Exogenous nitric oxide alleviates high temperature induced oxidative stress in wheat (Triticum aestivum L.) seedlings by modulating the antioxidant defense and glyoxalase system

We investigated the protective role of exogenous nitric oxide (NO) in alleviating high temperature induced damages of wheat (Triticum aestivum L. cv. Pradip) seedlings. Heat treatment (38 °C) alone or in combination with 0.5 mM SNP (a NO donor) was applied with nutrient solution on 8-d-old hydroponically grown seedlings for a period of 24 h and 48 h. Heat stress significantly decreased the Chl content and increased the lipid peroxidation (MDA) and H2O2 levels in time depending manners. Ascorbate (AsA) content markedly decreased upon heat treatment but glutathione (GSH) and glutathione disulfide (GSSG) content increased. Heat treatment resulted in an increase of the activities of antioxidant enzymes ascorbate peroxidase (APX), glutathione reductase (GR), glutathione peroxidase (GPX) and glutathione S-transferase (GST). The activities of glyoxalase enzymes also increased upon heat stress. Exogenous NO supplementation in the seedlings had little influence on the nonenzymatic and enzymatic components compared to the control. However, supplementation of heat-treated seedlings with SNP significantly reduced the high temperature induced lipid peroxidation, H2O2 content and increased the content of Chl, AsA and GSH as well as the GSH/GSSG ratio. Heat treated seedlings which were supplemented with SNP also upregulated the activities of APX, MDHAR, DHAR, GR, GST, CAT and Gly I. This study concludes that an exogenous supply of NO protects wheat seedlings from high temperature induced oxidative stress by upregulating antioxidant defense and methylglyoxal (MG) detoxification system.