Physiological Mechanisms of Salicylic Acid Enhancing the Salt Tolerance of Cucumber Seedling

【Objective】The objective of this study was to gain better insight into the physiological mechanisms of exogenous salicylic acid(SA) on NaCl-tolerance in cucumber(Cucumis sativus L.).【Method】The experiments were performed to investigate the effects of exogenous SA on the physiological parameters in salt-sensitive cultivar(Xinjinyan No.4) under NaCl stress.Cucumber seedlings were treated by rhizosphere injection and foliar spray of 50 mg·L-1 SA ,and were then subjected to NaCl stress.【Result】SA treatment increased the contents of soluble sugar and proline by 110.4%.There was an 82.2% increase in cucumber leaves compared to untreated plants.Exogenous SA increased the activities of superoxide dismutase,peroxidase and catalase under NaCl stress but decreased the superoxide dismutase activity under non-NaCl stress in cucumber leaves.The water content of the cucumber plant was significantly increased,but the malondialdehyde content and electrolyte leakage were reduced by 30.9% and 79.9% under NaCl stress with SA than without.The physiological effect of SA was reflected by a significant increase in growth parameters such as plant height,stem diameter and total biomass over only NaCl stress plants.【Conclusion】The exogenous SA may play an important role in NaCl-tolerance of cucumber seedlings by osmotic regulation,antioxidation,water balance and membrane stability.