Abstract: Cucumber seedlings with two true leaves which were spread by spermidine(Spd) of different concentrations were used to study the effect of Spd on their growth, physiological and biochemical characteristics under 5℃ for four days in order to ascertain effects and physiological mechanisms of Spd on chillingtolerance of cucumber. The results showed that Spd at 050 mmol·L^-1 is more effective in improving chillingtolerance of cucumber seedlings. Pretreatment of Spd could improve increase of dry matter and water content, obviously decrease chilling injury index, electrolytic leakage and malondialdehyde(MDA) content, significantly increase activities of superoxide dismutase (SOD), peroxidase(POD), catalase(CAT) and ascorbic peroxidase(APX), content of ascorbic acid, proline and soluble sugar, maintain higher root activity.

Key words: Cucumber, Spermidine, Chillingtolerance, Antioxidant system, Osmotic adjustment