Exogenous Spermidine (Spd) Alleviate Cucumber Salt Stress And Its Mechanism

Cucumber (Cucumber sativus L.) is annual herbaceous plants of Cucurbitaceae, our cucumber production accounted for30%of world output, not only one of major vegetable worldwide, but also the most widely applied facility cultivation of vegetables. However, with the rapid development of facility cultivation, soil salinization has become the major limiting factors of facility cultivation, its occurrence large area, a wide range and seriously endanger has created a significant economic losses to farmers."JinChun No.4" and "JinLv No.5" were used in the artificial climate incubator with matrix culture methods, and different concentrations of extraneous spermidine (0,50,100,150,200,250mg/L) were applied at cucumber seedlings under200mmol/L NaCl stress to study the changes of the cucumber seedlings growth, chlorophyll content, malondialdehyde (MDA) content, Proline(Pro) content, soluble sugar content, sucrose content,and the starch content. The results are as followsUnder salt stress,the extraneous spermidine pretreatment has an certain role in promoting growth,and with Spd concentration rised, plant height, stem diameter, shoot fresh weight and root fresh weight indicators show first increased and then decreased,and significantly higher than the control.the largest increase accordingly up to20.1%,12.2%,48%.40.5%, the leaf area rises with the Spd concentration.and significantly higher than the control,max increase is up to10.7%.with the Spd concentration rises. Chlorophyll content show first increased and then decreased, leaf chlorophyll content with treatment of150mg/L concentrations Spd is higher than other treatments, the biggest increase reach32.6%; Different concentrations treatment of extraneous Spd can reduce the content of MDA in seedling leaves, and ease the membrane-lipid peroxidation, The treatment of100mg/L extraneous spermidine decreased significantly the content of MDA in seedling leaves, the largest drop can reach to47.4%; A higher concentration of extraneous spermidine(200,250mg/L) can significantly improve the content of Pro, the largest increase up to108.2%; A higher concentration of extraneous spermidine can significantly improve the content of soluble sugar, a lower concentration of extraneous spermidine can significantly improve the content of sucrose content.Based on the physiological index, it could be concluded that a certain concentration of extraneous spermidine can significantly relieve the salt injury and improve salt tolerance of the cucumber seedlings.