The Effect of Foliar Application of Some Chemical Compounds on ‎Antioxidant Enzymes Activity and Chlorophyll Fluorescence of Sunflower ‎in Different Irrigation Conditions

In order to evaluate the effect of foliar application of some chemicals on antioxidant enzymes activity and chlorophyll fluorescence of sunflower in different irrigation conditions as well as identifying compounds’ effectiveness in reducing the adverse effects of drought stress, this experiment has been conducted at the Agricultural Research Center of Hamedan, Iran, between 2015 and 2016. Three irrigation and six foliar application treatments are evaluated in a split plot experiment based on randomized complete block design with three replications. Irrigation treatments consist of 60%, 80%, and 100% plant water requirement and foliar application treatments include abscisic acid 40 μM, Selenium 20 mg/L, Salicylic acid 500 μM, SNP 100 μM, Glycine betaine 100 mM, and the control. Results show that by decreasing the irrigation water, the activity of superoxide dismutase, peroxidase, and catalase enzymes rise sharply, while the maximum photochemical efficiency of photosystem II and grain yield decline. The interaction effect of irrigation × foliar application on the activity of antioxidant enzymes and grain yield is significant, but not so on chlorophyll fluorescence. In deficit irrigation treatments, foliar application of all chemical compounds significantly boost the activity of antioxidant enzymes, compared to the control. Application of salicylic acid raises the maximum photochemical efficiency of photosystem II and grain yield, at all irrigation conditions. Under 60%, 80%, and 100% irrigation conditions, salicylic acid application increases grain yield by 24.3%, 10.1%, and 4.9%, respectively.