Hydrogen peroxide potentiates defense system in presence of sulfur to protect chloroplast damage and photosynthesis of wheat under drought stress

The involvement of hydrogen peroxide (H2O2) combined with sulfur (S) was studied in the protection of the photosynthetic performance of wheat (Triticum aestivum L.) under drought stress. The mechanisms of S-assimilation, the activity of antioxidants, glucose sensitivity, water and osmotic relations and abscisic acid (ABA) content were the focus. The combined application of 50 mu M H2O2 and 100 mg S kg(-1) soil (sulfur) resulted in a marked increase in S-assimilation and activity of antioxidant enzymes, with decreased glucose sensitivity and ABA content causing improvement in the structure and function of the photosynthetic apparatus under drought stress. The photosynthetic performance, pigment system (PS) II activity, and growth were improved conspicuously by H2O2 in the presence of S, as H2O2 induced S-assimilation capacity, the activity of antioxidant enzymes, and GSH synthesis under drought stress. Our study shows that H2O2 is more effective in the reversal of drought stress in the presence of S through its influence on S-assimilation, glucose sensitivity, and antioxidant system. These results provide evidence for the effectiveness of H2O2 in improving photosynthesis under drought stress in the presence of S.