-OPDA. Moreover, using a double mutant compromised in the production of both Delta(4)-dn-OPDA and dn-OPDA, we demonstrate the additive nature of these molecules in the activation of jasmonate responses. Taken together, our data identify a ligand of MpCOI1 and demonstrate LCPUFAs as a source of bioactive jasmonates that are essential to the immune response of M. polymorpha.
Autores:
Nardi, S.; Schiavon, M. (Autor de correspondencia); Muscolo, A.; et al.
Revista:
FRONTIERS IN PLANT SCIENCE
ISSN:
1664-462X
Año:
2022
Vol.:
13
Págs.:
851451
Autores:
Nicolás, M. (Autor de correspondencia); Torres-Pérez, R.; Wahl, V.; et al.
Revista:
NATURE PLANTS
ISSN:
2055-026X
Año:
2022
Vol.:
8
N°:
3
Págs.:
281 - 294
In potato, the TCP transcription factor BRANCHED1b represses aerial tuber formation in the axils of the leaves. It functions through limiting the number of plasmodesmata, reducing sucrose levels and repressing the tuberigen protein SP6A.
The control of carbon allocation, storage and usage is critical for plant growth and development and is exploited for both crop food production and CO2 capture. Potato tubers are natural carbon reserves in the form of starch that have evolved to allow propagation and survival over winter. They form from stolons, below ground, where they are protected from adverse environmental conditions and animal foraging. We show that BRANCHED1b (BRC1b) acts as a tuberization repressor in aerial axillary buds, which prevents buds from competing in sink strength with stolons. BRC1b loss of function leads to ectopic production of aerial tubers and reduced underground tuberization. In aerial axillary buds, BRC1b promotes dormancy, abscisic acid responses and a reduced number of plasmodesmata. This limits sucrose accumulation and access of the tuberigen protein SP6A. BRC1b also directly interacts with SP6A and blocks its tuber-inducing activity in aerial nodes. Altogether, these actions help promote tuberization underground.
Autores:
Ruiz-Lozano, J. M. (Autor de correspondencia); Quiroga, G.; Erice, G.; et al.
Revista:
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
ISSN:
1422-0067
Año:
2022
Vol.:
23
N°:
17
Págs.:
9822
In this study, a first experiment was conducted with the objective of determining how drought stress alters the radial water flow and physiology in the whole maize nested association mapping (NAM) population and to find out which contrasting maize lines should be tested in a second experiment for their responses to drought in combination with an arbuscular mycorrhizal (AM) fungus. Emphasis was placed on determining the role of plant aquaporins and phytohormones in the responses of these contrasting maize lines to cope with drought stress. Results showed that both plant aquaporins and hormones are altered by the AM symbiosis and are highly involved in the physiological responses of maize plants to drought stress. The regulation by the AM symbiosis of aquaporins involved in water transport across cell membranes alters radial water transport in host plants. Hormones such as IAA, SA, ABA and jasmonates must be involved in this process either by regulating the own plant-AM fungus interaction and the activity of aquaporins, or by inducing posttranscriptional changes in these aquaporins, which in turns alter their water transport capacity. An intricate relationship between root hydraulic conductivity, aquaporins and phytohormones has been observed, revealing a complex network controlling water transport in maize roots.
Autores:
Navarro, C.; Mateo-Elizalde, C.; Mohan, T. C.; et al.
Revista:
MOLECULAR PLANT
ISSN:
1674-2052
Año:
2021
Vol.:
14
N°:
9
Págs.:
1489 - 1507
In nature, plants acquire nutrients from soils to sustain growth, and at the same time, they need to avoid the uptake of toxic compounds and/or possess tolerance systems to cope with them. This is particularly challenging when the toxic compound and the nutrient are chemically similar, as in the case of phosphate and arsenate. In this study, we demonstrated that regulatory elements of the phosphate starvation response (PSR) coordinate the arsenate detoxification machinery in the cell. We showed that arsenate repression of the phosphate transporter PHT1;1 is associated with the degradation of the PSR master regulator PHR1. Once arsenic is sequestered into the vacuole, PHR1 stability is restored and PHT1;1 expression is recovered. Furthermore, we identified an arsenite responsive SKP1-like protein and a PHR1 interactor F-box (PHIF1) as constituents of the SCF complex responsible for PHR1 degradation.We found that arsenite, the form to which arsenate is reduced for compartmentalization in vacuoles, represses PHT1;1 expression, providing a highly selective signal versus phosphate to control PHT1;1 expression in response to arsenate. Collectively, our results provide molecular insights into a sensing mechanism that regulates arsenate/phosphate uptake depending on the plant's detoxification capacity.
Autores:
Santos-Reis de Andrade da Silva, M.; Huertas-Tavares, O. C.; Gonçalves-Ribeiro, T.; et al.
Revista:
APPLIED SOIL ECOLOGY
ISSN:
0929-1393
Año:
2021
Vol.:
168
Págs.:
104146
Humic acids (HA) stimulate the growth of several plant species by regulating their hormonal and redox metabolisms. Nevertheless, studies on their relationship with the plant-associated microbiota are almost nonexistent. Here, we hypothesized that the HA effect occurs in parallel with the regulation of the plant-associated bacterial community. Rice was grown for 264 h in nutrient solution supplied or not with HA (80 mg L-1). Plant growth was evaluated every 24 h and samples for 16S rRNA gene sequencing were taken after 240 h. The plant's net assimilation rate and the absolute and relative growth rates increased from 100 h to 264 h after the first HA application. The root volume and other growth variables were stimulated at different times along the plant growth cycle. Metataxonomics revealed that bacterial community structure and composition were affected upon HA application. The interactions between members of the community increased in HA-treated roots, showing more connected bacterial communities. Chitinophaga and Mucilaginibacter were the predominant genera in HA treated roots. These bacteria are reported to produce enzymes that degrade compounds present in the wall of fungi, oomycetes , and nematode eggs. Pseudomonas and Acidobacteria Gp 1, both siderophore-producers and plant-growth promoters were also enriched, although with lower abundances.
Revista:
ENVIRONMENTAL RESEARCH
ISSN:
0013-9351
Año:
2021
Vol.:
194
Págs.:
110726
Revista:
HORTICULTURA
ISSN:
2340-2903
Año:
2021
Vol.:
1
N°:
352
Págs.:
40 - 43
Revista:
MOLECULES
ISSN:
1420-3049
Año:
2021
Vol.:
26
N°:
1
Págs.:
3
Some studies have reported that the capacity of humic substances to improve plant growth is dependent on their ability to increase root hydraulic conductivity. It was proposed that this effect is directly related to the structural conformation in solution of these substances. To study this hypothesis, the effects on root hydraulic conductivity and growth of cucumber plants of a sedimentary humic acid and two polymers-polyacrylic acid and polyethylene glycol-presenting a molecular conformation in water solution different from that of the humic acid have been studied. The results show that whereas the humic acid caused an increase in root hydraulic conductivity and plant growth, both the polyacrylic acid and the polyethylene glycol did not modify plant growth and caused a decrease in root hydraulic conductivity. These results can be explained by the different molecular conformation in water solution of the three molecular systems. The relationships between these biological effects and the molecular conformation of the three molecular systems in water solution are discussed.
Autores:
Conesa, C. M.; Saez, A.; Navarro-Neila, S.; et al.
Revista:
PLANTS
ISSN:
2223-7747
Año:
2020
Vol.:
9
N°:
2
Págs.:
251
Nitrogen (N) is probably the most important macronutrient and its scarcity limits plant growth, development and fitness. N starvation response has been largely studied by transcriptomic analyses, but little is known about the role of alternative polyadenylation (APA) in such response. In this work, we show that N starvation modifies poly(A) usage in a large number of transcripts, some of them mediated by FIP1, a component of the polyadenylation machinery. Interestingly, the number of mRNAs isoforms with poly(A) tags located in protein-coding regions or 5 '-UTRs significantly increases in response to N starvation. The set of genes affected by APA in response to N deficiency is enriched in N-metabolism, oxidation-reduction processes, response to stresses, and hormone responses, among others. A hormone profile analysis shows that the levels of salicylic acid (SA), a phytohormone that reduces nitrate accumulation and root growth, increase significantly upon N starvation. Meta-analyses of APA-affected and fip1-2-deregulated genes indicate a connection between the nitrogen starvation response and salicylic acid (SA) signaling. Genetic analyses show that SA may be important for preventing the overgrowth of the root system in low N environments. This work provides new insights on how plants interconnect different pathways, such as defense-related hormonal signaling and the regulation of genomic information by APA, to fine-tune the response to low N availability.
Autores:
Monte, I.; Kneeshaw, S.; Franco-Zorrilla, J. M.; et al.
Revista:
CURRENT BIOLOGY
ISSN:
0960-9822
Año:
2020
Vol.:
30
N°:
6
Págs.:
962 - 971
The jasmonate signaling pathway regulates development, growth, and defense responses in plants. Studies in the model eudicot, Arabidopsis thaliana, have identified the bioactive hormone (jasmonoylisoleucine [JA-Ile]) and its Coronatine Insensitive 1 (COI1)/Jasmonate-ZIM Domain (JAZ) co-receptor. In bryophytes, a conserved signaling pathway regulates similar responses but uses a different ligand, the JA-Ile precursor dinor-12-oxo-10,15(Z)-phytodienoic acid (dn-OPDA), to activate a conserved co-receptor. Jasmonate responses independent of JA-Ile and COI1, thought to be mediated by the cyclopentenone OPDA, have also been suggested, but experimental limitations in Arabidopsis have hindered attempts to uncouple OPDA and JA-Ile biosynthesis. Thus, a clear understanding of this pathway remains elusive. Here, we address the role of cyclopentenones in COI1-independent responses using the bryophyte Marchantia polymorpha, which is unable to synthesize JA-Ile but does accumulate OPDA and dn-OPDA. We demonstrate that OPDA and dn-OPDA activate a COI1-independent pathway that regulates plant thermotolerance genes, and consequently, treatment with these oxylipins protects plants against heat stress. Furthermore, we identify that these molecules signal through their electrophilic properties.
Revista:
AGRONOMY JOURNAL
ISSN:
0002-1962
Año:
2020
Vol.:
10
N°:
7
Págs.:
968
Because of the low consistency of the results obtained in the field, the use of biochar as a soil amendment is controversial. Thus, in general, in acidic soils, results are positive, while in alkaline soils, they are non-significant or even negative. The results regarding biochar action in acidic soils have been related to a lime-like effect due to its alkaline pH and the high doses normally used. However, the causes of biochar effects in alkaline soils remain unknown. Our objective was to explore the chemical mechanism of biochar interaction in acidic and alkaline soils. We used well-characterized biochar as a component of two complex N and PK granulated fertilizers at two different doses (1% and 5%). These fertilizers were applied to wheat cultivated in pots containing an alkaline soil and grown for 60 days. No effect was shown for the N-biochar fertilizer application. However, the PK-biochar fertilizer application caused a decrease in crop yield. In addition, the adsorption isotherms of Al, Fe, Mo, Mn, and Phosphate (Pi) in biochar were also studied. The results showed that Fe and Al were rapidly adsorbed in biochar, while Pi was only adsorbed on the Fe-, Al-biochar complex. Desorption experiments showed that P and Fe/Al were not desorbed from the P-Fe/Al-biochar complex by water or the Olsen reagent, while partial desorption was observed when HCl 0.1 M was used.
Autores:
Chico, J. M.; Lechner, E.; Fernandez-Barbero, G.; et al.
Revista:
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
ISSN:
0027-8424
Año:
2020
Vol.:
117
N°:
11
Págs.:
6205 - 6215
The jasmonate (JA)-pathway regulators MYC2, MYC3, and MYC4 are central nodes in plant signaling networks integrating environmental and developmental signals to fine-tune JA defenses and plant growth. Continuous activation of MYC activity is potentially lethal. Hence, MYCs need to be tightly regulated in order to optimize plant fitness. Among the increasing number of mechanisms regulating MYC activity, protein stability is arising as a major player. However, how the levels of MYC proteins are modulated is still poorly understood. Here, we report that MYC2, MYC3, and MYC4 are targets of BPM (BTB/POZ-MATH) proteins, which act as substrate adaptors of CUL3-based E3 ubiquitin ligases. Reduction of function of CUL3(BPM) in amiR-bpm lines, bpm235 triple mutants, and cul3ab double mutants enhances MYC2 and MYC3 stability and accumulation and potentiates plant responses to JA such as root-growth inhibition and MYC-regulated gene expression. Moreover, MYC3 polyubiquitination levels are reduced in amiR-bpm lines. BPM3 protein is stabilized by JA, suggesting a negative feedback regulatory mechanism to control MYC activity, avoiding harmful runaway responses. Our results uncover a layer for JA-pathway regulation by CUL3(BPM)-mediated degradation of MYC transcription factors.
Revista:
FRONTIERS IN PLANT SCIENCE
ISSN:
1664-462X
Año:
2020
Vol.:
11
Págs.:
837
The global decrease in soil fertility leads to a new agricultural scenario where eco-friendly solutions play an important role. The plant growth promotion through the use of microbes, especially endophytes and rhizosphere microbiota, has been proposed as a useful solution. Several studies have shown that humic substances are suitable vehicles for the inoculation of plant growth promoting bacteria, and that this combination has an enhanced effect on the stimulation of plant development. In this work, cucumber plants grown hydroponically have been pre-treated with a sedimentary humic acid (SHA) with known plant growth-enhancing effects, and culturable bacterial endophytes have been isolated from these plants. The hypothesis was that this pre-treatment with SHA could lead to the isolation of certain endophytic taxa whose proliferation within the plant could have been promoted as a result of the effects of the treatment with SHA, and that could eventually reinforce a potential synergistic effect of a combined application of those endophytic bacteria and SHA. The culturable endophytes that have been isolated from humic acid-treated cucumber plants have been identified as members of four main phyla:Proteobacteria,Firmicutes,Actinobacteria, andBacteroidetes. Isolates were characterized according to the following plant growth-promoting traits: nitrogen fixation/scavenging, phosphate solubilization, siderophore production and plant hormone production. Most of the isolates were able to fix/scavenge nitrogen and to produce plant hormones (indole-3-acetic acid and several cytokinins), whereas few isolates were able to solubilize phosphate and/or produce siderophores. The most promising endophyte isolates for its use in futures investigations as plant growth-promoting bacterial inocula werePseudomonassp. strains (that showed all traits),Sphingomonassp.,Stenotrophomonassp. strains, or someArthrobactersp. andMicrobacteriumsp. isolates.
Revista:
FRONTIERS IN PLANT SCIENCE
ISSN:
1664-462X
Año:
2020
Vol.:
11
Págs.:
493
Humic substances (HS, fulvic and humic acids) are widely used as fertilizers or plant growth stimulants, although their mechanism of action still remains partially unknown. Humic substances may be applied either directly to the soil or as foliar sprays. Despite both kind of application are commonly used in agricultural practices, most of the studies regarding the elicited response in plants induced by HS are based on the root-application of these substances. The present work aimed at discriminating between the mechanisms of action of foliar application versus root application of a sedimentary humic acid (SHA) on plant development. For this purpose, six markers related to plant phenotype, plant morphology, hormonal balance and root-plasma membrane H+-ATPase were selected. Both application strategies improved the shoot and root growth. Foliar applied- and root applied-SHA shared the capacity to increase the concentration of indole-3-acetic acid in roots and cytokinins in shoots. However, foliar application did not lead to short-term increases in either abscisic acid root-concentration or root-plasma membrane H+-ATPase activity which are, however, two crucial effects triggered by SHA root-application. Both application modes increased the root concentrations of jasmonic acid and jasmonoyl-isoleucine. These hormonal changes caused by foliar application could be a stress-related symptom and connected to the loss of leaves trichomes and the diminution of chloroplasts size seen by scanning electron microscopy. These results support the hypothesis that the beneficial effects of SHA applied to roots or leaves may result from plant adaptation to a mild transient stress caused by SHA application.
Autores:
Tcherkez, G.; Mariem, S.B.; Larraya, L.; et al.
Revista:
JOURNAL OF EXPERIMENTAL BOTANY
ISSN:
0022-0957
Año:
2020
Vol.:
71
N°:
19
Págs.:
5990 - 6003
While the general effect of CO2 enrichment on photosynthesis, stomatal conductance, N content, and yield has been documented, there is still some uncertainty as to whether there are interactive effects between CO2 enrichment and other factors, such as temperature, geographical location, water availability, and cultivar. In addition, the metabolic coordination between leaves and grains, which is crucial for crop responsiveness to elevated CO2, has never been examined closely. Here, we address these two aspects by multi-level analyses of data from several free-air CO2 enrichment experiments conducted in five different countries. There was little effect of elevated CO2 on yield (except in the USA), likely due to photosynthetic capacity acclimation, as reflected by protein profiles. In addition, there was a significant decrease in leaf amino acids (threonine) and macroelements (e.g. K) at elevated CO2, while other elements, such as Mg or S, increased. Despite the non-significant effect of CO2 enrichment on yield, grains appeared to be significantly depleted in N (as expected), but also in threonine, the S-containing amino acid methionine, and Mg. Overall, our results suggest a strong detrimental effect of CO2 enrichment on nutrient availability and remobilization from leaves to grains.
Revista:
ENVIRONMENTAL RESEARCH
ISSN:
0013-9351
Humification is a process that plant and microbiota residues experiment in natural or agronomic soils under microorganisms action and environmental conditions. Under this process natural biomolecules - such as protein, carbohydrates or lignin - experience secondary biochemical and chemical reactions yielding to the formation of new organic biomolecules normally known as soil humus or humic substances (HS). In parallel, composting of fresh organic residues may be seen as an artificial process that involves many microorganism-induced secondary biochemical reactions that are probably also included in the first steps of natural humification in soils.
In this context, we have applied multivariate statistical analysis to diverse and complementary analytical techniques (UV-Visible, synchronous fluorescence, FTIR, C-13-NMR and pyrolysis GS/MS) to follow the structural evolution of three groups of organic material: (i) fresh organic matter materials, (ii) compost of the fresh organic matter materials, and (iii) humic and fulvic acids including standards and references from the International Humic Substances Society. In order to discriminate among the three groups of organic materials, the set of data obtained from each analytical technique was analyzed using complementary statistical techniques: Correlations, Kolmogorov-Smirnov Test and Principal Component Analysis (PCA).
