Nickel alters antioxidative defense and water status in green gram

Green gram [Vigna radiata (L.) wikzek] plants exposed to excess nickel (10, 100 and 200 μM) under glass-house conditions were quantified for selected parameters of oxidative stress and water deficit. Supply of excess nickel for 72 h induced chlorosis of young leaves, the effect being most pronounced at 200 μM Ni supply. Excess supply of nickel showed enhanced accumulation of antioxidants ascorbate and dehydroascorbate and decrease in the activity of catalase in the leaves, leading to accumulation of hydrogen peroxide. The activity of ascorbate peroxidase, peroxidase, glutathione reductase and SOD showed an increase. The effect on the enzyme activities varied with the level and duration of Ni supply. Leaves of plants supplied excess Ni showed decrease in water potential (Ψ_L) and relative water content (RWC) and an increase in proline. Results observed indicate that excess supply of nickel interferes with plant water relations and induces oxidative stress.