Cadmium accumulation and antioxidative responses in the Sesbania drummondii callus

The effect of cadmium (Cd) on growth, accumulation, and antioxidative response was studied in Sesbania drummondii callus, cultivated on different concentrations of Cd (0-250 microM) for four weeks. Callus growth was comparable to that of the control for concentrations up to 50 microM Cd; however, concentrations higher than 50 microM affected growth. A concentration of 100 microM Cd inhibited growth by 16%, with respect to control. Cd concentration in callus increased with increasing Cd concentrations in the growth medium. Callus accumulated 530 mg Cd kg(-1) of their dry weight at 100 microM Cd concentration. Sesbania callus responded to Cd-induced oxidative stress by modulating antioxidants (glutathione and other non-protein thiols) level and antioxidative enzymes: superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR). The content of the glutathione (GSH) and GSH/GSSG ratio first increased up to a concentration of 50 microM Cd and then decreased. The content of other non-protein thiols significantly increased with increasing Cd concentrations in the growth medium. The activities of antioxidative enzymes, SOD, APX, and GR, followed the same trends as antioxidants first increasing up to a concentration of 50 microM Cd and then decreasing. These results suggest that antioxidative defense mechanisms play a significant role in Cd detoxification and accumulation in Sesbania drummondii.