Evidence for Enhancement of Salinity Induced Oxidative Damages by Salicylic Acid in Radish (Raphanus sativus L.)

In recent years some research results have appeared that exogenous salicylic acid provided significant mitigation effect against salinity induced injuries in plants. An experiment was conducted to investigate the effects of salt stress and salicylic acid on radish (Raphanus sativus L.) plants. After appearing first leaves، plants were treated by salicylic acid (0. 2 mM) for 3 days and NaCl (180 mM) applied 48 hours after first treatment of salicylic acid. Results showed that salt stress decreased fresh weight of shoots and roots، chlorophyll a، chlorophyll b، anthocyanins and flavonoids contents of leaves. In opposite، this stress increased amount of leaves carotenoids، and both leaves and roots phenolic compounds، hydrogen peroxide، proline and lipid peroxidation content. Salicylic acid had similar effects on these factors. Applying salicylic acid in the saline condition decreased fresh weight of shoot and root، chlorophyll a، chlorophyll b، flavonoids، membrane stability index and increased amount of anthocyanins، carotenoids of leaves، phenolic compounds، proline، hydrogen peroxide، lipid peroxidation of leaves and root. We concluded that benefit of exogenous salicylic acid can be dose dependent and salinity plus salicylic acid، at concentrations applied in this study، were established potent secondary oxidative stress in plants.