Resumen:
This work aims to characterize the physiological response of grapevine (Vitis vinifera L.) cv. Tempranilloto UV-B radiation under water deficit conditions. Grapevine fruit-bearing cuttings were exposed tothree levels of supplemental biologically effective UV-B radiation (0, 5.98 and 9.66 kJ m¿2day¿1) andtwo water regimes (well watered and water deficit), in a factorial design, from fruit-set to maturityunder glasshouse-controlled conditions. UV-B induced a transient decrease in net photosynthesis (Anet),actual and maximum potential efficiency of photosystem II, particularly on well watered plants. Methanolextractable UV-B absorbing compounds (MEUVAC) concentration and superoxide dismutase activityincreased with UV-B. Water deficit effected decrease in Anetand stomatal conductance, and did notchange non-photochemical quenching and the de-epoxidation state of xanthophylls, dark respirationand photorespiration being alternative ways to dissipate the excess of energy. Little interactive effectsbetween UV-B and drought were detected on photosynthesis performance, where the impact of UV-Bwas overshadowed by the effects of water deficit. Grape berry ripening was strongly delayed when UV-Band water deficit were applied in combination. In summary, deficit irrigation did not modify the adaptiveresponse of grapevine to UV-B, through the accumulation of MEUVAC. However, combined treatmentscaused additive effects on berry ripening.
