Interactive effects of lead, copper, nickel and zinc on growth, metal uptake and antioxidative metabolism of Sesbania drummondii

Sesbania drummondii seedlings were grown in a medium to which lead (Pb), copper (Cu), nickel (Ni) and zinc (Zn) were added singly and in combinations in order to assess the effects of metal interactions on seedling growth, metal accumulation and anti-oxidative system. S. drummondii growth was significantly inhibited with metal treatments. S. drummondii accumulated substantially higher concentrations of metals in the roots than shoots. The uptake of metals followed the order Pb > Cu > Zn > Ni in roots and Pb > Zn > Cu > Ni in shoots. In addition, uptake of a single metal by S. drummondii was affected by the presence of a second metal, suggesting an antagonistic effect or competition between metals at the plant uptake site. A significant increase in both enzymatic [superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR)] and non-enzymatic (glutathione) antioxidant was observed in the S. drummondii seedlings exposed to different metal treatments. The enhancement in enzyme activities followed the order of Cu > Ni > Pb > Zn. However, compared to the effect of individual metal, metals in combination increased the enzyme activities to varying degrees.