Effects of Methyl Jasmonate Spray on Alleviation of Cold Stress Induced Oxidative Damages in Cucumber Seedlings

Cold induced oxidative stress has a negative effect on biomembranes and metabolic process of plants. In this study, the effects of foliar application of methyl jasmonate (MeJA) on lipid peroxidation, hydrogen peroxidase, total phenol, soluble proteins and some antioxidant enzyme activities including superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX) and ascorbate peroxidase (APX) of greenhouse- grown cucumber (Cucumis sativus L. cv ‘Negin’) was investigated under cold stress. The seedlings was sprayed with MeJA in four concentrations [0 (control), 50, 100, 200 µM] at 4 leaves stage. Twenty-four hours after foliar spraying with MeJA, half of the controls and half of the MeJAtreated plants were subjected to 4 °C for 12 h followed by a recovery period of 3 days in optimum conditions, and the rest of the plants remained at 24 °C. Cold stress increased the malondialdehyde and H2O2 level in seedling leaves, whereas foliar MeJA treatment dramaticaly reduced these memberance deliterios indices. Soluble proteins and total phenol content was higher in the MeJA-treated plants than in the controls. MeJA especially at 100 and mainly 200 µM significantly increased the activities of SOD, CAT, GPX and APX in cold-stressed cucumber seedling. It seems that MeJA through increasing in some osmoregulant such as soluble protein and antioxidant enzyme activities as well as phenolic compounds helped to reduce the harmful effects of cold stress which finally led in cell membrane stability.