Effects of Exogenous Nitric Oxide on Photosynthesis, Antioxidant Capacity and Proline Accumulation in Wheat Seedlings Subjected to Osmotic Stress

Nitric oxide (NO) is a active molecule involved in mediation of various biotic and abiotic stressinduced physiological responses in plants. In the present study, using SNP (sodium nitroprusside) as NO donor and cPTIO [2-(4-carboxypheny-4,4,5,5-tetramethylimidazoline-1-1oxyl-3-oxide, potassium salt] as specific NO scavenger, we examined the ability of exogenous NO to alleviate oxidative damage, accelerate proline accumulation and enhance photosynthesis in leaves of wheat seedlings subjected to osmotic stress. Wheat seedlings were exposed to Hoagland solution containing 15% polyethylene glycol (PEG), or 15% PEG plus 0.3mmol L SNP or 15% PEG plus 0.3 mmol L SNP and 0.5 mmol L cPTIO for 24 h. The results showed that 1 1 1 osmotic stress induced decrease in superoxide dismutase (SOD) and catalase (CAT) activity and overproduction of O in wheat leaves, which in turn caused exacerbation of lipid peroxidation and depression 2 of photosynthesis. Application of NO donor SNP retarded decrease in SOD and CAT activity, increase in O2 production and hence inhibited lipid peroxidation. As a result, F /F , F /F , |ÕPS2 and Pn in leaves of wheat m o v m seedlings subjected to osmotic stress were increased. Meanwhile, proline accumulation was accelerated and higher relative water content (RWC), and lower leaf water loss (LWL) were maintained by the application w of SNP under osmotic stress. However, such effects of SNP were reversed by the addition of NO scavenger cPTIO. It was indicated that effects of NO on preventing wheat leaves from osmotic stress-induced damage might be specific.