Improving Chilling Resistance of Cucumber Seedlings by Salicylic Acid

Salicylic acid (SA) has been reported to induce a number of defense responses and increase chilling tolerance in plants. Therefore, an experiment was conducted to test whether SA application at various concentrations (0, 0.5, 1 and 1.5 mM) through seed soaking or foliar spray would protect cucumber (Cucumis sativus) seedlings subjected to chilling stress. Thirty five-day old plants were exposed to chilling 5 h/day at 4°C for 5 days. SA improved growth rate of cucumber seedling subjected to chilling stress and increased proline content compared with the control at the end of chilling stress. SA ameliorated the injury caused by chilling stress via inhibiting increases in lipid peroxidation and leaf electrolyte leakage, which suggested that SA ameliorated the negative effect of chilling stress. SA was most effective in increased chilling tolerance of cucumber seedling when applied using the seed soak method than as a foliar spray. The best protection appeared to be obtained from seedlings that seed soaked with SA at 0.5 and 1mM.