Physiological and biochemical changes induced by different irrigation strategies in grapevines

The effects of partial rootzone drying (PRD) and regulated deficit irrigation (RDI) on water relation, gas exchange, abscisic acid (ABA), xylem pH and nitric oxide concentration was examined in two years old own-rooted grapevines (V vinifera L., cv. Savatiano) which were grown with their roots split between two soil columns. The plants were subjected to one of three irrigation treatments: well watered (WW-control) receiving 100% of plant transpiration, PRD with half of the root system exposed to soil drying and the other half kept well watered and RDI with 50% of plant transpiration supplied to both sides of the root system. Results indicated that transpiration rates of plants under PRD and RDI irrigation were significantly lower compared with the control. Decrease in transpiration rate does not seem to be attributed to changes in leaf ABA concentration. Predawn leaf water potential was significantly lower in PRD and RDI treatments compared to the control, but without any significant differences between PRD and RDL Xylem pH increased in stressed plants and there was also a rapid increase in NO-induced fluorescence in the leaves of the stressed plants. The reduction in transpiration rate in both PRD and RDI treatments in relation to the maintenance of photosynthetic rate resulted in significantly higher values of intrinsic water use efficiency.