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.