The Physiological Effects Of Exogenous Cysteine And Nitric Oxide On Alleviating Cd Toxicity In Cucumber

With the rapid development of industry, cadmium pollution not only seriouslypollutes the soil, but also negatively affects normal growth of the plant, and could causethreat to human health through food chain. It was reported that the cucumber seedsgermination and seedlings growth was sensitive to the cadmium stress, therefore, aninvestigation of how to alleviate the inhibition of cadmium stress on cucumber germinationand plant growth has an important significance. At the present report, the roles of nitric oxideand cysteine in alleviating cadmium stress were studied, the specific results are as follows:（1） Exogenous cysteine could effectively alleviate the inhibitory effect of cadmiumstress on cucumber seeds germination, and facilitate the elongation of hypocotyls and radicals.Cadmium treatment significantly induced accumulation of MDA and H₂O₂in cucumberhypocotyls and radicals, and application of cysteine dramatically reduced the contents ofMDA and H₂O₂. Moreover, cysteine could also alleviate the impairment of cadmium stress oncucumber through improving activities of antioxidant enzymes and antioxidant capacity.（2） Using SNP as an exogenous NO donor could significantly relieve the inhibition ofcadmium stress on the growth of cucumber seedlings. SNP could promote the growth ofseedlings and alleviate the inhibitory effect of cadmium stress on cucumber growth. Cadmiumtoxic resulted in an obvious chlorosis of leaves, however, SNP additive treatment increasedthe pigment content, and improved net photosynthetic rate, transpiration rate, and stomatalconductance. Meanwhile, SNP could increase activities of antioxidant enzymes andantioxidant capacity and decrease contents of MDA and H₂O₂.