Drought is the most common environmental stress in vineyard occurs in soils with low water content, even in irrigation condition. To evaluate foliar spraying of ascorbic acid under drought stress, a research during 2012 to 2013 years in the natural environment, and one year after the establishment of the cuttings in clay loam soil was conducted. Cultivars with two-level white seedless and khoshnav, two levels of water stress control (moisture content of 75% field capacity) and drought stress (moisture content of 25% field capacity or irrigation after 7 weeks) with three replications by factorial design in a randomized complete block design were studied.Drought was affected significance difference at 1% statistical level on total physiological characteristics. While the use of AsA had no effect on stability of cell membranes, lipid peroxidation, total soluble protein and leaf ascorbic acid, however was effective significantly different at 5% level ascorbate peroxidase. Cultivars in this study showed significant differences at 1% level in leaf ascorbic acid. AsA 300 mg per liter in Khoshnav under full irrigation caused increase leaf ascorbic acid and decrease ascorbate peroxidase activity as compared to control and this concentration in White seedless under full irrigation caused increase membrane stability and under drought stress decrease total soluble protein compared to the control. The results showed that ascorbic acid can affect some physiological responses of grapes.