The results showed positive correlations between UV-visible and fluorescence indexes and aromatic structures ...
Revista:
JOURNAL OF PLANT PHYSIOLOGY
ISSN:
0176-1617
Año:
2020
Vol.:
246 - 247
N°:
153115
Págs.:
153115
Drought stress is one of the most devastating abiotic stresses, compromising crop growth, reproductive success and yield. The arbuscular mycorrhizal (AM) symbiosis has been demonstrated to be beneficial in helping the plant to bear with water deficit. In plants, development and stress responses are largely regulated by a complex hormonal crosstalk. Auxins play significant roles in plant growth and development, in responses to different abiotic stresses or in the establishment and functioning of the AM symbiosis. Despite these important functions, the role of indole-3acetic acid (IAA) as a regulator of root water transport and stress response is not well understood. In this study, the effect of exogenous application of IAA on the regulation of root radial water transport in AM plants was analyzed under well-watered and drought stress conditions. Exogenous IAA application affected root hydraulic parameters, mainly osmotic root hydraulic conductivity (Lo), which was decreased in both AM and non-AM plants under water deficit conditions. Under drought, the relative apoplastic water flow was differentially regulated by IAA application in non-AM and AM plants. The effect of IAA on the internal cell component of root water conductivity suggests that aquaporins are involved in the IAA-dependent inhibition of this water pathway.
Autores:
Hernández-Apaolaza, L. (Autor de correspondencia); Escribano, L.; Zamarreño, Ángel; et al.
Revista:
FRONTIERS IN PLANT SCIENCE
ISSN:
1664-462X
Año:
2020
Vol.:
11
Págs.:
580552
Silicon has not been cataloged as an essential element for higher plants. However, it has shown beneficial effects on many crops, especially under abiotic and biotic stresses. Silicon fertilization was evaluated for the first time on plants exposed to fluctuations in an Fe regime (Fe sufficiency followed by Fe deficiency and, in turn, by Fe resupply). Root and foliar Si applications were compared using cucumber plants that were hydroponically grown in a growth chamber under different Fe nutritional statuses and Si applied either to the roots or to the shoots. The SPAD index, Fe, and Mn concentration, ROS, total phenolic compounds, MDA concentration, phytohormone balance, and cell cycle were determined. The results obtained showed that the addition of Si to the roots induced an Fe shortage in plants grown under optimal or deficient Fe nutritional conditions, but this was not observed when Si was applied to the leaves. Plant recovery following Fe resupply was more effective in the Si-treated plants than in the untreated plants. A relationship between the ROS concentration, hormonal balance, and cell cycle under different Fe regimes and in the presence or absence of Si was also studied. The contribution of Si to this signaling pathway appears to be related more to the induction of Fe deficiency, than to any direct biochemical or metabolic processes. However, these roles could not be completely ruled out because several hormone differences could only be explained by the addition
Autores:
I.; Franco-Zorrilla, J. M.; G.; et al.
Revista:
MOLECULAR PLANT
ISSN:
1674-2052
Año:
2019
Vol.:
12
N°:
2
Págs.:
185 - 198
JAZ proteins are negative regulators of jasmonate responses, acting both as repressors of transcription factors and as co-receptors of JA-Ile. The high redundancy of JAZ genes in angiosperms has hindered the characterization of a complete depletion of JAZ function. Moreover, the recent discovery that dn-OPDA is the jasmonate ligand in Marchantia polymorpha demonstrates that JA-Ile is not the sole COI1/JAZ ligand in land plants and highlights the importance of studying JAZ co-receptors in bryophytes. Here, we have exploited the low gene redundancy of the liverwort M. polymorpha to characterize the single MpJAZ in this early diverging plant lineage. We clarify the phylogenetic history of the TIFY family, demonstrate that MpJAZ is the ortholog of AtJAZ with a conserved function, and characterize its repressor activity of dn-OPDA responses. Our results show that, consistent with previous findings in Arabidopsis, MpJAZ represses jasmonates biosynthesis, senescence, and plant defenses, and promotes cell growth and reproductive fitness, highlighting the power of studies in Marchantia.
Revista:
CURRENT BIOLOGY
ISSN:
0960-9822
Año:
2019
Vol.:
29
N°:
14
Págs.:
2270 - 2281
Evolutionary molecular plant-microbe interactions (EvoMPMI) is an emerging field bridging the gap between molecular phytopathology and evolutionary studies. EvoMPMI research is currently challenging due to the scarcity of pathogenic model systems in early-diverging land plants. Liverworts are among the earliest diverging land-plant lineages, and Marchantia polymorpha has emerged as a liverwort model for evolutionary studies. However, bacterial pathogens of Marchantia have not yet been discovered, and the molecular mechanisms controlling plant-pathogen interactions in this early-diverging land plant remain unknown. Here, we describe a robust experimental plant-bacterial pathosystem for EvoMPMI studies and discover that an ancient immune system governs plant-microbe interactions between M. polymorpha and the hemi-biotrophic pathogenic bacteria Pseudomonas syringae. We show that P. syringae pv tomato (Pto) DC3000, causal agent of tomato bacterial speck disease, colonizes M. polymorpha and activates typical hallmarks of plant innate immunity. Virulence of Pto DC3000 on M. polymorpha relies on effector activities inside liverwort cells, including conserved AvrPto and AvrPtoB functions. Host specificity analyses uncovered pathogenic differences among P. syringae strains, suggesting that M. polymorpha-P. syringae interactions are controlled by the genetic backgrounds of both host and pathogen.
Autores:
Garcia-Leon, M.; Cuyas, L.; Abd El-Moneim, D. ; et al.
Revista:
PLANT CELL
ISSN:
1040-4651
Año:
2019
Vol.:
31
N°:
10
Págs.:
2411 - 2429
The plant endosomal trafficking pathway controls the abundance of membrane-associated soluble proteins, as shown for abscisic acid (ABA) receptors of the PYRABACTIN RESISTANCE1/PYR1-LIKE/REGULATORY COMPONENTS OF ABA RECEPTORS (PYR/PYL/RCAR) family. ABA receptor targeting for vacuolar degradation occurs through the late endosome route and depends on FYVE DOMAIN PROTEIN REQUIRED FOR ENDOSOMAL SORTING1 (FYVE1) and VACUOLAR PROTEIN SORTING23A (VPS23A), components of the ENDOSOMAL SORTING COMPLEX REQUIRED FOR TRANSPORT-I (ESCRT-I) complexes. FYVE1 and VPS23A interact with ALG-2 INTERACTING PROTEIN-X (ALIX), an ESCRT-III-associated protein, although the functional relevance of such interactions and their consequences in cargo sorting are unknown. In this study we show that Arabidopsis (Arabidopsis thaliana) ALIX directly binds to ABA receptors in late endosomes, promoting their degradation. Impaired ALIX function leads to altered endosomal localization and increased accumulation of ABA receptors. In line with this activity, partial loss-of-function alix-1 mutants display ABA hypersensitivity during growth and stomatal closure, unveiling a role for the ESCRT machinery in the control of water loss through stomata. ABA-hypersensitive responses are suppressed in alix-1 plants impaired in PYR/PYL/RCAR activity, in accordance with ALIX affecting ABA responses primarily by controlling ABA receptor stability. ALIX-1 mutant protein displays reduced interaction with VPS23A and ABA receptors, providing a molecular basis for ABA hypersensitivity in alix-1 mutants. Our findings unveil a negative feedback mechanism triggered by ABA that acts via ALIX to control the accumulation of specific PYR/PYL/RCAR receptors.
Revista:
RSC ADVANCES
ISSN:
2046-2069
Año:
2019
Vol.:
9
N°:
44
Págs.:
25790 - 25796
Phosphate-metal-humic complexes are very relevant in nature due to their crucial role in phosphate availability for plants and microorganisms. Synthetic phosphate-calcium-humic acid (HA) complexes have proven to be efficient sources of available phosphorus for crops. However, the current knowledge about their structure and molecular features is very poor. The structural implications of phosphate interaction with humic binding sites through calcium bridges, in both monocalcium phosphate and dicalcium phosphate is investigated by using molecular modeling, P-31-NMR, H-1-NMR and X-ray diffractometry. The conformational changes in the molecular configuration of the humic acid involved in the interaction resulting from the synthetic process is also studied by using HPSEC and synchronous fluorescence. The results obtained allow us to identify the phosphate type in the crystalline phase that is involved in the interaction of humic acid binding sites and the different forms of calcium phosphate. Synchronous fluorescence also shows that whereas the conformational configuration of the HA binding site is only partially affected in the monocalcium phosphate interaction, it changes in the case of dicalcium phosphate showing simpler molecular arrangements. These changes in the molecular conformation of the binding site in HA in solution may influence the biological activity of the humic acid.
Revista:
PLANTS
ISSN:
2223-7747
Año:
2019
Vol.:
8
N°:
6
Págs.:
173
The total area under quinoa (Chenopodium quinoa Willd.) cultivation and the consumption of its grain have increased in recent years because of its nutritional properties and ability to grow under adverse conditions, such as drought. Climate change scenarios predict extended periods of drought and this has emphasized the need for new crops that are tolerant to these conditions. The main goal of this work was to evaluate crop yield and quality parameters and to characterize the physiology of two varieties of quinoa grown under water deficit in greenhouse conditions. Two varieties of quinoa from the Chilean coast (Rainbow) and altiplano (Illpa) were used, grown under full irrigation or two different levels of water deficit applied during the grain filling period. There were no marked differences in yield and quality parameters between treatments, but the root biomass was higher in plants grown under severe water deficit conditions compared to control. Photosynthesis, transpiration and stomatal conductance decreased with increased water stress in both cultivars, but the coastal variety showed higher water use efficiency and less discrimination of C-13 under water deficit. This response was associated with greater root development and a better stomatal opening adjustment, especially in the case of Rainbow.
Autores:
Lucena, C. (Autor de correspondencia); Porras, R.; Garcia, M. J.; et al.
Revista:
FRONTIERS IN PLANT SCIENCE
ISSN:
1664-462X
Año:
2019
Vol.:
10
N°:
1237
Iron (Fe) and phosphorus (P) are two essential mineral nutrients whose acquisition by plants presents important environmental and economic implications. Both elements are abundant in most soils but scarcely available to plants. To prevent Fe or P deficiency dicot plants initiate morphological and physiological responses in their roots aimed to specifically acquire these elements. The existence of common signals in Fe and P deficiency pathways suggests the signaling factors must act in conjunction with distinct nutrient-specific signals in order to confer tolerance to each deficiency. Previous works have shown the existence of cross talk between responses to Fe and P deficiency, but details of the associated signaling pathways remain unclear. Herein, the impact of foliar application of either P or Fe on P and Fe responses was studied in P- or Fe-deficient plants of Arabidopsis thaliana, including mutants exhibiting altered Fe or P homeostasis. Ferric reductase and acid phosphatase activities in roots were determined as well as the expression of genes related to P and Fe acquisition. The results obtained showed that Fe deficiency induces the expression of P acquisition genes and phosphatase activity, whereas P deficiency induces the expression of Fe acquisition genes and ferric reductase activity, although only transitorily. Importantly, these responses were reversed upon foliar application of either Fe or P on nutrient-starved plants. Taken together, the results reveal interactions between P- and Fe-related phloem signals originating in the shoots that likely interact with hormones in the roots to initiate adaptive mechanisms to tolerate deficiency of each nutrient.
Revista:
JOURNAL OF SOILS AND SEDIMENTS
ISSN:
1439-0108
Año:
2019
Vol.:
19
N°:
6
Págs.:
2663 - 2664
Revista:
WATER SCIENCE AND TECHNOLOGY: WATER SUPPLY
ISSN:
1606-9749
Año:
2019
Vol.:
19
N°:
6
Págs.:
1735 - 1740
Availability of fresh water for crop irrigation is becoming scarce and rather expensive. In this context, the research about the potential reutilization of non-conventional water sources becomes highly relevant, principally in arid and semi-arid areas. On many occasions, these new water resources involve water with a moderate concentration of salt, making it necessary to improve plant growth under moderate saline conditions. Besides plant breeding techniques, the use of molecules able to improve plant adaptation to saline conditions has great interest. Between these molecules, humic substances (HS) have proven to be efficient as stress-protectors under specific conditions of stress intensity and moment of application. The HS are main components of the soil organic matter and dissolved organic matter resulting from the biotic and abiotic transformation of fresh organic matter in natural ecosystems. Although knowledge about their structure is still under open debate, HS contain aromatic and aliphatic domains presenting O-, N- and S- containing functional groups with high biological and chemical activities. The aim of this presentation is to summarize the main effects of humic acids (HA) applied either on the root or on the shoot, on the metabolism and hormonal balance of plants cultivated under normal and stressing conditions, from studies carried out for our group and collaborations during the last years.
Autores:
Calvo-Polanco, M. (Autor de correspondencia); Armada, E.; Zamarreño, Ángel; et al.
Revista:
JOURNAL OF EXPERIMENTAL BOTANY
ISSN:
0022-0957
Año:
2019
Vol.:
70
N°:
21
Págs.:
6437 - 6446
The relatively better performance of mycorrhizal plants subjected to drought stress has commonly been linked to improved root water uptake through the fungal regulation of plant aquaporins and hormones. In this study, we examined the role of ectomycorrhizal fungi in plant water relations and plant hormonal balance under mild drought using split-root seedlings of Populus trichocarpa x deltoides either with or without inoculation with Laccaria bicolor. The root compartments where the drought treatment was applied had higher ABA and lower cytokinin tZR contents, and greater expression of the plant aquaporins PtPIP1;1, PtPIP1;2, PtPIP2;5, and PtPIP2;7. On the other hand, the presence of L. bicolor within the roots down-regulated PtPIP1;4, PtPIP2;3, and PtPIP2;10, and reduced the abundance of PIP2 proteins. In addition, expression of the fungal aquaporins JQ585595 and JQ585596 were positively correlated with root ABA content, while tZR content was positively correlated with PtPIP1;4 and negatively correlated with PtPIP2;7. The results demonstrate a coordinated plant-fungal system that regulates the different mechanisms involved in water uptake in ectomycorrhizal poplar plants.
Autores:
Foltran, E. C. (Autor de correspondencia); Rocha, J. H. T.; Bazani, J. H.; et al.
Revista:
FOREST ECOLOGY AND MANAGEMENT
ISSN:
0378-1127
Año:
2019
Vol.:
435
Págs.:
170 - 179
Phosphate fertilizers play an important role in plant nutrition. Different P fertilizer sources such as high-solubility (simple superphosphate, SSP), low-solubility (rock phosphate, RP) and complex superphosphate (CSP) are available for plant supplementation. The objective of this study was to investigate the short- and long-term redistribution of soil P after application of different P sources at establishment of an Eucalyptus forest stand. We carried out two experiments to identify the short- and long- term changes in a Brazilian Oxisol. To property identify the P pools in different times, Hadleýs fractionation methodology was applied to a long-term studies and citrate and oxalate to short-term. From zero to 180 days, the soluble P fractions were not altered in the non-fertilized treatment. Under SSP, a slight increase in this P fraction was found until 30 days, followed by a decrease in later evaluations. During the same period, a slight reduction in Pi extracted by citrate and oxalate was found under the control and a large reduction (approximately 50%) under the SSP treatment. Intermediate behavior was observed under the CSP and RP treatments, whereas there was an increase in P-citrate and P-oxalate until 30 days followed by a reduction afterwards. These results suggest that this pool comprises a potential bioavailability of P to plants.
Autores:
Silva-Navas J.; Conesa C.M.; Sáez A.; et al.
Revista:
NEW PHYTOLOGIST (ONLINE)
ISSN:
1469-8137
Año:
2019
Vol.:
224
N°:
1
Págs.:
242 - 257
Phosphate (Pi) is an essential nutrient for all organisms. Roots are underground organs, but the majority of the root biology studies have been done on root systems growing in the presence of light. Root illumination alters the Pi starvation response (PSR) at different intensities. Thus, we have analyzed morphological, transcriptional and physiological responses to Pi starvation in dark-grown roots. We have identified new genes and pathways regulated by Pi starvation that were not described previously. We also show that Pi-starved plants increase the cis-zeatin (cZ) : trans-zeatin (tZ) ratio. Transcriptomic analyses show that tZ preferentially represses cell cycle and PSR genes, whereas cZ induces genes involved in cell and root hair elongation and differentiation. In fact, cZ-treated seedlings show longer root system as well as longer root hairs compared with tZ-treated seedlings, increasing the total absorbing surface. Mutants with low cZ concentrations do not allocate free Pi in roots during Pi starvation. We propose that Pi-starved plants increase the cZ : tZ ratio to maintain basal cytokinin responses and allocate Pi in the root system to sustain its growth. Therefore, cZ acts as a PSR hormone that stimulates root and root hair elongation to enlarge the root absorbing surface and to increase Pi concentrations in roots.
Revista:
PLANT DIRECT
ISSN:
2475-4455
Año:
2019
Vol.:
3
N°:
10
Págs.:
1 - 12
Although the ability of humic (HA) and fulvic acids (FA) to improve plant growth has been demonstrated, knowledge about the mechanisms responsible for the direct effects of HA and FA on the promotion of plant growth is scarce and fragmentary. Our study investigated the causal role of both root PM H+-ATPase activity and ABA in the SHA-promoting action on both root and shoot growth. The involvement of these processes in the regulation of shoot cytokinin concentration and activity was also studied. Our aim was to integrate such plant responses for providing new insights to the current model on the mode of action of HA for promoting root and shoot growth. Experiments employing specific inhibitors and using Cucumis sativus L. plants show that both the root PM H+-ATPase activity and root ABA play a crucial role in the root growth-promoting action of SHA. With regard to the HA-promoting effects on shoot growth, two pathways of events triggered by the interaction of SHA with plant roots are essential for the increase in root PM H+-ATPase activity-which also mediates an increase in cytokinin concentration and action in the shoot-and the ABA-mediated increase in hydraulic conductivity (Lp(r)).
Autores:
Garcia, M. J.; Corpas, F. J. ; Lucena, C.; et al.
