RESPONSE OF ANTIOXIDANTS AND LIPID PEROXIDATION TO EXOGENOUS APPLICATION OF ALPHA-TOCOPHEROL IN SUNFLOWER (HELIANTHUS ANNUUS L.) UNDER SALT STRESS

Alpha-tocopherol is an antioxidant mainly responsible for detoxification of reactive oxygen species produced during prolonged abiotic stresses as reported in the previous studies. A pot experiment was carried out to study the response of antioxidants and lipid peroxidation to alpha-tocopherol seed soaking treatment in saline conditions. Seeds of sunflower cvs. FH-[572 and 621] were immersed for 16 hours in four alpha-tocopherol levels, [0 (dist. H2O), 100, 200, 300] mg L-1. Thirty five days after seed sowing plants were irrigated with 0 mM and 120 mM (two levels) of salt (NaCl) till final harvest. Leaves were sampled 61 days after seed sowing for biochemical analyses and yield at maturity. Salt stress (120 mM NaCl) caused significant reduction in shoot and root dry weight, total phenolic contents and superoxide dismutase activity and had nonsignificant effect on all yield related parameters. Salt stress showed substantial increase in the activity of enzymatic antioxidants such as catalase, peroxidase and glutathione reductase. Seed soaking with alpha-tocopherol significantly increased shoot and root dry weight, 100 achene weight and total achene weight plant(-1), catalase and peroxidase activity, total phenolic content, ascorbic acid and showed non-significant effect on leaf total soluble proteins and hydrogen peroxide. Alpha-tocopherol pre-sowing seed treatment caused significant reduction in lipid peroxidation. Cultivar FH-621 showed higher salt tolerance and alpha tocopherol 200 and 300 mg L-1 levels effectively increased its yield and dry matter production respectively under salt stress.