Production, localisation and possible roles of nitric oxide in drought-stressed grapevines

Background and Aims: The aim of this study was to monitor nitric oxide (NO) production in response to progressive soil drying as well as to evaluate its possible role as an intermolecular signalling molecule mediating drought-stress responses in grapevines. Methods and Results: NO production in response to water stress was examined in potted grapevine plants (Vitis vinifera L. cv. Mavrodafni). The cellular sites of NO production and localisation in stressed plants were monitored by fluorometric techniques. Results indicated that both abscisic acid and NO concentrations increased significantly in leaves of stressed plants. The stomatal guard cells seemed to be the sites of earlier NO accumulation. The changes in stomatal conductance seemed to be closely related to both abscisic acid and NO increase, while there was no significant correlation between stomatal conductance and hydrogen peroxide concentration. Conclusions: The close relationships between stomatal conductance and NO concentrations indicate a potential role of this molecule in drought-signalling pathway in grapevines. Significance of the Study: Results suggest a contribution of hydrogen peroxide to triggering NO production as well as a possible role of NO on both stomatal closure and antioxidant defence in drought-stressed grapevines.