Effect of cadmium hyperaccumulation on antioxidative defense and proline accumulation of Solanum nigrum L.

Changes in cadmium (Cd) accumulation, the activity of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and the concentrations of malondialdehyde (MDA), chlorophyll and free proline in Solanum nigrum, Cd-hyperaccumulator were examined and compared with a non-hyperaccumulator, Solanum lycopersicum L. It was indicated that the root and leaf SOD, POD and CAT activities of S. nigrum were significantly higher than that of S. lycopersicum. In comparison with S. nigrum, there was a decrease in the growth and chlorophyll content, and an increase in MDA concentrations in the roots and leaves of S. lycopersicum. Although lipid peroxidation was promoted in both S. nigrum and S. lycopersicum by high Cd stress, higher increase occurred in the tissues of S. lycopersicum. The concentration of free proline in the leaves and roots of S. nigrum was higher than those in S. lycopersicum across all the Cd treatments. These results showed that the Cd-hyperaccumulator, S. nigrum had a greater capacity than S. lycopersicum to adapt to oxidative stress caused by Cd.