The study of the interactive effects of ethylene and salicylic acid on induction of oxidative stress and the mechanisms of tolerance in Brassica napus L

Studies have shown that salicylic acid (SA) is the caused of resistance the plants to environmental stress (cold, heat, salinity and drought stress). The effects of salicylic acid are probably caused by inhibition of ethylene biosynthesis. In this research the effects of ethylene and salicylic acid treatments on the quantity of carotenoid, anthocyanin, flavonoids, lipid peroxidation, ascorbic acid, dehydroascorbic acid and total ascorbate in leaves of canola were studied. The plants were grown in pots until they grow to 4 leaf stages. Therefore the leaves were sprayed with salicylic acid at 4 levels (0, 0.5, 1 and 1.5 mM) lasted for 2 days. Plants were treated with 4 level of ethylene (0, 50, 100 and 150 ppm) for 3 days. Triton X-100 was used as surfactant. At the end of ethylene treatment parameters were measured. Study showed that in those plants which were treated with ethylene and salicylic acid (lower than 1mM), anthocyanin were decreased. Combination treatment of salicylic acid and ethylene caused significant increase in flavonoids, ascorbic acid, dehydroascorbic acid and total ascorbate. Lipid peroxidation in plants that were treated with either salicylic acid or ethylene was increased significantly but combination treatment with salicylic acid and ethylene caused decreased in lipid peroxidation. Our results showed that salicylic acid at 1mM concentration or lower can be used as a antistress agent to reduce oxidative stress caused by ethylene but salicylic acid at 1.5 mM salicylic acid will enhance stress. Therefore we concluded that application of salicylic acid at lower than 1mM can protect plants against oxidative stress.