Abstract
Nowadays, the application of antioxidants and plant growth regulators is assumed to decrease the negative effect of different stresses. Ascorbic acid and Sodium nitroprusside have been substances that increase the resistance to biotic and abiotic stresses. To evaluate this on safflower (Carthamus tinctorius), a field experiment was carried out in split plot factorial based on randomized complete block with three replications. Two levels of irrigation, including 8 days interval (well watered) and 16 days interval (water deficit stress) were, in the main plot, and the foliar application of sodium nitroprusside in 3 levels (0, 50 and 100 µm) and Ascorbic acid in 3 levels (0, 10 and 20 mm) was in sub plots. Stress treatment was applied after plants establishment completely. The first foliar application of sodium niroprusside and ascorbic acid was performed in 63 and 65 days after sowing respectively and then repeated after 1 week. Water decreased membrane Electrical Conductivity (EC). The EC decreased by ascorbic acid foliar application. The EC increased significantly by sodium nitroprusside foliar application. The foliar application of sodium nitroprusside increased leaf area index. Chlorophyll b increased by sodium nitroprusside foliar application in well watered. 10 mm ascorbic acid foliar application increased Carotenoeid. Seed yield by the application of 100 µM sodium nitroprusside concentration was 13.2% more than control. Therefore, it seems that the foliar application of sodium nitroprusside with appropriate concentration can be helpful in reducing stress intensity.