不同光强下龙葵对镉的吸收积累及生理响应

采用土培方法探讨了不同光强（自然光和50%遮光）和镉（Cd）不同添加量（0、 25、 50、 75和100 mg/kg）复合处理下，龙葵对Cd的吸收累积特征，超氧化物歧化酶（SOD）、 过氧化物酶（POD）、 过氧化氢酶（CAT）和抗坏血酸过氧化物酶（APX）活性以及叶绿素、 丙二醛（MDA）、 谷胱甘肽（GSH）和植物螯合肽（PCs）含量等的变化特征。结果表明， 自然光条件下龙葵叶绿素b、 叶绿素a+b以及地上和地下部Cd富集量均显著低于遮光处理; 叶和根的SOD、 POD、 CAT和APX活性在自然光条件下随土壤Cd添加量的增大先升后降，而在遮光处理下则持续升高; 除Cd 25 mg/kg处理时根POD及叶CAT活性在不同光强处理下没有显著差异外，其余Cd添加量处理下SOD、 POD、 CAT和APX活性在自然光条件下均显著高于遮光处理; 自然光条件下龙葵叶和根的MDA含量显著高于遮光处理，而叶和根的GSH含量和叶中PCs含量均显著低于遮光处理。研究结果表明，遮光环境促进了龙葵对Cd的富集，并且减轻了Cd对龙葵的氧化胁迫。

Cd bio-accumulative characteristics and physiological response of Solanum nigrum L. under different light intensities

Under different light intensities (natural light and 50% shading), bioaccumulation of Cd, activities of antioxidative enzymes (SOD, POD, CAT and APX), and contents of chlorophyll, MDA, GSH and PCs of Solanum nigrum L. with different Cd concentration treatments (0, 25, 50, 75 and 100 mg/kg) were investigated. The results show that the contents of chlorophyll b and a+b of leaves of  S. nigrum L. and Cd accumulations in shoots and roots of S. nigrum L. grown under the natural light are significantly lower than those under the shading. With the increase of Cd concentration, the activities of SOD, POD, CAT and APX in leaves and roots of S. nigrum L. are decreased after an initial increase under the natural light, while those grown under the shading environment are increased consistently. The root POD activity and leaf CAT activity under the treatment of 25 mg/kg Cd have no significant differences between the natural light and the shading environment, however, in the treatments of the other Cd concentrations, the activities of SOD, POD, CAT and APX of leaves and roots of S. nigrum L. grown under the natural light are significantly higher than those under the shading. The MDA contents in leaves and roots of S. nigrum L. under the high light are significantly higher than those under the shading environment, while the GSH and PCs contents in leaves and roots of S. nigrum L. under the natural light are significantly lower than those under the shading environment. These results indicate that the shading environment promotes the Cd accumulation of S. nigrum L. and reduces the oxidative stress of Cd to S. nigrum L.