Uptake of Heavy Metals, and Antioxidative Enzymes in Brassica juncea L. Seedlings as Affected by Zn in Binary Combinations with Other Heavy Metals

摘要

The present study attempts to understand the uptake of heavy metals and stress tolerance in Brassica juncea L. seedlings under the effect of Zn in binary combinations with Cr, Ni, Co and Cu through the production of antioxidative enzymes - superoxidedismutase (SOD), guaiacol peroxidase (GPX), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR). It was observed that the order of uptake of heavy metals by the seedling in single metal solutions was Zn > Cu > Co > Cr > Ni. Zn in binary combination with other heavy metals, mutually decreased the uptake of each other, the maximum decrease being 66.1% in the uptake of Cr in (CrlOO+ZnlOO) binary solution. All the metals, whether applied singly or in combinations, significantly increased the activities of antioxidative enzymes, except for CAT. Zn was the most effective metal in increasing the activities of antioxidative enzymes. At 100 mg l~(-1) it increased the activities of GR, GPX and APX by 101%, 64%, and 42% respectively, whereasmaximum SOD activity (16 mM UAmg~(-1) protein) was induced by 100 mg Cr. Of all the binary combinations, Zn+Co and Zn+Ni were most effective in increasing the activities of GPX and GR, respectively, whereas Zn+Cu and Zn+Cr increased the activities of APX and SOD, respectively. Binary interaction models revealed that Cr, Ni, Co and Cu act antagonistic to Zn to increase the activity of GR, whereas for GPX, APX and SOD, these metals in binary combinations with Zn, were mutually antagonistic, thereby causing a negative interactive effect. Cr, Co and Cu were mutually antagonistic to Zn for catalase activity, whereas interaction between Ni and Zn was synergistic for this enzyme.