Revista:
FRONTIERS IN PLANT SCIENCE
ISSN:
1664-462X
Año:
2018
Vol.:
9
N°:
1325
Ethylene, nitric oxide (NO) and glutathione (GSH) increase in Fe-deficient roots of Strategy I species where they participate in the up-regulation of Fe acquisition genes. However, S-nitrosoglutathione (GSNO), derived from NO and GSH, decreases in Fe-deficient roots. GSNO content is regulated by the GSNO-degrading enzyme S-nitrosoglutathione reductase (GSNOR). On the other hand, there are several results showing that the regulation of Fe acquisition genes does not solely depend on hormones and signaling molecules (such as ethylene or NO), which would act as activators, but also on the internal Fe content of plants, which would act as a repressor. Moreover, different results suggest that total Fe in roots is not the repressor of Fe acquisition genes, but rather the repressor is a Fe signal that moves from shoots to roots through the phloem [hereafter named LOng Distance Iron Signal (LODIS)]. To look further in the possible interactions between LODIS, ethylene and GSNOR, we compared Arabidopsis WT Columbia and LODIS-deficient mutant opt3-2 plants subjected to different Fe treatments that alter LODIS content. The opt3-2 mutant is impaired in the loading of shoot Fe into the phloem and presents constitutive expression of Fe acquisition genes. In roots of both Columbia and opt3-2 plants we determined 1-aminocyclopropane1-carboxylic acid (ACC, ethylene precursor), expression of ethylene synthesis and signaling genes, and GSNOR expression and activity. The results obtained showed that both 'ethylene' (ACC and the expression of ethylene synthesis and signaling genes) and 'GSNOR' (expression and activity) increased in Fe-deficient WT Columbia roots. Additionally, Fe-sufficient opt3-2 roots had higher 'ethylene' and 'GSNOR' than Fe-sufficient WT Columbia roots. The increase of both 'ethylene' and 'GSNOR' was not related to the total root Fe content but to the absence of a Fe shoot signal (LODIS), and was associated with the up-regulation of Fe acquisition genes. The possible relationship between GSNOR(GSNO) and ethylene is discussed.
Revista:
NATURE CHEMICAL BIOLOGY
ISSN:
1552-4450
Año:
2018
Vol.:
14
N°:
2
Págs.:
171 - 178
Biosynthesis of the phytohormone jasmonoyl-isoleucine (JA-Ile) requires reduction of the JA precursor 12-oxo-phytodienoic acid (OPDA) by OPDA reductase 3 (OPR3). Previous analyses of the opr3-1 Arabidopsis mutant suggested an OPDA signaling role independent of JA-Ile and its receptor COI1; however, this hypothesis has been challenged because opr3-1 is a conditional allele not completely impaired in JA-Ile biosynthesis. To clarify the role of OPR3 and OPDA in JA-independent defenses, we isolated and characterized a loss-of-function opr3-3 allele. Strikingly, opr3-3 plants remained resistant to necrotrophic pathogens and insect feeding, and activated COI1-dependent JA-mediated gene expression. Analysis of OPDA derivatives identified 4,5-didehydro-JA in wounded wild-type and opr3-3 plants. OPR2 was found to reduce 4,5-didehydro-JA to JA, explaining the accumulation of JA-Ile and activation of JA-Ile-responses in opr3-3 mutants. Our results demonstrate that in the absence of OPR3, OPDA enters the beta-oxidation pathway to produce 4,5-ddh-JA as a direct precursor of JA and JA-Ile, thus identifying an OPR3-independent pathway for JA biosynthesis.
Revista:
BIOLOGICAL CONTROL
ISSN:
1049-9644
Año:
2018
Vol.:
116
Págs.:
90 - 102
Entomopathogenic fungi have traditionally been assumed to help regulate insect populations. However, some hypocrealean ascomycetes, such as Beauveria bassiana, play other, poorly understood ecological roles that might be useful in developing novel strategies for both increased crop production and crop protection. The primary aims of this work were (a) to assess endophytic colonization of bread wheat and durum wheat plants by the applied fungus B. bassiana strain EABb 04/01-Tip; (b) to examine the impact of various B. bassiana inoculation methods on growth, yield, phytohormone levels and nutrient uptake in the plants, and (c) to quantify mortality of cotton leafworm (Spodoptera littoralis) larvae fed with leaves from inoculated plants. Three experiments involving different inoculation methods (viz., 'soil treatment', 'seed dressing' and 'leaf spraying'), and a fourth experiment to assess mortality in S. littoralis larvae fed with leaves from endophytically-colonized plants, and were conducted according to a completely randomized design. Beauveria bassiana successfully established within, and colonized, bread wheat and durum wheat plants. The fungus was, for the first time, re-isolated from grains produced by plants inoculated using the 'seed dressing' and 'soil treatment' methods. The fungus boosted spike production in bread wheat inoculated using the 'seed dressing' and 'soil treatment' methods, and also in durum wheat but only using the 'soil treatment' method. 'Seed dressing' increased grain yield by about 40%, and also root length, in bread wheat compared with control plants. Mortality in S. littoralis larvae fed with leaves from inoculated plants ranged from 30% using the 'seed dressing' method to 57% using the 'leaf spraying' method compared with 0% when fed the control leaves. However, no fungal outgrowth was detected in larval cadavers. The sustainability of crop production and crop protection strategies based on B. bassiana therefore depends on the effectiveness of the inoculation method and on the particular host plant.
Autores:
Quiroga, G.; Erice, G.; Aroca, R.; et al.
Revista:
AGRICULTURAL WATER MANAGEMENT
ISSN:
0378-3774
Año:
2018
Vol.:
202
Págs.:
271 - 284
Climate change is leading to the intensification of drought effects worldwide, which considerably reduce crop production. A better understanding of the drought-tolerance mechanisms would lead into a more productive agriculture. The arbuscular mycorrhizal (AM) symbiosis has been shown to improve plant tolerance to drought. Salicylic acid (SA) is a phenolic compound involved in many aspects of plant growth and development. Apart from its role in biotic interactions, it is also involved in the regulation of important plant physiological processes, including plant water relations under stressful conditions. However, despite the importance of SA in plant physiology and in AM colonization, little is known about its effect on regulation of root water transport. Thus, the aim of this work was to study the combined effect of AM symbiosis and SA on root hydraulic properties under drought stress, with special focus on how these factors can alter radial root water transport pathways through aquaporin regulation. Also, the crosstalk between SA and other phytohormones was taken into account. Results showed that the AM symbiosis modifies root hydraulic responses to drought episodes. Under these conditions, AM plants showed increased Lpr and Lo. Exogenous SA application decreased Lpr and Lo under drought. SA modulation of water conductivity could be due to a fine-regulation of root aquaporins (as ZmPIP2:4 or ZmTIP1;1). Furthermore, SA application differently modulated the percentage of water flowing by the apoplastic pathway, decreasing its contribution to total root water flow in AM plants and increasing it in non-AM plants. An intricate relationship between Lpr, aquaporins and endogenous levels of SA, ABA and jasmonic acid was observed. Future studies should explore more in detail the crosstalk mechanism between these hormones in the regulation of water transport in AM roots, in order to better understand the mechanism through which the AM symbiosis copes with drought stress. (C) 2017 Elsevier B.V. All rights reserved.
Autores:
Fuentes, M; Bacaicoa, E.; Rivero, M.; et al.
Revista:
FRONTIERS IN PLANT SCIENCE
ISSN:
1664-462X
Año:
2018
Vol.:
9
Págs.:
351
Iron deficiency in plants is caused by a low availability of iron in the soil, and its main visual symptom is leaf yellowing due to a decrease in chlorophyll content, along with a reduction in plant growth and fruit quality. Foliar sprays with Fe compounds are an economic alternative to the treatment with expensive synthetic Fe-chelates applied to the soil, although the efficacy of foliar treatments is rather limited. Generally, plant response to Fe-foliar treatments is monitored by measuring chlorophyll content (or related parameters as SPAD index). However, different studies have shown that foliar Fe sprays cause a local regreening and that translocation of the applied Fe within the plant is quite low. In this context, the aim of this study was to assess the effects of foliar applications of different Fe compounds [FeSO4, Fe(III)-EDTA, and Fe(III)-heptagluconate] on Fe-deficient cucumber plants, by studying the main physiological plant root responses to Fe deficiency [root Fe(III) chelate reductase (FCR) activity; acidification of the nutrient solution; and expression of the Fe deficiency responsive genes encoding FCR, CsFRO1, Fe(II) root transporter CsIRT1, and two plasma membrane H+-ATPases, CsHA1 and CsHA2], along with SPAD index, plant growth and Fe content. The results showed that the overall assessment of Fe-deficiency root responses improved the evaluation of the efficacy of the Fe-foliar treatments compared to just monitoring SPAD indexes. Thus, FCR activity and expression of Fe-deficiency response genes, especially CsFRO1 and CsHA1, preceded the trend of SPAD index and acted as indicators of whether the plant was sensing or not metabolically active Fe due to the treatments. Principal component analysis of the data also provided a graphical tool to evaluate the evolution of plant responses to foliar Fe treatments with time.
Revista:
APPLIED SOIL ECOLOGY
ISSN:
0929-1393
Año:
2018
Vol.:
123
Págs.:
521 - 537
The ability of rhizospheric humic substances to improve plant growth has been well established by many studies carried out using diverse plant species cultivated under many different conditions. These beneficial effects of humic substances on plant development are expressed in both root and shoot. However, the mechanisms responsible for this action of humic substances are only partially known and poorly integrated. In fact, although the studies focused on plant root development are numerous, those dealing with plant shoot development are scarce. Likewise, studies integrating humic effects on root and shoot are also few. In this context, the main goal of this work is to summarize some of the results regarding the effects of humic substances on plant development within a hypothetical holistic framework that will allow us to interconnect these findings and disclose some features of the functional crosstalk between the effects on soil, root and shoot. Furthermore, the significance of all these mechanisms in plants growing in the field is also discussed.
Autores:
Sanchez-Romera, B.; Calvo-Polanco, M.; Ruiz-Lozano, J. M.; et al.
Revista:
PLANT AND CELL PHYSIOLOGY
ISSN:
0032-0781
Año:
2018
Vol.:
59
N°:
2
Págs.:
248 - 261
Jasmonic acid (JA) and arbuscular mycorrhizal (AM) symbioses are known to protect plants against abiotic and biotic stresses, but are also involved in the regulation of root hydraulic conductance (L). The objective of this experiment was to elucidate the role of JA in the water relations and hormonal regulation of AM plants under drought by using tomato plants defective in the synthesis of JA (def-1). Our results showed that JA is involved in the uptake and transport of water through its effect on both physiological parameters (stomatal conductance and L) and molecular parameters, mainly by controlling the expression and abundance of aquaporins. We observed that def-1 plants increased the expression of seven plant aquaporin genes under well-watered conditions in the absence of AM fungus, which partly explain the increment of L by this mutation under well-watered conditions. In addition, the effects of the AM symbiosis on plants were modified by the def-1 mutation, with the expression of some aquaporins and plant hormone concentration being disturbed. On the other hand, methyl salicylate (MeSA) content was increased in non-mycorrhizal def-1 plants, suggesting that MeSA and JA can act together in the regulation of L. In a complementary experiment, it was found that exogenous MeSA increased L, confirming our hypothesis. Likewise, we confirmed that JA, ABA and SA are hormones involved in plant mechanisms to cope with stressful situations, their concentrations being controlled by the AM symbiosis. In conclusion, under well-watered conditions, the def-1 mutation mimics the effects of AM symbiosis, but under drought conditions the def-1 mutation changed the effects of the AM symbiosis on plants.
Revista:
NATURE CHEMICAL BIOLOGY
ISSN:
1552-4450
Año:
2018
Vol.:
14
N°:
5
Págs.:
480 - 488
The phytohormone jasmonoyl-isoleucine (JA-Ile) regulates defense, growth and developmental responses in vascular plants. Bryophytes have conserved sequences for all JA-Ile signaling pathway components but lack JA-Ile. We show that, in spite of 450 million years of independent evolution, the JA-Ile receptor COI1 is functionally conserved between the bryophyte Marchantia polymorpha and the eudicot Arabidopsis thaliana but COI1 responds to different ligands in each species. We identified the ligand of Marchantia MpCOI1 as two isomeric forms of the JA-Ile precursor dinor-OPDA (dinor-cis-OPDA and dinor-iso-OPDA). We demonstrate that AtCOI1 functionally complements Mpcoi1 mutation and confers JA-Ile responsiveness and that a single-residue substitution in MpCOI1 is responsible for the evolutionary switch in ligand specificity. Our results identify the ancestral bioactive jasmonate and clarify its biosynthetic pathway, demonstrate the functional conservation of its signaling pathway, and show that JA-Ile and COI1 emergence in vascular plants required co-evolution of hormone biosynthetic complexity and receptor specificity.
Revista:
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
ISSN:
0021-8561
Año:
2018
Vol.:
66
N°:
19
Págs.:
4787 - 4799
This study describes the efficiency of a new coating material for preparing granulated potassium-fertilizers with a potassium release to the soil solution sensitive to rainfall intensity. The composite is prepared by reaction of an alkyd-resin with cement in the absence of water. The complementary use of diverse analytical techniques showed that the presence of the cement fraction induced alkyd resin reticulation and gradual cement-resin hardening. Scanning electron microscopy revealed the formation of micro and nanopores within cement-clusters, whose water permeability is affected by the resin reticulation and amphiphilic character. Potassium release was evaluated in water, soil-columns, and in soil-plant trials in pots and open-field. Agronomic results were consistent with potassium release rates obtained in water solution and soil columns. The composite-coated potassium fertilizer was more efficient than the noncoated one in providing plant available potassium, with this effect being dependent on water presence in soil.
Revista:
JOURNAL OF SOILS AND SEDIMENTS
ISSN:
1439-0108
Año:
2018
Vol.:
18
N°:
4
Págs.:
1389 - 1399
The traditional method to determine humic content (humic and fulvic acids) in commercial fertilizers, biostimulants, and organic materials is based on the oxidation of the organic carbon contained in the basic-soluble but acid-insoluble fraction (humic acids) and the basic-acid soluble fraction (fulvic acids) of their alkaline water extracts. This methodology, merely operational, makes it impossible to distinguish if the quantified carbon corresponds to substances with "humic" chemical nature or to non-humic organic matter but with similar solubility properties to those of humic matter. The aim of this work is to develop a new methodology that not only quantifies the humic content in commercial products (and raw materials) but also assesses the humic quality of the quantified organic matter. To this end, humic and fulvic (-like) fractions have been isolated/purified from several humic and non-humic materials and characterized by means of elemental analysis and UV-visible, fluorescence, and infrared spectroscopies, and these data have been used to perform a discriminant analysis (DA). The model obtained from the DA is able to discriminate humic and fulvic fractions from apparently humic or fulvic ones and provides discriminant classification functions that have proven to successfully predict the "humic quality" of the fractions isolated from commercial products, after their elemental and spectroscopic characterization. Therefore, the combination of the fractionation, characterization, and evaluation by the DA is proposed as an effective methodology for quantifying and assessing the quality of the humic content claimed in the labels of commercial products.
Revista:
BMC PLANT BIOLOGY
ISSN:
1471-2229
Año:
2018
Vol.:
18
N°:
105
Págs.:
14
Background: The release of phytosiderephores (PS) to the rhizosphere is the main root response to iron (Fe) deficiency in graminaceous plants. We have investigated the role of the Fe status in the shoot as well as of the signaling pathways controlled by three relevant phytoregulators-indolacetic acid (IAA), ethylene and nitric oxide (NO) - in the regulation of this root response in Fe-starved wheat plants. To this end, the PS accumulation in the nutrient solution and the root expression of the genes encoding the nicotianamine aminotransferase (TaNAAT) and ferritin (TaFER) have been evaluated in plants subjected to different treatments. Results: The application of Fe to leaves of Fe-deficient plants prevented the increase in both PS root release and TaNAAT gene expression thus showing the relevant role of the shoot to root communication in the regulation of PS root release and some steps of PS biosynthesis. Experiments with specific hormone inhibitors showed that while ethylene and NO did not positively regulate Fe deficiency induced PS root release, auxin plays an essential role in the regulation of this process. Moreover, the application of IM to Fe-sufficient plants promoted both PS root release and TaNAAT gene expression thus indicating that auxin might be involved in the shoot to root signaling network regulating Fe-deficiency root responses in wheat Conclusions: These results therefore indicate that PS root release in Fe-deficient wheat plants is directly modulated by the shoot Fe status through signaling pathways involving, among other possible effectors, auxin.
Autores:
Garcia, A. C. (Autor de correspondencia); Tavares, O. C. H.; Balmori, D. M.; et al.
Revista:
JOURNAL OF SOILS AND SEDIMENTS
ISSN:
1439-0108
Año:
2018
Vol.:
18
N°:
4
Págs.:
1365 - 1375
The use of humic substances (HS) in agriculture is beneficial and has positive environmental impacts. However, to optimize the use of HS possible links between their structural characteristics and bioactivity must be shown. The goal of this study is to evaluate the bioactivity of different humic fractions extracted from vermicompost (VC) in rice plants and to shed light to possible structure-function relationships. Humic-like fractions were obtained from cattle manure vermicompost processed by African nightcrawlers (Eudrilus eugeniae spp.). Humic-like acid fraction using only water as extractor (HLAw), HLA fraction extracted following the International Humic Substances Society (IHSS) recommended method, and the solid residue (humified residual (HR)) after extraction of HLA were characterized using complementary chemical, physic, and spectroscopic technics (elemental composition, UV-Vis and Fourier transform infrared spectroscopy (FTIR) spectroscopies, C-13-CP MAS NMR, and MEV). Biological activity of the three HS was conducted in growth chambers and measured in roots using WinRhizo Arabidopsis software. Principal component analysis (PCA) was used to find a grouping pattern between the structural variables evaluated and the obtained root parameters. Differences were found in elemental composition among HS with larger C/N ratio in HR than in HLA and HLAw. HLA and HLAw FTIR spectra showed carboxyl band at 1714.66 cm(-1) better resolved than in HR. Bands at 1642 cm(-1) (amide I) and 1510 cm(-1) (lignin), were better resolved in HLA. C-13-NMR showed the following order of aromaticity: HLA > HLAw > HR. For HLAw bioactivity, the structures C-Alkyl-H,C-R, C-C=O, and C-COO-H,C-R correlated with the number and growth of smaller root. The aromatic C-Ar-H,C-R, C-Ar-O,C-N, and aliphatic C-Alkyl-O,C-N, CAlkyl-O, and CAlkyl-di-O structures in HLA, correlated with larger roots growth. HR also stimulated root growth and development in rice plants. Aliphatic and oxygenated structures in HLAw showed a relation with induction of initial root emissions, whereas the presence of aromatic compounds in HLA was related with root growth stimulation activity. Higher concentration of HLAw was necessary to produce an equivalent stimulus compared with HLA; it could indicate that, although both fractions showed similar types of structures in their composition, differences in the predominant structures may be determining different effects on the root.
