SALICYLIC ACID TREATMENT INCREASES SALT TOLERANCE OF WHEAT PLANTS BY ENHANCING ANTIOXIDANT DEFENSE SYSTEMS

The present study was conducted to assess influence of salinity and varying concentrations of salicylic acid (0.5 mM and1mM SA) on growth, antioxidant enzyme activities and biochemical activities of wheat plants. Wheat (cv. Sods 12) was grown in a normal clay soil for 30 days. The treatments comprised of control, 50 mM NaCl, 100 mM NaCl, and 150 mM NaCl. Except control, the concentrations of NaCl at all levels were applied through irrigation. After harvest, the plant samples were analyzed for photosynthetic pigments, proline content, electrical conductivity, and cell membrane stability. The results show significant decline in vegetative parameters (e.g., dry mass) at higher application rates of salinity and SA (1 mM SA + NaCl) as compared to control treatment. The phenolic compounds and ascorbic acid concentrations were reduced after application of 0.5 mM SA and combined application of NaCl and SA, while the concentration of Milondialdehyde (MDA) was gradually increased by increasing SA application and were maximum at the highest application level of combined NaCl and 1 mM SA. The level of antioxidant defense systems (catalase and ascorbate peroxidase) increased in response to salicylic acid treatment.Enhanced antioxidant activities helped to decrease oxidative damage from salt and develop tolerance against salt stress insalicylic acid -treated wheat plants. The data provided evidence that salicylic acid treatment reduced the adverse effects of salt stress on wheat plants, and might play a key role in providing stress tolerance by stimulation of the antioxidant system as a stress protection mechanism.