Effects of exogenous nitric oxide in wheat seedlings under chilling stress.

The effects of nitric oxide (NO) on chilling tolerance (contents of hydrogen peroxide (H2O2) and superoxide anion (O2 (-)) and lipid peroxidation level (malondialdehyde, MDA)) and the activities of antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT)) were investigated in the leaves of wheat (Triticum aestivum L.) exposed to chilling. NO treatment was carried out through spraying of sodium nitroprusside (SNP), which is a donor of NO. To do this, SNP concentrations of 0.1 and 1 mM were applied on the leaves of 11-day plants and the plants were then exposed to chilling conditions (5/2°C) for 3 days. The chilling stress treatment increased both the activities of antioxidant enzymes and the levels of MDA, H2O2 and O2 (-). Similarly, NO treatment enhanced SOD, POX and CAT activities under chilling stress, whereas it decreased H2O2 and O2 (.) (-) contents as well as MDA level. The most effective concentration was determined as 0.1 mM SNP. Exogenous SNP application as a donor of NO was found to have an important ameliorative effect on cold tolerance of seedling exposed to chilling stress by stimulating antioxidant enzyme activity.