Response of antioxidant system of tomato to water deficit stress and its interaction with ascorbic acid

Environmental stresses including water deficit stress may produce oxidants such as reactive oxygen species that damage the membrane structure in plants. Among the antioxidants، ascorbic acid has a critical role in the cell and scavenges reactive oxygen species. In this research، effects of ascorbic acid at two levels (0 and 10 mM) and water deficit stress based on 3 levels of field capacity (100، 60 and 30%) were studied in tomato plants. Both levels of stress increased lipid peroxidation، reduced the amount of ascorbic acid and glutathione and increased the activity of enzymes superoxide dismutase، catalase، ascorbate peroxidase، glutathione reductase، guaiacol peroxidase and reduced the growth parameters. Ascorbic acid treatment، reduced lipid peroxidation، increased ascorbic acid and glutathione levels and decreased the activity of superoxide dismutase، catalase، ascorbate peroxidase، glutathione peroxidase and guaiacol peroxidase and positive effects of ascorbic acid treatment appeared to improve the plant growth parameters.