Autores:
Calvo-Polanco, M.; Ibort, P.; Molina, S.; et al.
Revista:
PLANTA
ISSN:
0032-0935
Año:
2017
Vol.:
246
N°:
5
Págs.:
987 - 997
The effect of ethylene and its precursor ACC on root hydraulic properties, including aquaporin expression and abundance, is modulated by relative air humidity and plant sensitivity to ethylene. Relative air humidity (RH) is a main factor contributing to water balance in plants. Ethylene (ET) is known to be involved in the regulation of root water uptake and stomatal opening although its role on plant water balance under different RH is not very well understood. We studied, at the physiological, hormonal and molecular levels (aquaporins expression, abundance and phosphorylation state), the plant responses to exogenous 1-aminocyclopropane-1-carboxylic acid (ACC; precursor of ET) and 2-aminoisobutyric acid (AIB; inhibitor of ET biosynthesis), after 24 h of application to the roots of tomato wild type (WT) plants and its ET-insensitive never ripe (nr) mutant, at two RH levels: regular (50%) and close to saturation RH. Highest RH induced an increase of root hydraulic conductivity (Lp(o)) of non-treated WT plants, and the opposite effect in nr mutants. The treatment with ACC reduced Lp(o) in WT plants at low RH and in nr plants at high RH. The application of AIB increased Lp(o) only in nr plants at high RH. In untreated plants, the RH treatment changed the abundance and phosphorylation of aquaporins that affected differently both genotypes according to their ET sensitivity. We show that RH is critical in regulating root hydraulic properties, and that Lp(o) is affected by the plant sensitivity to ET, and possibly to ACC, by regulating aquaporins expression and their phosphorylation status. These results incorporate the relationship between RH and ET in the response of Lp(o) to environmental changes.
Autores:
Manzano, C.; Pallero-Baena, M.; J.; et al.
Revista:
JOURNAL OF EXPERIMENTAL BOTANY
ISSN:
0022-0957
Año:
2017
Vol.:
68
N°:
18
Págs.:
5103 - 5116
Plant roots have the potential capacity to grow almost indefinitely if meristematic and lateral branching is sustained. In a genetic screen we identified an Arabidopsis mutant showing limited root growth (lrg1) due to defects in cell division and elongation in the root meristem. Positional cloning determined that lrg1 affects an alpha-1,2-mannosyltransferase gene, LEW3, involved in protein N-glycosylation. The lrg1 mutation causes a synonymous substitution that alters the correct splicing of the fourth intron in LEW3, causing a mix of wild-type and truncated protein. LRG1 RNA missplicing in roots and short root phenotypes in lrg1 are light-intensity dependent. This mutation disrupts a GC-base pair in a three-base-pair stem with a four-nucleotide loop, which seems to be necessary for correct LEW3 RNA splicing. We found that the lrg1 short root phenotype correlates with high levels of reactive oxygen species and low pH in the apoplast. Proteomic analyses of N-glycosylated proteins identified GLU23/PYK10 and PRX34 as N-glycosylation targets of LRG1 activity. The lrg1 mutation reduces the positive interaction between Arabidopsis and Serendipita indica. A prx34 mutant showed a significant reduction in root growth, which is additive to lrg1. Taken together our work highlights the important role of N-glycosylation in root growth and development.
Autores:
Kulikova, N. A.; Polyakov, A. Y.; Lebedev, V. A. ; et al.
Revista:
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
ISSN:
0021-8561
Año:
2017
Vol.:
65
N°:
51
Págs.:
11157 - 11169
Availability of Fe in soil to plants is closely related to the presence of humic substances (HS). Still, the systematic data on applicability of iron-based nanomaterials stabilized with HS as a source for plant nutrition are missing. The goal of our study was to establish a connection between properties of iron-based materials stabilized by HS and their bioavailability to plants. We have prepared two samples of leonardite HS-stabilized iron-based materials with substantially different properties using the reported protocols and studied their physical chemical state in relation to iron uptake and other biological effects. We used Mossbauer spectroscopy, XRD, SAXS, and TEM to conclude on iron speciation, size, and crystallinity. One material (Fe-HA) consisted of polynuclear iron(III) (hydr)oxide complexes, so-called ferric polymers, distributed in HS matrix. These complexes are composed of predominantly amorphous small-size components (<5 nm) with inclusions of larger crystalline particles (the mean size of (11 4) nm). The other material was composed of well-crystalline feroxyhyte (delta'-FeOOH) NPs with mean transverse sizes of (35 20) nm stabilized by small amounts of HS. Bioavailability studies were conducted on wheat plants under conditions of iron deficiency. The uptake studies have shown that small and amorphous ferric polymers were readily translocated into the leaves on the level of Fe-EDTA, whereas relatively large and crystalline feroxyhyte NPs were mostly sorbed on the roots. The obtained data are consistent with the size exclusion limits of cell wall pores (5-20 nm). Both samples demonstrated distinct beneficial effects with respect to photosynthetic activity and lipid biosynthesis. The obtained results might be of use for production of iron-based nanomaterials stabilized by HS with the tailored iron availability to plants. They can be applied as the only source for iron nutrition as well as in combination with the other elements, for example, for industrial production of "nanofortified" macrofertilizers (NPK).
Autores:
Ibort, P.; Molina, S.; Nunez, R.; et al.
Revista:
ANNALS OF BOTANY
ISSN:
0305-7364
Año:
2017
Vol.:
120
N°:
1
Págs.:
101 - 122
Background and Aims Plant growth-promoting bacteria (PGPB) are soil micro-organisms able to interact with plants and stimulate their growth, positively affecting plant physiology and development. Although ethylene plays a key role in plant growth, little is known about the involvement of ethylene sensitivity in bacterial inoculation effects on plant physiology. Thus, the present study was pursued to establish whether ethylene perception is critical for plant-bacteria interaction and growth induction by two different PGPB strains, and to assess the physiological effects of these strains in juvenile and mature tomato (Solanum lycopersicum) plants. Methods An experiment was performed with the ethylene-insensitive tomato never ripe and its isogenic wildtype line in which these two strains were inoculated with either Bacillus megaterium or Enterobacter sp. C7. Plants were grown until juvenile and mature stages, when biomass, stomatal conductance, photosynthesis as well as nutritional, hormonal and metabolic statuses were analysed. Key Results Bacillus megaterium promoted growth only in mature wild type plants. However, Enterobacter C7 PGPB activity affected both wild-type and never ripe plants. Furthermore, PGPB inoculation affected physiological parameters and root metabolite levels in juvenile plants; meanwhile plant nutrition was highly dependent on ethylene sensitivity and was altered at the mature stage. Bacillus megaterium inoculation improved carbon assimilation in wild-type plants. However, insensitivity to ethylene compromised B. megaterium PGPB activity, affecting photosynthetic efficiency, plant nutrition and the root sugar content. Nevertheless, Enterobacter C7 inoculation modified the root amino acid content in addition to stomatal conductance and plant nutrition. Conclusions Insensitivity to ethylene severely impaired B. megaterium interaction with tomato plants, resulting in physiological modifications and loss of PGPB activity. In contrast, Enterobacter C7 inoculation stimulated growth independently of ethylene perception and improved nitrogen assimilation in ethylene-insensitive plants. Thus, ethylene sensitivity is a determinant for B. megaterium, but is not involved in Enterobacter C7 PGPB activity.
Revista:
ENVIRONMENTAL AND EXPERIMENTAL BOTANY
ISSN:
0098-8472
Año:
2017
Vol.:
143
Págs.:
10 - 19
The use of plant growth promoting rhizobacteria (PGPR) is a proven management strategy to improve plant growth. The aim was to reveal the genomic and proteomic basis of the plant tolerance to saline soil conditions. Combination of whole transcriptome analysis and proteomic profiling helped further the understanding of the complexity of salt tolerance responses. Arabidopsis plants were grown inoculated or not with Bacillus megaterium and irrigated or not with salt. Physiological, genomic and proteomic approaches were combined to reveal plant salt tolerance mechanisms. Microarray analyses revealed the up-regulation of the jasmonic acid metabolism (CYP94B3, lipooxigenase 4 and allene-oxide cyclase) under saline conditions. Knock-out mutants of the gene of interest CYP94B3, responsible of JA-Ile catabolism, were used to confirm the obtained results. Salinity resulted in leaf Na accumulation with decreased chlorophyll content, but PGPR inoculation helped to overcome the stress. Proteomic analysis showed enhanced monodehydroascorbate reductase (MDHAR) content together with ATP synthase. CYP94B3 knock-out plants confirmed the key role of JA-Ile turnover to overcome moderate saline stress. Subsequent experimentation showed that CYP94B3 was important for salt tolerance under moderate and severe salt stress. Inoculation with B. megaterium was a valuable tool to reveal the importance of JA-Ile turnover and to recover Arabidopsis plants from saline stress.
Revista:
MYCORRHIZA
ISSN:
0940-6360
Año:
2016
Vol.:
26
N°:
2
Págs.:
111 - 122
Hormonal regulation and symbiotic relationships provide benefits for plants to overcome stress conditions. The aim of this study was to elucidate the effects of exogenous methyl jasmonate (MeJA) application on root hydraulic conductivity (L) of Phaseolus vulgaris plants which established arbuscular mycorrhizal (AM) symbiosis under two water regimes (well-watered and drought conditions). The variation in endogenous contents of several hormones (MeJA, JA, abscisic acid (ABA), indol-3-acetic acid (IAA), salicylic acid (SA)) and the changes in aquaporin gene expression, protein abundance and phosphorylation state were analyzed. AM symbiosis decreased L under well-watered conditions, which was partially reverted by the MeJA treatment, apparently by a drop in root IAA contents. Also, AM symbiosis and MeJA prevented inhibition of L under drought conditions, most probably by a reduction in root SA contents. Additionally, the gene expression of two fungal aquaporins was upregulated under drought conditions, independently of the MeJA treatment. Plant aquaporin gene expression could not explain the behaviour of L. Conversely, evidence was found for the control of L by phosphorylation of aquaporins. Hence, MeJA addition modified the response of L to both AM symbiosis and drought, presumably by regulating the root contents of IAA and SA and the phosphorylation state of aquaporins.
Revista:
PLANT CELL AND ENVIRONMENT
ISSN:
0140-7791
Año:
2016
Vol.:
39
N°:
2
Págs.:
441 - 522
Arbuscular mycorrhizal (AM) symbiosis alleviates drought stress in plants. However, the intimate mechanisms involved, as well as its effect on the production of signalling molecules associated with the host plant-AM fungus interaction remains largely unknown. In the present work, the effects of drought on lettuce and tomato plant performance and hormone levels were investigated in non-AM and AM plants. Three different water regimes were applied, and their effects were analysed over time. AM plants showed an improved growth rate and efficiency of photosystem II than non-AM plants under drought from very early stages of plant colonization. The levels of the phytohormone abscisic acid, as well as the expression of the corresponding marker genes, were influenced by drought stress in non-AM and AM plants. The levels of strigolactones and the expression of corresponding marker genes were affected by both AM symbiosis and drought. The results suggest that AM symbiosis alleviates drought stress by altering the hormonal profiles and affecting plant physiology in the host plant. In addition, a correlation between AM root colonization, strigolactone levels and drought severity is shown, suggesting that under these unfavourable conditions, plants might increase strigolactone production in order to promote symbiosis establishment to cope with the stress.
Autores:
R; B; Urarte, E; et al.
Revista:
FRONTIERS IN PLANT SCIENCE
ISSN:
1664-462X
Año:
2016
Vol.:
7
Págs.:
140
We aimed to identify the early stress response and plant performance of Medicago truncatula growing in axenic medium with ammonium or urea as the sole source of nitrogen, with respect to nitrate-based nutrition. Biomass measurements, auxin content analyses, root system architecture (RSA) response analyses, and physiological parameters were determined. Both ammonium and ureic nutrition severely affected the RSA, resulting in changes in the main elongation rate, lateral root development, and insert position from the root base. The auxin content decreased in both urea- and ammonium-treated roots; however, only the ammonium-treated plants were affected at the shoot level. The analysis of chlorophyll a fluorescence transients showed that ammonium affected photosystem II, but urea did not impair photosynthetic activity. Superoxide dismutase isoenzymes in the plastids were moderately affected by urea and ammonium in the roots. Overall, our results showed that low N doses from different sources had no remarkable effects on M. truncatula, with the exception of the differential phenotypic root response. High doses of both ammonium and urea caused great changes in plant length, auxin contents and physiological measurements. Interesting correlations were found between the shoot auxin pool and both plant length and the "performance index" parameter, which is obtained from measurements of the kinetics of chlorophyll a fluorescence.
Autores:
T.C.; G.; C.; et al.
Revista:
PLANT PHYSIOLOGY
ISSN:
0032-0889
Año:
2016
Vol.:
171
N°:
2
Págs.:
1418 - 1426
The presence of arsenic in soil and water is a constant threat to plant growth in many regions of the world. Phytohormones act in the integration of growth control and stress response, but their role in plant responses to arsenic remains to be elucidated. Here, we show that arsenate [As(V)], the most prevalent arsenic chemical species in nature, causes severe depletion of endogenous cytokinins (CKs) in the model plant Arabidopsis (Arabidopsis thaliana). We found that CK signaling mutants and transgenic plants with reduced endogenous CK levels showed an As(V)-tolerant phenotype. Our data indicate that in CK-depleted plants exposed to As(V), transcript levels of As(V)/phosphate-transporters were similar or even higher than in wild-type plants. In contrast, CK depletion provoked the coordinated activation of As(V) tolerance mechanisms, leading to the accumulation of thiol compounds such as phytochelatins and glutathione, which are essential for arsenic sequestration. Transgenic CK-deficient Arabidopsis and tobacco lines show a marked increase in arsenic accumulation. Our findings indicate that CK is an important regulatory factor in plant adaptation to arsenic stress.
Revista:
FRONTIERS IN PLANT SCIENCE
ISSN:
1664-462X
Año:
2016
Vol.:
6
N°:
1131
Autores:
S; JJ; A; et al.
Revista:
PLANT AND SOIL
ISSN:
0032-079X
Año:
2016
Vol.:
402
Págs.:
27 - 45
Aims: Using Fe- and Mn-deficient Solanum lycopersicum plants, we investigated the effects of Fe and Mn foliar fertilisers, either individually or combined, on plant biomass, leaf chlorophyll and metal micronutrient levels in leaves and roots.
Methods: Plants were grown in hydroponics with different combinations of 0 or 45 ¿M Fe and 0 or 4.6 ¿M Mn. Foliar fertiliser formulations (9 mM FeSO4 and/or 3 mM MnSO4, supplemented with a surfactant) were applied in three consecutive doses. Fertilisation was applied to the first three leaf levels, while upper leaf levels were left untreated.
Results: Iron and Mn deficiency led to characteristic symptoms. Foliar treatments increased concentrations of Fe and Mn, biomass and chlorophyll in treated leaves, although re-greening was incomplete. Approximately 11¿12 % of the Fe increase was in roots (likely mediated via phloem transport), but no Fe increase occurred in untreated leaves. Regarding Mn, a 2 % increase occurred in untreated leaves, but no increase occurred in roots.
Conclusions Iron fertilisation was effective not only in leaves treated with the fertiliser but also in roots, whereas Mn fertilisation had major effects on treated leaves and minor effects on untreated ones. The combined application of Fe + Mn was not detrimental to Fe- or Mn-deficient plants.
Autores:
V.; Maillard, A.; Coquete, L.; et al.
Revista:
PLANT PHYSIOLOGY AND BIOCHEMISTRY
ISSN:
0981-9428
Año:
2016
Vol.:
107
Págs.:
337 - 343
In order to cope with variable mineral nutrient availability, higher plants have developed numerous strategies including the remobilization of nutrients from source to sink tissues. However, such processes remain relatively unknown for magnesium (Mg), which is the third most important cation in plant tissues. Using Mg depletion of Brassica napus, we have demonstrated that Mg is remobilized from old leaves to young shoot tissues. Moreover, this study showed that Mg depletion induces modification of nutrient uptake, especially Zn and Mn. Finally, comparative proteomic analysis of old leaves (source of Mg) revealed amongst other results that some proteins requiring Mg for their functionality (isocitrate dehydrogenase for example) were up-regulated. Moreover, down-regulation of proteases suggested that mobilization of Mg from old leaves was not associated with senescence.
Autores:
RV; R; P; et al.
Revista:
RENEWABLE AGRICULTURE AND FOOD SYSTEMS
ISSN:
1742-1705
Año:
2016
Vol.:
31
N°:
5
Págs.:
402 - 413
A 3-year (2011-2013) field trial was carried out in a mature vineyard (Vitis vinifera L., cv. Sangiovese), planted in 2003, to assess physiological responses of grapevines to biodynamic management. Starting in 2007, the vineyard was managed with organic production protocols in accordance with EC Regulations (834/2007). In 2008, the vineyard (2 ha) was divided in two large plots, with each plot having similar soil physico-chemical properties. One of the plots was managed with organic protocols per EC Regulations and the other with biodynamic practices, consisting of spray application of preparations 500, 500 K, fladen and 501. During the 2011-2013 season, the biodynamic preparations were used at least twice per year, with the exception of 501 that was applied only once in 2013. Concentration of hormones and mineral elements in biodynamic preparations were determined. Biodynamically managed vines showed lower stomatal conductance in all years and lower leaf water potential in 2012. Leaf photosynthetic activity was not influenced by cultivation method. Biodynamic management led to an increase in leaf enzymatic activities of endochitinase (EC 3.2.1.14), exochitinase (ß-N-acetylhexosaminidase, EC 3.2.1.52 and chitin 1,4-ß-chitobiosidase) and ß-1,3-glucanase (EC 3.2.1.39), which are typically correlated with plant biotic and abiotic stresses and associated with induced plant resistance.
