effect of exogenous application of proline and glycine betaine on biochemical alterations in grapevine under drought stress

proline and glycine betaine are the most common compatible solutes that prevent plants from destructive effects of osmotic stresses by osmotic adjustment and protection of membranes, proteins and enzymes. it has been reported that exogenous application of these compounds, can increase plant resistance to drought stress. therefore a factorial experiment based on randomized complete block design with four replications was performed in four grapevine cultivars (‘khushnav’, ‘peykani’, ‘perlette’, and ‘flame seedless’). grapevines were irrigated by 70 percent of the vine water requirement, in drought stress treatment. proline (10 mm) and glycine betaine (15 mm) were sprayed on grapevines at four growth stages (before flowering, flowering, sour cluster and veraison). results showed that endogenous proline and amount of glycine betaine, peroxidase and ascorbate peroxidase enzyme activity in treated vines were significantly higher than the control, in both proline and glycine betaine treatments. among of the treated vines, the most and the least amount of proline was measured in ‘flame seedless’ and ‘peykani’, respectively. other measured traits in cultivars did not show significant difference. according to the role of these enzymes in eliminating reactive oxygen spices (ros) and also the role of proline and glycine betaine in antioxidants activating, using of these two osmolytes will be able to increase the vines tolerance to drought stress conditions.