[Effects of Cd on rape growth and antioxidant enzyme system]

The study with pot experiment showed that the fresh weights of rape plant and leaf decreased with increasing Cd concentration, and the decrease of leaf fresh weight resulted in the decrease of whole plant fresh weight. The permeability of cell membrane and the content of MDA increased with increasing Cd concentration. When the concentration of Cd was 20 mg x kg(-1), compared with the control, cell membrane permeability and MDA content were increased by 29.68% and 15.19% respectively, and there was a significant correlation between these two indices. When the Cd concentration was 5 mg x kg(-1), the contents of chlorophyll a, b and a + b reached their peaks, and were 23.97%, 33.63% and 26.45% higher than the control, respectively. Cd stress had no significant effect on carotenoid content. The sensibility of the pigments to Cd stress was chlorophyll b> chlorophyll a> chlorophyll a + b> carotenoid, and that of protective enzymes was POD>CAT>SOD. The IC50 of test physiological indices suggested that rape could only grow well on the soil with < 5 mg x kg(-1) Cd.