Autores:
Galantini, J. A. (Autor de correspondencia); Duval, M.; Martinez, J. M.; et al.
Revista:
INTERNATIONAL JOURNAL OF PLANT AND SOIL SCIENCE
ISSN:
2320-7035
Año:
2016
Vol.:
10
N°:
5
Págs.:
1 - 12
Aims: The aim of this study was to evaluate the long-term effect of tillage systems on the quantity and quality of organic carbon fractions at different soil layers. Study Design: The experimental design was a split plot with three blocks. The long-term effects (25 years) of conventional- (CT) and no-tillage (NT) systems on a Tipic Argiudoll was sampled at 0-5, 5-10, 10-15 and 15-20 cm soil depth. Place and Duration of Study: The field experiment was carried out at Tornquist (38° 07' 06'' S - 62°02' 17'' O) and soil sampling was performed during wheat seeding (June 2011). Methodology: Total soil organic carbon (SOC) content and the following fractions were determined: Coarse particulate (POCc, 105-2000 µm), fine particulate (POCf, 53-105 µm) and mineral-associated (MOC, 0-53 µm) carbon fractions; humic (HA) and fulvic (FA) acids; and total (CHt) and soluble (CHs) carbohydrates. The main physico-chemical properties of HA and FA were analyzed using both FT-IR and fluorescence spectroscopies. Results: After 25 years, total SOC at the 0-20 cm depth was 9% higher in no-tilled than in tilled soils. The POCf was the SOM fraction that turned out to be the most sensitive to tillage effects. The POCc:POCf:MOC ratio at 0-20 cm was similar for NT (3:14:82) and CT (5:10:84); however, differences were found across soil depths. Tilled soils showed higher aromaticity, starting by CH-degradation, in more superficial soil layers.
Autores:
AC (Autor de correspondencia); LG; MG; et al.
Revista:
SCIENTIFIC REPORTS
ISSN:
2045-2322
Año:
2016
Vol.:
6
N°:
20798
Knowledge of the structure-property-function relationship of humic substances (HSs) is key for understanding their role in soil. Despite progress, studies on this topic are still under discussion. We analyzed 37 humic fractions with respect to their isotopic composition, structural characteristics, and properties responsible for stimulating plant root parameters. We showed that regardless of the source of origin of the carbon (C3 or C4), soil-extracted HSs and humic acids (HAs) are structurally similar to each other. The more labile and functionalized HS fraction is responsible for root emission, whereas the more recalcitrant and less functionalized HA fraction is related to root growth. Labile structures promote root stimulation at lower concentrations, while recalcitrant structures require higher concentrations to promote a similar stimulus. These findings show that lability and recalcitrance, which are derived properties of humic fractions, are related to the type and intensity of their bioactivity. In summary, the comparison of humic fractions allowed a better understanding of the relationship between the source of origin of plant carbon and the structure, properties, and type and intensity of the bioactivity of HSs in plants. In this study, scientific concepts are unified and the basis for the agronomic use of HSs is established.
Revista:
EURASIAN SOIL SCIENCE
ISSN:
1064-2293
Año:
2016
Vol.:
49
N°:
10
Págs.:
1099 - 1108
The effect of humic acids (HAs) and their iron complexes (Fe¿HAs) on the input of the main mineral elements into wheat seedlings, as well as on the efficiency of photosynthesis and the lipid profile of plants, under iron deficiency has been studied. The input of iron from Fe¿HA complexes and its predominant accumulation in roots are demonstrated. It is found that HAs increase the efficiency of photosynthesis due to enhanced electron transport in photosystem II. It is shown that the application of HAs and Fe¿HAs is accompanied by an enhanced input of Zn into plants, which could increase the antioxidant status of plants under iron deficiency conditions. In addition, a pronounced increase in the content of lipids in plants is revealed, which is indicative of the effect of HAs on plant metabolism. The obtained results suggest that the positive effect of Fe¿HAs and HAs on plants under iron deficiency conditions is due to a combination of factors, among which the effect of HAs on the antioxidant status of plants and the plant lipid metabolism predominates.
Autores:
A.C.; L.A.; L.G.; et al.
Revista:
JOURNAL OF PLANT PHYSIOLOGY
ISSN:
0176-1617
Año:
2016
Vol.:
192
Págs.:
56 - 63
This work aims to determine the reactive oxygen species (ROS) accumulation, gene expression, anti-oxidant enzyme activity, and derived effects on membrane lipid peroxidation and certain stress markers (proline and malondialdehyde-MDA) in the roots of unstressed and PEG-stressed rice plants associated with vermicompost humic acid (VCHA) application. The results show that the application of VCHA to the roots of unstressed rice plants caused a slight but significant increase in root ROS accumulation and the gene expression and activity of the major anti-oxidant enzymes (superoxide dismutase and peroxidase). This action did not have negative effects on root development, and an increase in both root growth and root proliferation occurred. However, the root proline and MDA concentrations and the root permeability results indicate the development of a type of mild stress associated with VCHA application. When VCHA was applied to PEG-stressed plants, a clear alleviation of the inhibition in root development linked to PEG-mediated osmotic stress was observed. This was associated with a reduction in root ROS production and anti-oxidant enzymatic activity caused by osmotic stress. This alleviation of stress caused by VCHA was also reflected as a reduction in the PEG-mediated concentration of MDA in the root as well as root permeability.
Revista:
PLANT PHYSIOLOGY
ISSN:
0032-0889
Año:
2015
Vol.:
169
N°:
4
Págs.:
2587 - 2596
The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments using cucumber (Cucumis sativus) plants show that the shoot growth enhancement caused by a structurally well-characterized humic acid with sedimentary origin is functionally associated with significant increases in abscisic acid (ABA) root concentration and root hydraulic conductivity. Complementary experiments involving a blocking agent of cell wall pores and water root transport (polyethylenglycol) show that increases in root hydraulic conductivity are essential in the shoot growth-promoting action of the model humic acid. Further experiments involving an inhibitor of ABA biosynthesis in root and shoot (fluridone) show that the humic acid-mediated enhancement of both root hydraulic conductivity and shoot growth depended on ABA signaling pathways. These experiments also show that a significant increase in the gene expression of the main root plasma membrane aquaporins is associated with the increase of root hydraulic conductivity caused by the model humic acid. Finally, experimental data suggest that all of these actions of model humic acid on root functionality, which are linked to its beneficial action on plant shoot growth, are likely related to the conformational structure of humic acid in solution and its interaction with the cell wall at the root surface.
Autores:
J.; M.A.; C.; et al.
Revista:
PLANT JOURNAL
ISSN:
0960-7412
Año:
2015
Vol.:
84
Págs.:
244 - 255
In nature roots grow in the dark and away from light (negative phototropism). However, most current research in root biology has been carried out with the root system grown in the presence of light. Here, we have engineered a device, called Dark-Root (D-Root), to grow plants in vitro with the aerial part exposed to the normal light/dark photoperiod while the roots are in the dark or exposed to specific wavelengths or light intensities. D-Root provides an efficient system for cultivating a large number of seedlings and easily characterizing root architecture in the dark. At the morphological level, root illumination shortens root length and promotes early emergence of lateral roots, therefore inducing expansion of the root system. Surprisingly, root illumination also affects shoot development, including flowering time. Our analyses also show that root illumination alters the proper response to hormones or abiotic stress (e.g. salt or osmotic stress) and nutrient starvation, enhancing inhibition of root growth. In conclusion, D-Root provides a growing system closer to the natural one for assaying Arabidopsis plants, and therefore its use will contribute to a better understanding of the mechanisms involved in root development, hormonal signaling and stress responses.
Autores:
E.; P.; A.; et al.
Revista:
JOURNAL OF EXPERIMENTAL BOTANY
ISSN:
0022-0957
Año:
2015
Vol.:
66
N°:
20
Págs.:
6175 - 6189
Identification of early sulphur (S) deficiency indicators is important for species such as Brassica napus, an S-demanding crop in which yield and the nutritional quality of seeds are negatively affected by S deficiency. Because S is mostly stored as SO42- in leaf cell vacuoles and can be mobilized during S deficiency, this study investigated the impact of S deprivation on leaf osmotic potential in order to identify compensation processes. Plants were exposed for 28 days to S or to chlorine deprivation in order to differentiate osmotic and metabolic responses. While chlorine deprivation had no significant effects on growth, osmotic potential and nitrogen metabolism, Brassica napus revealed two response periods to S deprivation. The first one occurred during the first 13 days during which plant growth was maintained as a result of vacuolar SO42- mobilization. In the meantime, leaf osmotic potential of S-deprived plants remained similar to control plants despite a reduction in the SO42- osmotic contribution, which was fully compensated by an increase in NO3-, PO43- and Cl- accumulation. The second response occurred after 13 days of S deprivation with a significant reduction in growth, leaf osmotic potential, NO3- uptake and NO3- reductase activity, whereas amino acids and NO3- were accumulated. This kinetic analysis of S deprivation suggested that a ([Cl-]+[NO3-]+[PO43-]):[SO42-] ratio could provide a relevant indicator of S deficiency,
Revista:
JOURNAL OF MEDICINAL FOOD
ISSN:
1096-620X
Año:
2015
Vol.:
18
N°:
5
Págs.:
572 - 577
Humic acids (HAs) have a rather pleiotropic presence, however, their biological effects are still unclear. In this study, we focused on possible hepatoprotective effects of either HA alone or in combination with ß-glucan. Using a model of experimental hepatotoxicity caused by carbon tetrachloride (CCL4), we showed that both HA and the glucan-HA combination offered significant protection against hepatotoxicity, with the combination offering superior effects. Our biochemical observations were confirmed by histological evaluation. Based on the experimental data, we conclude that whereas HA has significant effects, the synergy with glucan offers superior effects.
Autores:
A.; S.; V; et al.
Revista:
FRONTIERS IN PLANT SCIENCE
ISSN:
1664-462X
Año:
2015
Vol.:
6
N°:
317
Higher plants have to cope with fluctuating mineral resource availability. However, strategies such as stimulation of root growth, increased transporter activities, and nutrient storage and remobilization have been mostly studied for only a few macronutrients. Leaves of cultivated crops (Zea mays, Brassica napus, Pisum sativum, Triticum aestivum, Hordeum vulgare) and tree species (Quercus robur, Populus nigra, Alnus glutinosa) grown under field conditions were harvested regularly during their life span and analyzed to evaluate the net mobilization of 13 nutrients during leaf senescence. While N was remobilized in all plant species with different efficiencies ranging from 40% (maize) to 90% (wheat), other macronutrients (K-P-S-Mg) were mobilized in most species. Ca and Mn, usually considered as having low phloem mobility were remobilized from leaves in wheat and barley. Leaf content of Cu-Mo-Ni-B-Fe-Zn decreased in some species, as a result of remobilization. Overall, wheat, barley and oak appeared to be the most efficient at remobilization while poplar and maize were the least efficient. Further experiments were performed with rapeseed plants subjected to individual nutrient deficiencies. Compared to field conditions, remobilization from leaves was similar (N-S-Cu) or increased by nutrient deficiency (K-P-Mg) while nutrient deficiency had no effect on Mo-Zn-B-Ca-Mn, which seemed to be non-mobile during leaf senescence under field conditions.
Autores:
I.; Aroca, R.; M.; et al.
Revista:
PHYSIOLOGIA PLANTARUM
ISSN:
0031-9317
Año:
2015
Vol.:
155
N°:
3
Págs.:
338 - 354
Although climate scenarios have predicted an increase in [CO2] and temperature conditions, to date few experiments have focused on the interaction of [CO2] and temperature effects in wheat development. Recent evidence suggests that photosynthetic acclimation is linked to the photorespiration and N assimilation inhibition of plants exposed to elevated CO2. The main goal of this study was to analyze the effect of interacting [CO2] and temperature on leaf photorespiration, C/N metabolism and N transport in wheat plants exposed to elevated [CO2] and temperature conditions. For this purpose, wheat plants were exposed to elevated [CO2] (400 vs 700 mu molmol(-1)) and temperature (ambient vs ambient+4 degrees C) in CO2 gradient greenhouses during the entire life cycle. Although at the agronomic level, elevated temperature had no effect on plant biomass, physiological analyses revealed that combined elevated [CO2] and temperature negatively affected photosynthetic performance. The limited energy levels resulting from the reduced respiratory and photorespiration rates of such plants were apparently inadequate to sustain nitrate reductase activity. Inhibited N assimilation was associated with a strong reduction in amino acid content, conditioned leaf soluble protein content and constrained leaf N status. Therefore, the plant response to elevated [CO2] and elevated temperature resulted in photosynthetic acclimation. The reduction in transpiration rates induced limitations in nutrient transport in leaves of plants exposed to elevated [CO2] and temperature, led to mineral depletion and therefore contributed to the inhibition of photosynthetic activity.
Revista:
PHYSIOLOGIA PLANTARUM
ISSN:
1399-3054
Año:
2015
Vol.:
155
N°:
3
Págs.:
338 - 354
Although climate scenarios have predicted an increase in [CO2] and temperature conditions, to date few experiments have focused on the interaction of [CO2] and temperature effects in wheat development. Recent evidence suggests that photosynthetic acclimation is linked to the photorespiration and N assimilation inhibition of plants exposed to elevated CO2. The main goal of this study was to analyze the effect of interacting [CO2] and temperature on leaf photorespiration, C/N metabolism and N transport in wheat plants exposed to elevated [CO2] and temperature conditions. For this purpose, wheat plants were exposed to elevated [CO2] (400 vs 700 mu molmol(-1)) and temperature (ambient vs ambient+4 degrees C) in CO2 gradient greenhouses during the entire life cycle. Although at the agronomic level, elevated temperature had no effect on plant biomass, physiological analyses revealed that combined elevated [CO2] and temperature negatively affected photosynthetic performance. The limited energy levels resulting from the reduced respiratory and photorespiration rates of such plants were apparently inadequate to sustain nitrate reductase activity. Inhibited N assimilation was associated with a strong reduction in amino acid content, conditioned leaf soluble protein content and constrained leaf N status. Therefore, the plant response to elevated [CO2] and elevated temperature resulted in photosynthetic acclimation. The reduction in transpiration rates induced limitations in nutrient ...
Autores:
Stamatiadis, S. (Autor de correspondencia); Evangelou, L.; Yvin, J. C.; et al.
Revista:
JOURNAL OF APPLIED PHYCOLOGY
ISSN:
0921-8971
Año:
2015
Vol.:
27
N°:
1
Págs.:
589 - 600
A greenhouse experiment was conducted to evaluate the effects of foliar application of an Ascophyllum nodosum seaweed extract (AZAL5) on the growth, nutrient uptake, and yield of winter wheat in a surface soil of the Thessaly Plain classified as TypicXerorthent. Twelve treatment combinations in a randomized complete block design with a factorial arrangement were composed of two rates of inorganic fertilizer (0 and 50 ppm N), three rates of AZAL5 (0, 1.5, and 3 % diluted extract), and two levels of water supply (75 and 45 % of field capacity). Under soil P and K sufficiency, the addition of fertilizer N greatly increased grain yield and nutrient uptake in the shoots (N and K) and grain (N, P, and K). Reduced water supply decreased grain yield and caused water stress as evidenced by decreased ¿13C in the N-deficient treatments and decreased nutrient uptake. AZAL5 application caused increased grain K uptake and a 25 % increase in yield only when mineral N was added. Differences in the efficacy of the two AZAL5 concentrations indicated that optimal dilution ratios were directly or indirectly dependent on soil water content. Complex interaction effects between AZAL5 and water supply on grain ¿13C could not be explained by conventional physiological response to water stress. The lack of biomass, nutrient content, and ¿13C differences between AZAL5 and control treatments in the shoot indicated that the reproductive organs of wheat were the main site of biostimulant action.
Revista:
PLANT PHYSIOLOGY AND BIOCHEMISTRY
ISSN:
0981-9428
Año:
2015
Vol.:
86
Págs.:
66 - 71
The importance of zinc (Zn) has been of little concern in human nutrition despite a strong decrease of this element in crops since the rise of high yielding varieties. For better food quality, Zn biofortification can be used, but will be optimal only if mechanisms governing Zn management are better known. Using Zn deficiency, we are able to demonstrate that Zn is not remobilized in Brassica napus (B. napus). Thus, remobilization processes should not be targeted by biofortification strategies. This study also complemented previous work by investigating leaf responses to Zn deficiency, especially from proteomic and ionomic points of view, showing for example, an increase in Manganese (Mn) content and of the Mn-dependent protein, Oxygen Evolving Enhancer.
Autores:
V.; A.; A.; et al.
Revista:
PLOS ONE
ISSN:
1932-6203
During the last 40 years, crop breeding has strongly increased yields but has had adverse effects on the content of micronutrients, such as Fe, Mg, Zn and Cu, in edible products despite their sufficient supply in most soils. This suggests that micronutrient remobilization to edible tissues has been negatively selected. As a consequence, the aim of this work was to quantify the remobilization of Cu in leaves of Brassica napus L. during Cu deficiency and to identify the main metabolic processes that were affected so that improvements can be achieved in the future. While Cu deficiency reduced oilseed rape growth by less than 19% compared to control plants, Cu content in old leaves decreased by 61.4%, thus demonstrating a remobilization process between leaves. Cu deficiency also triggered an increase in Cu transporter expression in roots (COPT2) and leaves (HMA1), and more surprisingly, the induction of the MOT1 gene encoding a molybdenum transporter associated with a strong increase in molybdenum (Mo) uptake. Proteomic analysis of leaves revealed 33 proteins differentially regulated by Cu deficiency, among which more than half were located in chloroplasts. Eleven differentially expressed proteins are known to require Cu for their synthesis and/or activity. Enzymes that were located directly upstream or downstream of Cu-dependent enzymes were also differentially expressed.
Autores:
Sánchez-Romera, B.; Ruiz-Lozano, J. M.; Li, G.; et al.
