Investigating the effect of pretreatment of salicylic acid on the germination of aged pumpkin (Cucurbita pepo L.) seeds and antioxidant enzymes of plant under drought stress

With the aim of evaluating the effect of salicylic acid in improving the efficiency of the aged pumpkin seeds under drought stress conditions, a factorial experiment was carried out in the form of a completely randomized design with three replications. Pretreatment of different concentrations of salicylic acid including zero (pretreated with water), 1 and 1.5 mM at different drought levels of zero, -0.2, -0.4 and -0.6 MPa were investigated. Indicators of mean germination time, germination percentage, seedling length, seed vigor, membrane electrolyte leakage, soluble carbohydrates, soluble proteins, malondialdehyde, ascorbate peroxidase activity, superoxide dismutase and catalase enzymes were evaluated. The results showed that the pretreatment of seeds with different concentrations of salicylic acid prevented the significant decrease in the germination indices of the deteriorated pumpkin seeds under drought stress. So that at the potential of -0.6 MPa, the treatment of seeds with 1.5 mM salicylic acid increased the percentage of germination, seed germination index, soluble carbohydrates and soluble proteins respectively 80.2, 169.4, 51.6, 93.4% and for the activity of ascorbate peroxidase, superoxide dismutase and catalase enzymes, 41.2%, 12% and 11.8%, respectively, compared to the control. Based on the research findings, pretreatment of salicylic acid (1.5 mM) is recommended in order to reduce the oxidative stress caused by drought for pumpkin.