Effects of exogenous spermidine on cucumber seedling growth and reactive oxygen metabolism under salt stress

The experiment was carried out to study the effects of exogenous spermidine(Spd) on cucumber seedling growth and reactive oxygen metabolism and antioxidant enzymes gene expression in cucumber(Cucumis sativus L.cv.Jinchun No.2) seedlings under salt stress with solution culture.The plant height,stem diameter,fresh and dry weight were significantly decreased under salt stress,while the O2 ·-production rate,H2O2 content,MDA contents and electrolyte leakage were increased significantly.However,the inhibition of seedling growth could be alleviated by spraying Spd,and the gene expression of Cu/Zn-superoxide dismutase(SOD) and peroxidase(POD) were up-regulated.The activities of SOD,POD enzymes were also increased,meanwhile the O2 ·-production rate,H2O2 content,MDA content and electrolyte leakage were decreased significantly.The results indicated that gene expression of Cu/Zn-SOD and POD could be up-regulated by exogenous Spd,which could increase the SOD and POD enzymes activities and reduce O2 ·-production rate,H2O2 content,MDA content and electrolyte leakage,and alleviate the inhibition of plant growth in salt stress finally.