Revista:
PLANT CELL AND ENVIRONMENT
ISSN:
0140-7791
Año:
2014
Vol.:
37
N°:
4
Págs.:
995 - 1008
The role of jasmonic acid in the induction of stomatal closure is well known. However, its role in regulating root hydraulic conductivity (L) has not yet been explored. The objectives of the present research were to evaluate how JA regulates L and how calcium and abscisic acid (ABA) could be involved in such regulation. We found that exogenous methyl jasmonate (MeJA) increased L of Phaseolus vulgaris, Solanum lycopersicum and Arabidopsis thaliana roots. Tomato plants defective in JA biosynthesis had lower values of L than wild-type plants, and that L was restored by addition of MeJA. The increase of L by MeJA was accompanied by an increase of the phosphorylation state of the aquaporin PIP2. We observed that MeJA addition increased the concentration of cytosolic calcium and that calcium channel blockers inhibited the rise of L caused by MeJA. Treatment with fluoridone, an inhibitor of ABA biosynthesis, partially inhibited the increase of L caused by MeJA, and tomato plants defective in ABA biosynthesis increased their L after application of MeJA. It is concluded that JA enhances L and that this enhancement is linked to calcium and ABA dependent and independent signalling pathways.
Autores:
Pro, D.; Huguet, S.; Arkoun, M.; et al.
Revista:
CARBOHYDRATE POLYMERS
ISSN:
0144-8617
Año:
2014
Vol.:
112
Págs.:
145 - 151
N-Butyl-phosphorotriamide (NBPT) is a fertilizer widely used for its urease inhibiting properties. Nevertheless, formulations currently commercialized are complex and do not avoid severe decrease of activity due to the low stability of the bioactive compound under acidic conditions. According to its structure, NPBT was thought to be able to interact with both polar additives, by its phosphoramide function, and hydrophobic ones, through its alkyl chain. In this context, and in order to simplify formulations of this bioactive compound, a panel of natural polysaccharides was studied, including starch, ß-(1,3)-glucans, carraghenans and alginates. We also used cyclodextrins, characterized the most stable inclusion complex with ¿-cyclodextrin and evaluated the stability of NBPT thus protected against hydrolysis under acidic conditions.
Revista:
BMC PLANT BIOLOGY
ISSN:
1471-2229
Año:
2014
Vol.:
14
N°:
36
Págs.:
1 - 12
BACKGROUND: Plant growth-promoting rhizobacteria (PGPR) are naturally occurring soil bacteria which benefit plants by improving plant productivity and immunity. The mechanisms involved in these processes include the regulation of plant hormone levels such as ethylene and abscisic acid (ABA). The aim of the present study was to determine whether the activity of Bacillus megaterium PGPR is affected by the endogenous ABA content of the host plant. The ABA-deficient tomato mutants flacca and sitiens and their near-isogenic wild-type parental lines were used. Growth, stomatal conductance, shoot hormone concentration, competition assay for colonization of tomato root tips, and root expression of plant genes expected to be modulated by ABA and PGPR were examined.
RESULTS: Contrary to the wild-type plants in which PGPR stimulated growth rates, PGPR caused growth inhibition in ABA-deficient mutant plants. PGPR also triggered an over accumulation of ethylene in ABA-deficient plants which correlated with a higher expression of the pathogenesis-related gene Sl-PR1b.
CONCLUSIONS: Positive correlation between over-accumulation of ethylene and a higher expression of Sl-PR1b in ABA-deficient mutant plants could indicate that maintenance of normal plant endogenous ABA content may be essential for the growth promoting action of B. megaterium by keeping low levels of ethylene production.
Revista:
ADSORPTION-JOURNAL OF THE INTERNATIONAL ADSORPTION SOCIETY
ISSN:
0929-5607
Año:
2014
Vol.:
20
N°:
5 - 6
Págs.:
667 - 675
The effects of the humic acid (HA) nature and the activated carbon (AC) surface chemistry on the effectiveness of HA removal were investigated. Brown (BHA) and gray (GHA) humic acid fractions of different structure and physicochemical properties were tested in the adsorption process using mesoporous ACs. The modification of chemical structure and surface properties of AC was achieved by ammonization (AC/N) and hydrogen treatment (AC/H). Both approaches led to a decrease in the oxygen content followed by an increase in the carbon basicity, maintaining the porous texture of AC nearly unaltered. Over twice higher removal degree of BHA and GHA was observed for the modified ACs. The kinetics of adsorption of HA fractions have been discussed using the pseudo-second-order model and the intraparticle diffusion model. All ACs showed a higher adsorption capacity toward BHA compared to GHA, which is mainly attributed to the lower molecular weight of BHA. The shape of the equilibrium isotherms indicates a strong competition between water and HA molecules for adsorption sites of the carbon surface.
Revista:
JOURNAL OF PLANT GROWTH REGULATION
ISSN:
0721-7595
Año:
2014
Vol.:
33
N°:
2
Págs.:
430 - 439
Previous studies have reported that a purified sedimentary humic acid (PHA) was able to increase the concentration of nitric oxide (NO), indole-acetic acid (IAA) and ethylene in cucumber roots. Here, we investigated if these effects are functionally related to the ability of PHA to improve shoot growth. The effect of specific inhibitors of NO, IAA and ethylene functionality and signaling on PHA-induced shoot growth was studied. Likewise, the effect of these inhibitors on the synthesis and activity of the phytoregulators concerned by PHA action in cucumber roots was also explored. The results show that shoot growth promoted by PHA is due to an increase of IAA concentration in the root through both a NO-dependent and a NO-independent pathway. In addition, the increased ethylene production in the root is regulated by an IAA-dependent pathway. Finally, results also showed that the increase of ABA concentration in the root is regulated through both IAA- and ethylene-dependent pathways. In summary, the shoot growth promoting action of PHA involves a complex hormonal network. On one hand, the PHA action is functionally linked to increments in NO and IAA concentration in roots. And on the other hand, PHA action also increases ethylene and ABA root concentration mediated by NO-IAA dependent pathways.
Revista:
JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE
ISSN:
1436-8730
Año:
2014
Vol.:
177
Págs.:
128 - 136
The aim of this review is to describe the main physicochemical characteristics of diverse typesof humic-metal-phosphate acid complexes. The effects of these complexes on phosphorus (P)fixation in soils with different pH values and physicochemical features and on plant phosphorusuptake are also discussed. Humic-metal-phosphate complexes have apparent stability con-stants in the same range as those of metal-humic complexes, in solutions with diverse pH andionic-strength values. Likewise, the molecular-size distribution of humic-metal-phosphate com-plexes as a function of pH is similar to that of potassium or sodium humates and metal-humiccomplexes. Humic-metal-phosphate complexes are able to decrease phosphate fixation in soilsand increase plant growth and phosphate uptake. Phosphorus fertilizers containing humic-metal-phosphate complexes proved to be efficient to improve plant growth and P uptake withrespect to conventional fertilizers such as single superphosphate. The values of parametersrelated to plant phosphorus-utilization efficiency (PUt E) suggest that the regulation of rootacquisition of phosphate from these complexes could involve the interregulation of a system forthe optimization of metabolic P utilization in the shoot and another system involving stressresponses of roots under phosphorus deficiency.
Revista:
PHYSIOLOGIA PLANTARUM
ISSN:
0031-9317
Año:
2014
Vol.:
151
N°:
4
Págs.:
375 - 389
This study examines the extent to which the predicted CO2 -protective effects on the inhibition of growth, impairment of photosynthesis and nutrient imbalance caused by saline stress are mediated by an effective adaptation of the endogenous plant hormonal balance. Therefore, sweet pepper plants (Capsicum annuum, cv. Ciclón) were grown at ambient or elevated [CO2] (400 or 800 µmol mol(-1)) with a nutrient solution containing 0 or 80 mM NaCl. The results show that, under saline conditions, elevated [CO2] increased plant dry weight, leaf area, leaf relative water content and net photosynthesis compared with ambient [CO2], whilst the maximum potential quantum efficiency of photosystem II was not modified. In salt-stressed plants, elevated [CO2 ] increased leaf NO3(-) concentration and reduced Cl(-) concentration. Salinity stress induced ABA accumulation in the leaves but it was reduced in the roots at high [CO2], being correlated with the stomatal response. Under non-stressed conditions, IAA was dramatically reduced in the roots when high [CO2] was applied, which resulted in greater root DW and root respiration. Additionally, the observed high CK concentration in the roots (especially tZR) could prevent downregulation of photosynthesis at high [CO2], as the N level in the leaves was increased compared with the ambient [CO2], under salt-stress conditions. These results demonstrate that the hormonal balance was altered by the [CO2], which resulted in significant changes at the grow
Revista:
PLANT AND CELL PHYSIOLOGY
ISSN:
0032-0781
Año:
2014
Vol.:
55
N°:
5
Págs.:
1017 - 1029
It is known that the presence of arbuscular mycorrhizal fungi within the plant roots enhances the tolerance of the host plant to different environmental stresses, although the positive effect of the fungi in plants under waterlogged conditions has not been well studied. Tolerance of plants to flooding can be achieved through different molecular, physiological and anatomical adaptations, which will affect their water uptake capacity and therefore their root hydraulic properties. Here, we investigated the root hydraulic properties under non-flooded and flooded conditions in non-mycorrhizal tomato plants and plants inoculated with the arbuscular mycorrhizal fungus Rhizophagus irregularis. Only flooded mycorrhizal plants increased their root hydraulic conductivity, and this effect was correlated with a higher expression of the plant aquaporin SlPIP1;7 and the fungal aquaporin GintAQP1. There was also a higher abundance of the PIP2 protein phoshorylated at Ser280 in mycorrhizal flooded plants. The role of plant hormones (ethylene, ABA and IAA) in root hydraulic properties was also taken into consideration, and it was concluded that, in mycorrhizal flooded plants, ethylene has a secondary role regulating root hydraulic conductivity whereas IAA may be the key hormone that allows the enhancement of root hydraulic conductivity in mycorrhizal plants under low oxygen conditions.
Autores:
V.; P.; L.; et al.
Revista:
JOURNAL OF PLANT GROWTH REGULATION
ISSN:
0721-7595
Año:
2014
Vol.:
33
N°:
2
Págs.:
305 - 316
Different strategies, known as crop biofortification, can be used to increase micronutrient concentrations in harvested parts to reduce nutrient deficiencies in the human diet. Apart from fertilization and genetic selection, a more environmentally friendly, less expensive, and more immediate solution could rely on the use of biostimulants derived from natural materials. Two biostimulants, AZAL5 and HA7, which are derived from seaweed and black peat, respectively, have been previously described as promoting growth of Brassica napus and having a substantial effect on gene expression. They were further studied to evaluate their effects on N and S and a wide range of other nutrients (that is, K, Ca, P, Mg, Fe, Na, Mn, B, Si, Cu, and Zn). Providing these two biostimulants in the nutrient solution did not change the mineral supply significantly, but they mostly stimulated root growth and macronutrient uptake (N, S, K, and P) at a level similar to growth. Both biostimulants also stimulate chloroplast division. More surprisingly, they also increased Mg, Mn, Na, and Cu plant concentrations and root-to-shoot translocation of Fe and Zn. These observations were associated with an increased expression of a Cu transporter (COPT2) and NRAMP3, a gene putatively involved in Fe and Zn translocation. Overall, this study showed that specific nutrient balance and transport were stimulated by both biostimulants more significantly than growth, offering new perspectives for biofortification strateg.
Autores:
Arkoun, M.; Jannin, L.; Laîné, P.; et al.
Revista:
PLANT AND SOIL
ISSN:
0032-079X
Año:
2013
Vol.:
362
N°:
1 - 2
Págs.:
79 - 92
Background and aims: Urea is the major nitrogen (N) form supplied as fertilizer in agriculture. However, urease, a nickel-dependent enzyme, allows plants to use external or internally generated urea as a nitrogen source. Since a urease inhibitor is frequently applied in conjunction with urea fertilizer, the N-metabolism of plants may be affected. The aim of this study was to determine physiological and molecular effects of nickel deficiency and a urease inhibitor on urea uptake and assimilation in oilseed rape.
Methods: Plants were grown on hydroponic solution with urea as the sole N source under three treatments: plants treated with nickel (+Ni) as a control, without nickel (¿Ni) and with nickel and phenylphosphorodiamidate (+Ni+PPD). Urea transport and assimilation were investigated.
Results: The results show that Ni-deficiency or PPD supply led to reduced growth and reduced 15N-uptake from urea. This effect was more pronounced in PPD-treated plants, which accumulated high amounts of urea and ammonium. Thus, Ni-deficiency or addition of PPD, limit the availability of N and decreased shoot and root amino acid content. The up-regulation of BnDUR3 in roots indicated that this gene is a component of the stress response to nitrogen-deficiency. A general decline of glutamine synthetase (GS) activity and activation of glutamate dehydrogenase (GDH) and increases in its expression level were observed in control plants.
Revista:
JOURNAL OF PLANT PHYSIOLOGY
ISSN:
0176-1617
Año:
2013
Vol.:
170
N°:
1
Págs.:
47 - 55
Arbuscular mycorrhizal (AM) symbiosis can alleviate salt stress in plants. However the intimate mechanisms involved, as well as the effect of salinity on the production of signalling molecules associated to the host plant-AM fungus interaction remains largely unknown. In the present work, we have investigated the effects of salinity on lettuce plant performance and production of strigolactones, and assessed its influence on mycorrhizal root colonization. Three different salt concentrations were applied to mycorrhizal and non-mycorrhizal plants, and their effects, overtime, analyzed. Plant biomass, stomatal conductance, efficiency of photosystem II, as well as ABA content and strigolactone production were assessed. The expression of ABA biosynthesis genes was also analyzed.
AM plants showed improved growth rates and a better performance of physiological parameters such as stomatal conductance and efficiency of photosystem II than non-mycorrhizal plants under salt stress since very early stages - 3 weeks - of plant colonization. Moreover, ABA levels were lower in those plants, suggesting that they were less stressed than non-colonized plants. On the other hand, we show that both AM symbiosis and salinity influence strigolactone production, although in a different way in AM and non-AM plants. The results suggest that AM symbiosis alleviates salt stress by altering the hormonal. profiles and affecting plant physiology in the host plant.
Autores:
Jannin, L.; Arkoun, M.; Etienne, P.; et al.
Revista:
JOURNAL OF PLANT GROWTH REGULATION
ISSN:
0721-7595
Año:
2013
Vol.:
32
N°:
1
Págs.:
31 - 52
Despite its high capacity to take up nitrate from soil, winter rapeseed (Brassica napus) is characterized by a low N recovery in seeds. Thus, to maintain yield, rapeseed requires a high fertilization rate. Increasing nutrient use efficiency in rapeseed by addition of a biostimulant could help improve its agroenvironmental balance. The effects of marine brown seaweed Ascophyllum nodosum on plant growth have been well described physiologically. However, to our knowledge, no study has focused on transcriptomic analyses to determine metabolic targets of these extracts. A preliminary screening of different extracts revealed a significant effect of one of them (AZAL5) on rapeseed root (+102 %) and shoot (+23 %) growth. Microarray analysis was then used on AZAL5-treated or nontreated plants to characterize changes in gene expression that were further supported by physiological evidence. Stimulation of nitrogen uptake (+21 and +115 % in shoots and roots, respectively) and assimilation was increased in a similar manner to growth, whereas sulfate content (+63 and +133 % in shoots and roots, respectively) was more strongly stimulated leading to sulfate accumulation. Among the identified genes whose expression was affected by AZAL5, MinE, a plastid division regulator, was the most strongly affected. Its effect was supported by microscopic analysis showing an enhancement of chloroplast number per cell and starch content but without a significant difference in net photosynthetic rate.
Revista:
PHYSIOLOGIA PLANTARUM
ISSN:
0031-9317
Año:
2013
Vol.:
148
N°:
4
Págs.:
522 - 537
An understanding of the mechanisms underlying ammonium (NH4+) toxicity in plants requires prior knowledge of the metabolic uses for nitrogen (N) and carbon (C). We have recently shown that pea plants grown at high NH4+ concentrations suffer an energy deficiency associated with a disruption of ionic homeostasis. Furthermore, these plants are unable to adequately regulate internal NH4+ levels and the cell-charge balance associated with cation uptake. Herein we show a role for an extra-C application in the regulation of C¿N metabolism in NH4+-fed plants. Thus, pea plants (Pisum sativum) were grown at a range of NH4+ concentrations as sole N source, and two light intensities were applied to vary the C supply to the plants. Control plants grown at high NH4+ concentration triggered a toxicity response with the characteristic pattern of C-starvation conditions. This toxicity response resulted in the redistribution of N from amino acids, mostly asparagine, and lower C/N ratios. The C/N imbalance at high NH4+ concentration under control conditions induced a strong activation of root C metabolism and the upregulation of anaplerotic enzymes to provide C intermediates for the tricarboxylic acid cycle. A high light intensity partially reverted these C-starvation symptoms by providing higher C availability to the plants. The extra-C contributed to a lower C4/C5 amino acid ratio while maintaining the relative contents of some minor amino acids involved in key pathways regulating the C/N sta
Revista:
BIOLOGY AND FERTILITY OF SOILS
ISSN:
0178-2762
Año:
2013
Vol.:
49
N°:
4
Págs.:
395 - 401
Organic complexed super-phosphates (CSPs) are formed by the complexation of humic acid (HA) with calcium monophosphate. The aim of this study was to determine whether two CSPs, characterized by different HA concentrations, added to a calcareous soil at an agronomic dose, were able to maintain the phosphorus (P) in a soluble form longer than the superphosphate fertilizer. Another important goal was to verify if CSP could positively influence soil microbial biomass and soil microbiological activities. Organic complexed super-phosphates were capable of keeping a large portion of P in a soluble form under different soil water conditions. In particular, the CSP with the highest organic C content was the most effective product, capable of maintaining, in an available form, the 73 % of the initially added P at the end of the experiment. In addition, it was the most effective in increasing C¿CO2 soil emission, microbial biomass carbon (C) and nitrogen (N), fluoresceine diacetate hydrolysis and activities of alkaline phosphomonoesterase, ß-glucosidase and urease. The addition of CSPs to soil probably produced a priming effect, increasing several times C¿CO2 release by the treated soil. The significant correlation (p¿<¿0.05) between C¿CO2 emission and the amount of C added to soil by CSP suggests that the added HA acted as trigger molecules.
