Effects of Exogenous Spermidine on Growth and Active Oxygen Metabolism in Cucumber Seedlings under Ca(NO_3)_2 Stress

With special cucumber varieties for greenhouse 'Jinyou 3' as materials,effects of exogenous spermidine(Spd,1 mmol·L-1) on seedling growth and active oxygen metabolism in cucumber seedlings under 60 mmol·L-1 Ca(NO3)2 stress were investigated by hydroponic culture.The results showed that under Ca(NO3)2 stress,the O-·2 producing rate increased,the activities of SOD,POD and CAT were significantly higher than those of control.The content of MDA and relative electric conductivity were significantly increased,while the seedlings height,the fresh and dry weight were significantly decreased.Exogenous spermidine application on the leaf further increased the activities of antioxidant enzyme,increased scavenging of reactive oxygen,which reduced the content of MDA,the O-·2 producing rate and relative electric conductivity were decreased.These results show that exogenous Spd can effectively remove the reactive oxygen species and reduces the damage from membrane lipid oxidative,by which mitigate the harmful effects from Ca(NO3)2 stress on plants,and promote the growth of cucumber.