Resumen: A number of studies have demonstrated the key role of nitric oxide in the regulation of many fundamental physiological processes that includes plant responses to abiotic and biotic stresses. On the other hand, beneficial action of humic substances on plant growth has been well corroborated, particularly when plants are subjected to abiotic stresses. Furthermore, several recent works have reported the functional links between the plant growth promoting action of humic substances and nitric oxide production and function in plants. In this article, we try to briefly review and discuss the main results showing the relationships between nitric oxide function and humic substances action on plants, also stressing the nitric oxide-dependent involvement of other plant growth regulators, such as auxin, ethylene, abscisic acid, and cytokinins.