Revista:
PLANT SCIENCE
ISSN:
0168-9452
Año:
2013
Vol.:
198
Págs.:
39 - 45
Numerous studies have investigated the molecular and physiological-morphological mechanisms induced in plant roots in response to specific nutrient deficiencies. Both transcriptional and post-transcriptional mechanisms are involved that increase root uptake under nutrient deficiency. Root nutrient deficiency-stress root responses are mainly regulated by the nutrient status in the shoot. The signals involved in shoot to root cross-talk regulation processes for the activation of nutrient-deficiency induced root responses are not clearly elucidated. The physiological-molecular events in the leaf linked to the nutrient availability for metabolic use, are also poorly known. In this context, we focus our attention on iron plant nutrition. Some experimental evidence suggests the existence of a regulatory system concerned with the optimization of the metabolic use of iron, mainly under conditions of iron starvation. This system seems to be activated by the deficiency in iron-availability for metabolic processes in the leaf and regulates the activation of some iron-stress root responses. This regulation seems to be probably expressed by affecting the production and/or translocation of the activating signal sent from the shoot to the root under conditions of iron deficiency in the shoot.
Autores:
Sudre, D.; Gutierrez-Carbonell, E.; Lattanzio, G.; et al.
Revista:
JOURNAL OF EXPERIMENTAL BOTANY
ISSN:
0022-0957
Año:
2013
Vol.:
64
N°:
10
Págs.:
2665 - 2668
Iron homeostasis is an important process for flower development and plant fertility. The role of plastids in these processes has been shown to be essential. To document the relationships between plastid iron homeostasis and flower biology further, a global study (transcriptome, proteome, metabolome, and hormone analysis) was performed of Arabidopsis flowers from wild-type and triple atfer1-3-4 ferritin mutant plants grown under iron-sufficient or excess conditions. Some major modifications in specific functional categories were consistently observed at these three omic levels, although no significant overlaps of specific transcripts and proteins were detected. These modifications concerned redox reactions and oxidative stress, as well as amino acid and protein catabolism, this latter point being exemplified by an almost 10-fold increase in urea concentration of atfer1-3-4 flowers from plants grown under iron excess conditions. The mutant background caused alterations in Fe-haem redox proteins located in membranes and in hormone-responsive proteins. Specific effects of excess Fe in the mutant included further changes in these categories, supporting the idea that the mutant is facing a more intense Fe/redox stress than the wild type. The mutation and/or excess Fe had a strong impact at the membrane level, as denoted by the changes in the transporter and lipid metabolism categories.
Revista:
JOURNAL OF GEOCHEMICAL EXPLORATION
ISSN:
0375-6742
Año:
2013
Vol.:
129
Págs.:
14 - 17
The main objective of this study is to investigate the more relevant binding sites (functional groups) involved in the complexation of Fe(III) and Cu(II) by humic-based structures. To this aim we have generated a set of seven humic-based samples (MHA) by the application of a hemi-synthetic process consisting in the oxidative polymerization of different combinations of three sources of natural organic molecules: two humic acids obtained from peat and leonardite, and natural tannin extracted from the quebracho tree (Schinopsis sp.) bark. These MHA were extensively characterized by using complementary analytical techniques (13C NMR, size-exclusion chromatography, electron paramagnetic resonance, and total phenol-reductant content), and their ability to complex Fe(III) and Cu(II) was also calculated by fluorescence quenching method. The data were studied by using general correlation matrix and principal component analysis.
The results obtained, taken together, indicated that in a set of humic-based structures presenting carboxylic, phenol and O-alkyl groups, and diverse aliphatic/aromatic character, the complexation of Fe(III) mainly involved specific structural arrangements including carboxylic groups distributed in aliphatic domains. However, Cu(II) complexation involved singular structural arrangements including phenols (and probably substituted phenols) and O-alkyl groups in side chains of aromatic domains.
Revista:
CHEMSUSCHEM
ISSN:
1864-5631
Año:
2013
Vol.:
6
N°:
7
Págs.:
1245 - 1251
Fertilizers based on phosphate-metal-humate complexes are a new family of compounds that represents a more sustainable and bioavailable phosphorus source. The characterization of this type of complex by using solid (31)P NMR in several fertilizers, based on single superphosphate (SSP) and triple superphosphate (TSP) matrices, yielded surprising and unexpected trends in the intensity and fine structure of the (31)P NMR peaks. Computational chemistry methods allowed the characterization of phosphate-calcium-humate complexes in both SSP and TSP matrices, but also predicted the formation of a stable sulfate-calcium-humate complex in the SSP fertilizers, which has not been described previously. The stability of this complex has been confirmed by using ultrafiltration techniques. Preference towards the humic substance for the sulfate-metal phase in SSP allowed the explanation of the opposing trends that were observed in the experimental (31)P NMR spectra of SSP and TSP samples. Additionally, computational chemistry has provided an assignment of the (31)P NMR signals to different phosphate ligands as well as valuable information about the relative strength of the phosphate-calcium interactions within the crystals.
Autores:
Vetvicka, V. (Autor de correspondencia); Vashishta, A.; Fuentes, M; et al.
Revista:
JOURNAL OF MEDICINAL FOOD
ISSN:
1096-620X
Año:
2013
Vol.:
16
N°:
7
Págs.:
625 - 632
Despite the rather common presence of humic acid (HA), our full knowledge of its biological effect is still lacking. In this article, we first performed a physicochemical characterization of several HAs, and next, we evaluated their ability to affect interleukin-2 secretion, antibody secretion, wound healing (an in vitro model using HaCaT cells), cancer growth (the Lewis lung carcinoma model), and protection against hepatotoxicity. In all tested reactions, HA showed significant stimulation on immune reactions, including suppression of cancer growth and inhibition of lipopolysaccharide-induced hepatotoxicity. These effects were dependent on its chemical properties. The pleiotropic effects of HA observed in this article suggest the possible role of these compounds in human nutrition.
Revista:
JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE
ISSN:
0022-5142
Año:
2013
Vol.:
93
N°:
2
Págs.:
293 - 303
BACKGROUND:
Previous studies showed that phosphate can be complexed by humic acids (HA) through stable metal (M) bridges (PMHA). We studied the thermodynamic properties of PMHA and their relationships with the ability of PMHA to both decrease soil P fixation and increase P availability for plants. With this aim, we studied the theoretical stability of PFeHA, PAlHA and PCaHA by molecular modelling methods in relation to the degree and intensity of P absorption in soils and the ability of plants to take up complexed P.
RESULTS:
A density functional theory (DFT) quantum chemical study enabled us to obtain stable structures for the three PMHA complexes in water solution. The theoretical stabilities (¿G¿) were consistent with that for apparent stability obtained by Scatchard method, PFeHA ¿ PAlHA > PCaHA, though the differences were clearer by the DFT method. Also the reduction of soil P fixation and the release of P from PMHA in the presence of an anionic resin confirmed the stability order of the different PMHA. Plant studies confirmed the ability of diverse plant species to take up both P and metal complexed in PMHA.
CONCLUSION:
The results indicated the potential efficiency of PMHA-based fertilizers to optimize P fertilization for crops cultivated in soils with high P fixation ability.
Revista:
JOURNAL OF RESIDUALS SCIENCE AND TECHNOLOGY
ISSN:
1544-8053
Año:
2012
Vol.:
9
N°:
1
Págs.:
1 - 7
Dry anaerobic digestion systems work with wastes that have a dry matter content above 20%. This technology has been used above all to treat the organic fraction of municipal solid waste making its application to the agro-food industry waste a novel approach. Co-digestion of vegetable and MBM by means of a batch system shows a good efficiency in spite of the presence of certain compounds at inhibitory levels (N-NH3 and VFA) which are detected in the process leachate.
Autores:
Fuentes, M; Fortuno, M.; Perez-Sarmiento, F.; et al.
Revista:
JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE
ISSN:
0022-5142
Año:
2012
Vol.:
92
N°:
15
Págs.:
3065 - 3071
BACKGROUND: Iron (Fe) chlorosis is a serious problem affecting the yield and quality of numerous crops and fruit trees cultivated in alkaline/calcareous soils. This paper describes the efficiency of a new class of natural hetero-ligand Fe(III) chelates (Fe-NHL) to provide available Fe for chlorotic lemon trees grown in alkaline/calcareous soils. These chelates involve the participation in the reaction system of a partially humified lignin-based natural polymer and citric acid. RESULTS: First results showed that Fe-NHL was adsorbed on the soil matrix while maintaining available Fe for plants in alkaline/calcareous solution. The effects of using three different sources as Fe fertilisers were also compared: two Fe-NHL formulations (NHL1, containing 100% of Fe as Fe-NHL, and NHL2, containing 80% of Fe as Fe-NHL and 20% of Fe as Fe-ethylenediamine-N,N'-bis-(o-hydroxyphenylacetic) acid (Fe-EDDHA)) and Fe-EDDHA. Both Fe-NHL formulations increased fruit yield without negative effects on fruit quality in comparison with Fe-EDDHA. In the absence of the Fe-starter fraction (NHL1), trees seemed to optimise Fe assimilation and translocation from Fe-NHL, directing it to those parts of the plant more involved in development. CONCLUSION: The field assays confirmed that Fe-NHL-based fertilisers are able to provide Fe to chlorotic trees, with results comparable to Fe-EDDHA. Besides, this would imply a more sustainable and less expensive remediation than synthetic chelates. Copyright (c) 2012 Society of Chemical Industry
Autores:
Arkoun, M. (Autor de correspondencia); Sarda, X.; Jannin, L.; et al.
Revista:
JOURNAL OF EXPERIMENTAL BOTANY
ISSN:
0022-0957
Año:
2012
Vol.:
63
N°:
14
Págs.:
5245 - 5258
N-fertilizer use efficiencies are affected by their chemical composition and suffer from potential N-losses by volatilization. In a field lysimeter experiment, (15)N-labelled fertilizers were used to follow N uptake by Brassica napus L. and assess N-losses by volatilization. Use of urea with NBPT (urease inhibitor) showed the best efficiency with the lowest N losses (8% of N applied compared with 25% with urea alone). Plants receiving ammonium sulphate, had similar yield achieved through a better N mobilization from vegetative tissues to the seeds, despite a lower N uptake resulting from a higher volatilization (43% of applied N). Amounts of (15)N in the plant were also higher when plants were fertilized with ammonium nitrate but N-losses reached 23% of applied N. In parallel, hydroponic experiments showed a deleterious effect of ammonium and urea on the growth of oilseed rape. This was alleviated by the nitrate supply, which was preferentially taken up. B. napus was also characterized by a very low potential for urea uptake. BnDUR3 and BnAMT1, encoding urea and ammonium transporters, were up-regulated by urea, suggesting that urea-grown plants suffered from nitrogen deficiency. The results also suggested a role for nitrate as a signal for the expression of BnDUR3, in addition to its role as a major nutrient. Overall, the results of the hydroponic study showed that urea itself does not contribute significantly to the N nutrition of oilseed rape.
Revista:
AGROCIENCIA (MEXICO)
ISSN:
1405-3195
Año:
2012
Vol.:
16
N°:
3
Págs.:
188 - 190
A number of studies have shown the ability of natural organic matter (NOM) in general and humic substances (HS) in particular, to affect the development of plants and microorganisms in many different natural ecosystems and agroecosystems. Regarding plants, these NOM and HS effects were expressed in both root growth and architecture, and shoot growth. However, these effects were different in intensity and quality depending on several intrinsic and extrinsic factors associated with HS structure and concentration, plant species and soil properties. Two main mechanisms have been proposed to explain the beneficial action of NOM and HS on plant growth. An indirect effect expressed through the improvement of plant nutrition by increasing soil nutrient availability, principally some micronutrients (mostly P and Fe); and a possible direct action affecting the transcriptional and post-transcriptional regulation of several enzymes and molecular transporters in the root. These biological effects within the plant seem to be associated with both nutrient root uptake ability and the efficient use of the nutrient in plant leaves. In this communication, the relationships between the effects of HS on root development, shoot development, plant nutrition, and soil properties; are discussed. This study is developed in the context of the links existing between the signal role of some nutrients and the hormonal balance in both root and shoot.
Autores:
Jannin, L. (Autor de correspondencia); Arkoun, M.; Ourry, A.; et al.
Revista:
PLANT AND SOIL
ISSN:
0032-079X
Año:
2012
Vol.:
359
N°:
1 - 2
Págs.:
297 - 319
Background & aims: Winter rapeseed (Brassica napus) is characterized by a low N recovery in seeds and requires high rates of fertilization to maintain yield. Its nutrient use efficiency could be improved by addition of a biostimulant such as humic acids whose physiological effects have been described previously in some plant species. However, to our knowledge, no study has focused on transcriptomic analyses to determine metabolic targets of this extract.
Methods: A preliminary screening of ten humic acids revealed a significant effect of one of them (HA7) on rapeseed root growth. Microarray analysis was then used on HA7-treated or non-treated plants to characterize changes in gene expression that were further supported by physiological evidence.
Results: Stimulation of nitrogen uptake (+15% in shoots and +108% in roots) and assimilation was found to be increased in a similar manner to growth while sulfate content (+76% in shoots and +137% in roots) was more strongly stimulated leading to higher sulfate accumulation. In parallel, microscopic analysis showed an enhancement of chloroplast number per cell.
Conclusion: It is therefore suggested that HA7, which promotes plant growth and nutrient uptake, could be used as a supplementary tool to improve rapeseed nitrogen use efficiency.
Revista:
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
ISSN:
0021-8561
Año:
2012
Vol.:
60
N°:
8
Págs.:
2008 - 2017
A new type of superphosphate (organic complexed superphosphate (CSP)) has been developed by the introduction of organic chelating agents, preferably a humic acid (HA), into the chemical reaction of single superphosphate (SSP) production. This modification yielded a product containing monocalcium phosphate complexed by the chelating organic agent through Ca bridges. Theoretically, the presence of these monocalcium-phosphate-humic complexes (MPHC) inhibits phosphate fixation in soil, thus increasing P fertilizer efficiency. This study investigateed the structural and functional features of CSP fertilizers produced employing diverse HA with different structural features. To this end were used complementary analytical techniques: solid-phase 31P NMR, 13C NMR, laser-confocal microscopy, X-ray diffraction, and molecular modeling. Finally, the agronomical efficiency of four CSP have been compared with that of SSP as P sources for wheat plants grown in both alkaline and acidic soils in greenhouse pot trials under controlled conditions. The results obtained from the diverse analytical studies showed the formation of MPHC in CSP. Plant¿soil studies showed that CSP products were more efficient than SSP in providing available phosphate for wheat plants cultivated in various soils with different physicochemical features. This fact is probably associated with the ability of CSP complexes to inhibit phosphate fixation in soil.
Revista:
ENVIRONMENTAL AND EXPERIMENTAL BOTANY
ISSN:
0098-8472
Año:
2012
Vol.:
76
Págs.:
24 - 32
The increase in root growth is one of the major effects of humic substances, but the mechanisms involved in humic acid-mediated changes in root growth, morphology and architecture are poorly known. Probably, humic substances may act on plant development through an action on the hormonal balance within the plant, either directly or indirectly by affecting the root uptake of some nutrients. In this study we investigate in cucumber plants the effects of a purified sedimentary humic acid (PHA), without detectable concentrations of the main phytoregulators in its structure, on root architecture, and its relationships with the functional action of three phytoregulators, indole-acetic acid, ethylene and nitric oxide, which are also affected by the root application of this humic acid. The results obtained using inhibitors of auxin transport or action, inhibitors of ethylene biosynthesis or action, and a scavenger of nitric oxide indicate that the increase in the root concentration of these phytoregulators caused by the root application of PHA does not play an essential role in the expression of the main changes on root architecture caused by PHA in developed cucumber plants. Other factors, which could act in coordination or independently of those phytoregulators affected by PHA root application, must be involved in the whole action on this humic acid on root architecture in cucumber.
Revista:
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
ISSN:
0021-8561
Año:
2011
Vol.:
59
N°:
5
Págs.:
1900 - 1908
Hydroponic plant experiments demonstrated the efficiency of a type of humic acid-based water-insoluble phosphate fertilizers, named rhizosphere controlled fertilizers (RCF), to supply available phosphorus (P) to different plant species. This effect was well correlated to the root release of specific organic acids. In this context, the aims of this study are (i) to study the chemical nature of RCF using solid-state 31P NMR and (ii) to evaluate the real efficiency of RCF matrix as a source of P for wheat plants cultivated in an alkaline and acid soil in comparison with traditional water-soluble (simple superphosphate, SSP) and water-insoluble (dicalcium phosphate, DCP) P fertilizers. The 31P NMR study revealed the formation of multimetal (double and triple, MgZn and/or MgZnCa) phosphates associated with chelating groups of the humic acid through the formation of metal bridges. With regard to P fertilizer efficiency, the results obtained show that the RCF matrix produced higher plant yields than SSP in both types of soil, with DCP and the water-insoluble fraction from the RCF matrix (WI) exhibiting the best results in the alkaline soil. By contrast, in the acid soil, DCP showed very low efficiency, WI performed on a par with SSP, and RCF exhibited the highest efficiency, thus suggesting a protector effect of humic acid from soil fixation.
Revista:
PHARMACEUTICAL BIOLOGY
ISSN:
1388-0209
Año:
2011
Vol.:
49
N°:
6
Págs.:
620 - 626
Context: Stem and leaves infusion of Chuquiraga spinosa (R&P) Don. (Asteraceae) is used in the Peruvian traditional medicine for its anti-inflammatory properties and for the treatment of vaginal infections.
Objective: This study evaluated the antioxidant, anti-inflammatory and antifungal activities of C. spinosa for the first time.
Materials and methods: Extracts of methanol, 50% methanol and water were obtained from C. spinosa aerial parts. Antioxidant activity of the extracts was evaluated (DPPH center dot E (TM), ABTS center dot E (TM)<SU++</SU and superoxide radical-scavenging activity). The correlation between these results and total polyphenolic content was determined by Pearson''s Correlation Coefficient. Anti-inflammatory activity of 50% methanol extract was evaluated with the rat model of carrageenan-induced acute inflammation and mouse model of TPA-induced acute inflammation. The antifungal activity of the extracts against Cladosporium cucumerinum and Candida albicans was studied by direct bioautography, and antifungal activity against phytopathogenic fungi was performed by culture in potato dextrose agar plates.
Results: All the extracts showed high antioxidant activity, and there was correlation between the activity and total polyphenolic compounds. As 50% methanol extract was administered orally, the paw edema in rats was reduced significantly (52.5%). This extract, by topical administration, produced a reduction of 88.07% of the edema TPA-induced in ear of mice. The aqueous and 50% methanol extracts were active against C. albicans (minimum inhibitory concentration of 2.5 and 6.25 mu A mu g, respectively). The aqueous extract showed antifungal activity against C. cucumerinum (MIC: 2.5 mu A mu g).
Discussion and conclusion: Preliminary phytochemical screening and the analysis of the three extracts by high-performance liquid chromatography diode-array detection showed the majority compounds are flavonoids and phenolic acid derivatives. These compounds may be responsible of the radical-scavenging activity of these extracts as well as responsible of anti-inflammatory effect in vivo of 50% methanol extract. Several authors have demonstrated the antioxidant and anti-inflammatory properties of some flavonoids and phenolic acids. The antifungal activity of the extracts obtained from aerial parts of C. spinosa has been investigated here for the first time. Other studies are necessary to determine the mechanism of action and to identify the bioactive compounds of this plant.
Revista:
PLANT PHYSIOLOGY AND BIOCHEMISTRY
ISSN:
0981-9428
Año:
2011
Vol.:
49
N°:
5
Págs.:
545 - 556
The aim of this study was to investigate the effects of IAA and ABA in the shoot-to-root regulation of the expression of the main Fe-stress physiological root responses in cucumber plants subjected to shoot Fe functional deficiency. Changes in the expression of the genes CsFRO1, CsIRT1, CsHA1 and CsHA2 (coding for Fe(III)-chelate reductase (FCR), the Fe(II) transporter and H+-ATPase, respectively) and in the enzyme activity of FCR and the acidification capacity were measured. We studied first the ability of exogenous applications of IAA and ABA to induce these Fe-stress root responses in plants grown in Fe-sufficient conditions. The results showed that IAA was able to activate these responses at the transcriptional and functional levels, whereas the results with ABA were less conclusive. Thereafter, we explored the role of IAA in plants with or without shoot Fe functional deficiency in the presence of two types of IAA inhibitors, affecting either IAA polar transport (TIBA) or IAA functionality (PCIB). The results showed that IAA is involved in the regulation at the transcriptional and functional levels of both Fe root acquisition (FCR, Fe(II) transport) and rhizosphere acidification (H+-ATPase), although through different, and probably complementary, mechanisms. These results suggest that IAA is involved in the shoot-to-root regulation of the expression of Fe-stress physiological root responses.
Revista:
PLANT GROWTH REGULATION
ISSN:
0167-6903
Año:
2011
Vol.:
63
N°:
1
Págs.:
73 - 79
The use of urea as an N fertilizer has increased to such an extent that it is now the most widely used fertilizer in the world. However, N losses as a result of ammonia volatilization lead to a decrease in its efficiency, therefore different methods have been developed over the years to reduce these losses. One of the most recent involves the use of urea combined with urease inhibitors, such as N-(n-butyl) thiophosphoric triamide (NBPT), in an attempt to delay the hydrolysis of urea in the soil. The aim of this study was to perform an in-depth analysis of the effect that NBPT use has on plant growth and N metabolism. Wheat plants were cultivated in a greenhouse experiment lasting 4 weeks and fertilized with urea and NBPT at different concentrations (0, 0.012, 0.062, 0.125%). Each treatment was replicated six times. A non-fertilized control was also cultivated. Several parameters related with N metabolism were analysed at the end of growth period. NBPT use was found to have visible effects, such as a transitory yellowing of the leaf tips, at the end of the first week of treatment. At a metabolic level, plants treated with the inhibitor were found to have more urea in their tissues and a lower amino acid content, lower glutamine synthetase activity, and lower urease and glutamine synthetase content at the end of the study period, whereas their urease activity seemed to have recovered by this stage.
Revista:
JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE
ISSN:
0022-5142
Año:
2011
Vol.:
91
N°:
9
Págs.:
1569 - 1575
BACKGROUND: Some authors suggest that the absence of tillage in agricultural soils might have an influence on the efficiency of nitrogen applied in the soil surface. In this study we investigate the influence of no-tillage and soil characteristics on the efficiency of a urease inhibitor (N-(nbutyl)thiophosphoric triamide, NBPT) and a nitrification inhibitor (diciandiamide, DCD) in decreasing ammonia volatilization from urea and ammonium nitrate (AN), respectively.
RESULTS: The results indicate that ammonia volatilization in soils amended with urea was significantly higher than in those fertilized with AN. Likewise, the main soil factors affecting ammonia volatilization from urea are clay and sand soil contents. While clay impedes ammonia volatilization, sand favours it. The presence of organic residues on soil surface (no¿tillage) tends to increase ammonia volatilization from urea, although this fact depended on soil type. The presence of NBPT in urea fertilizer significantly reduced soil ammonia volatilization. This action of NBPT was negatively affected by acid soil pH and favoured by soil clay content.
CONCLUSION: The presence of organic residues on soil surface amended with urea increased ammonia volatilization, and was particularly high in sandy compared with clay soils. Application of NBPT reduced ammonia volatilization although its efficiency is reduced in acid soils. Concerning AN fertilization, there were no differences in ammonia volatilization with or without DCD
Revista:
JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE
ISSN:
1436-8730
Año:
2011
Vol.:
174
N°:
6
Págs.:
916 - 924
A greenhouse experiment was conducted to evaluate the effects of humic substances extracted from composted sewage sludge on growth, phenological development, and photosynthetic activity of pepper (Capsicum annuum L. cv. Piquillo) plants. Humic substances derived from composted sludge (HSS) were compared with those derived from leonardite (HSL). Two doses of both humic substances were assayed (200 and 500 mg C [L substrate](-1)) and compared with a control (C). HSS showed higher nitrogen content and a higher percentage of aliphatic carbon, as well as a lower content of aromatic and phenolic carbon than HSL. HSS significantly increased plant dry-matter production (up to 560%), plant height (86%151%), and leaf area (436%-1397%) during the early stages of pepper development. Net photosynthesis and stomatal conductance increased in the treatments with HSS (up to 48% and 63%, respectively) at the vegetative stage. In addition, HSS accelerated the phenological development of pepper plants, reducing significantly the number of days to flowering and ripening, which occurred 12 and 14 d earlier than in control plants, respectively. In general, the treatments with HSS and HSL did not markedly affect chlorophyll and nutrient concentrations in the leaves. At maturity, only small differences in total fruit yield, number of fruits per plant, and fruit size were observed between amended and control plants. The results suggest that the mechanisms through which HSS affected plant growth and development were not associated with an improved nutrient uptake. Although the identity of the growth-promoting factors remains to be found, the results suggest that they may be linked to the chemical structure of the humic substances.
Revista:
Journal of Agricultural and Food Chemistry
ISSN:
0021-8561
Año:
2011
Vol.:
59
N°:
20
Págs.:
11129 - 11140
The improvement of the nutritional quality of lettuce by its association with arbuscular mycorrhizal fungi (AMF) has been recently reported in a previous study. The aim of this research was to evaluate if the fertilization with three P sources differing in water solubility affects the effectiveness of AMF for improving lettuce growth and nutritional quality. The application of either water-soluble P sources (Hewitt's solution and single superphosphate) or the water-insoluble (WI) fraction of a ¿rhizosphere-controlled fertilizer¿ did not exert negative effects on the establishment of the mycorrhizal symbiosis. AMF improved lettuce growth and nutritional quality. Nevertheless, the effect was dependent on the source of P and cultivar. Batavia Rubia Munguía (green cultivar) benefited more than Maravilla de Verano (red cultivar) in terms of mineral nutrients, total soluble sugars, and ascorbate contents. The association of lettuce with AMF resulted in greater quantities of anthocyanins in plants fertilized with WI, carotenoids when plants received either Hewitt's solution or WI, and phenolics regardless of the P fertilizer applied.
Autores:
Mellisho, C. D.; González-Barrio, R.; Ferreres, F.; et al.
Revista:
JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE
ISSN:
0022-5142
Año:
2011
Vol.:
91
N°:
12
Págs.:
2132 - 2139
BACKGROUND This study was designed to describe the phenolic status of lemon juice obtained from fruits of lemon trees differing in iron (Fe) nutritional status. Three types of Fe(III) compound were used in the experiment, namely a synthetic chelate and two complexes derived from natural polymers of humic and lignine nature.
RESULTS All three Fe(III) compounds were able to improve the Fe nutritional status of lemon trees, though to different degrees. This Fe(III) compound effect led to changes in the polyphenol content of lemon juice. Total phenolics were decreased (~33% average decrease) and, in particular, flavanones, flavones and flavonols were affected similarly.
CONCLUSION Iron¿deficient trees showed higher phenolic contents than Fe(III) compound¿treated trees, though Fe deficiency had negative effects on the yield and visual quality of fruits. However, from a human nutritional point of view and owing to the health¿beneficial properties of their bioavailable phenolic compounds, the nutritional quality of fruits of Fe¿deficient lemon trees in terms of phenolics was higher than that of fruits of Fe(III) compound¿treated lemon trees. Moreover, diosmetin¿6,8¿di¿C¿glucoside in lemon juice can be used as a marker for correction of Fe deficiency in lemon trees.
Autores:
A. (Autor de correspondencia); Martinez-Alcantara, B.; San-Francisco, S.; et al.
Revista:
EXPERIMENTAL AGRICULTURE
ISSN:
0014-4797
Año:
2011
Vol.:
47
N°:
1
Págs.:
159 - 171
Citrus clementine cv. "Nules" is a seedless mandarin with excellent quality for consumption as fresh fruit; however, its poor fruit set leads to an excess of small-sized fruits. Currently, the only available practice to increase fruit set is the use of the growth regulator gibberellic acid (GA3) as a foliar spray. A trial was conducted to compare an environmentally friendly new bioregulator (MX), containing methyl-xanthine, to GA3 in terms of increasing fruit set and yield of clementine cv. Nules mandarin trees. Fruit yield was significantly increased in treated trees from 17.4 to 25.7% for GA3 and MX treatments, respectively, compared to untreated control trees, without any significant differences between the growth regulators. At the tested doses, MX performed similarly to GA3 in terms of fruit quality and nutrient content, while colour index was not affected significantly by this new bioregulator. A single foliar application of MX was enough to increase fruit set. Spray application of MX on clementine mandarins at the end of the flowering period, when all petals have fallen showed a similar response to GA3 treatments.
Revista:
APPLIED SOIL ECOLOGY
ISSN:
0929-1393
Año:
2011
Vol.:
47
N°:
2
Págs.:
106 - 110
Effects of indoleacetic acid (IAA) and ethylene (E) precursors on microbial biomass, respiration, and various hydrolase activities of the rhizosphere and bulk soil, were studied using a model system simulating this environment. The effects of IAA and E precursors were compared to those of glucose-C, N and S (GNS) applied at the same rate to soils. None of the treatments significantly affected respiration rates and ATP contents of soils. The IAA precursor significantly increased phosphatase, ß-glycosidase, urease and protease activities of the rhizosphere layer of both soils; the E precursor significantly increased phosphodiesterase, urease and protease activities of both soils. The GNS treatment did not significantly increase any hydrolase activity. The IAA precursor also stimulated the phosphatase activity of the bulk layer of the sandy soil after 7 d of incubation, possibly due to its diffusion from the rhizosphere to the bulk soil, whereas no stimulation in the bulk soil layer was observed in either E or GNS treatments. The increased hydrolase activities in the rhizosphere upon addition of both IAA and E precursors may be due to the role of these precursors as microbial metabolic activators, and may be involved in stimulation of plant growth through other processes involving IAA and E producing root associated microorganisms.
Revista:
JOURNAL OF PLANT PHYSIOLOGY
ISSN:
0176-1617
Año:
2010
Vol.:
167
N°:
8
Págs.:
633 - 642
Numerous studies have reported the ability of humic substances to increase shoot growth in different plant species cultivated under diverse growth conditions. However, the mechanism responsible for this effect of humic substances is poorly understood. It is possible that the shoot promoting effect of humic substances involves a primary effect on root H(+)-ATPase activity and nitrate root-shoot distribution that, in turn, causes changes in the root-shoot distribution of certain cytokinins, polyamines and abscisic acid, thus affecting shoot growth. We investigated this hypothesis in the present study.
The results showed that the root application of a purified humic acid causes a significant increase in shoot growth that is associated with an enhancement in root H(+)-ATPase activity, an increase in nitrate shoot concentration, and a decrease in roots. These effects were associated with significant increases in the shoot concentration of several cytokinins and polyamines (principally putrescine), concomitant with decreases in roots. Likewise, these changes in the root-shoot distribution of diverse active cytokinins correlated well to significant changes in the root-shoot distribution of several mineral nutrients.
These results, taken together, indicate that the beneficial effects of humic substances on shoot development in cucumber could be directly associated with nitrate-related effects on the shoot concentration of several active cytokinins and polyamines (principally putrescine).
Revista:
JOURNAL OF MEDICINAL FOOD
ISSN:
1096-620X
Año:
2010
Vol.:
13
N°:
4
Págs.:
863 - 869
Humic acids are compounds resulting from decomposition of organic matter. Despite their common presence, our knowledge of their biological effects is limited, and current findings are controversial. We decided to evaluate the immunological effects of two different types of humic acids, differing in source and biochemical characteristics. Using both components either alone or in combination with the well-established yeast-derived immunomodulator glucan, we measured their effects on both the cellular (phagocytosis and tumor suppression) and humoral (antibody production and cytokine secretion) branches of immune reactions. In summary, our results suggest that humic acids are biologically active immunodulators affecting both the humoral and cellular branches of immune reactions. In addition, the two humic acids studied here are working in synergy in stimulation of the immune reaction, supporting further studies of these natural immunomodulators.
Revista:
JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE
ISSN:
0022-5142
Año:
2010
Vol.:
90
N°:
3
Págs.:
357 - 369
BACKGROUND: In certain plant species, ammonium or urea nutrition can cause negative effects on plant development which can result in toxic symptoms. Some authors suggest that the presence of nitrate can alleviate these symptoms by increasing ammonium and urea assimilation, avoiding its accumulation. In order to study this hypothesis, wheat (Triticum aestivum L.) seedlings were grown with various nitrogen supplies containing the main nitrogen forms (ammonium, nitrate and urea). Amino acids content and the activity of the three main enzymes involved in nitrogen assimilation (nitrate reductase, glutamine synthetase and urease) were studied.
RESULTS: The application of nitrate along with urea and/or ammonium was not associated with a time¿sustained increase in the activity of glutamine synthetase and urease. Amino acid analysis revealed that nitrate induced changes in amino acid metabolism enhancing its concentration. Likewise the content of protein was also higher in nitrate¿treated plants.
CONCLUSION: These results suggest that the effect of nitrate is compatible with a rapid and transient increase in the activity of glutamine synthetase and urease during the first hour after the onset of treatments. Nevertheless, a possible effect of nitrate reducing ammonium accumulation through the activation of alternative metabolic pathways different from that involving glutamine synthetase cannot be ruled out.
Revista:
JOURNAL OF ENVIRONMENTAL QUALITY
ISSN:
0047-2425
Año:
2010
Vol.:
39
N°:
4
Págs.:
1486 - 1497
Revista:
SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
ISSN:
0361-5995
Año:
2010
Vol.:
74
N°:
1
Págs.:
74 - 86
An adequate knowledge of the chemical and structural features that characterize the main fractions of humic
substances in solution is of great interest to better understand a number of processes occurring in nature. Qualitative
analysis of the spectra derived from diverse analytical techniques is frequently complicated, however, partially
due to the quantity and complexity of the data. In this context, multivariate statistical analysis has proven to be a
useful tool to integrate and interpret all this information. In this study, we applied Pareto analysis to the spectrum
data derived from the application of diverse analytical techniques to several samples of humic substances. The
humic substances considered in the study belong to the following groups: gray humic acid (GHA), brown humic
acid (BHA), and fulvic acid (FA). The analytical techniques applied were ultraviolet¿visible light, synchronous
fluorescence, and Fourier transform infrared spectroscopies, 13C nuclear magnetic resonance spectrometry,
and pyrolysis gas chromatography¿mass spectrometry. The results show the efficiency of Pareto analysis at
discriminating between the different groups of humic substances. Th is discrimination corresponded to specific
spectral regions for each group, which corresponded to singular structural features. Thus, GHA presented a marked
aliphatic character and low functionality. The BHA group presented high structural homogeneity characterized by
a high aromatic character,
Revista:
JOURNAL OF PLANT PHYSIOLOGY
ISSN:
0176-1617
Año:
2010
Vol.:
167
N°:
15
Págs.:
1264 - 1272
Ammonium can result in toxicity symptoms in many plants when supplied as a sole nitrogen source. Nitrate reduces the negative effects caused by ammonium and promotes plant growth. In order to explore the mechanism responsible of this beneficial effect, we investigated whether nitrate application causes significant changes in the indoleacetic acid (IAA)- and cytokinin-plant distribution and abscisic acid (ABA) accumulation in wheat (Triticum aestivum L.) plants grown with ammonium. Two differentdoses of nitrate were supplied to ammonium-fed plants (100 mu M and 5 mM), to determine whether the effects of nitrate require significant doses (nutritional character), or can be promoted by very low doses (signal effect).
The results showed that the presence of NO(3)(-) was associated with clear increases in the active forms of cytokinins (zeatine (Z), trans-zeatine riboside (tZR), isopentenyl adenosine (IPR)) and reduction of the levels of the lower active forms (cis-zeatine riboside (cZR)), independently of the dose applied. Likewise. the presence of nitrate also enhanced IAA shoot content, which correlated with higher cytokinin levels and a tendency toward lower ABA concentration. This study presents further evidence that the possible signal effect of NO(3)(-) involved in its beneficial effect on the growth of wheat plants fed with NH(4)(+) could be mediated by a coordinated action of the levels of cytokinins, IAA and ABA in the shoot.
