Physiological Response and Antioxidative Enzymes Alteration Following Nickel Stress in Two Varieties of Macrotyloma uniflorum (Lam) Verdc. at Post Flowering Stage

A pot experiment was conducted using soilamendment with increasing concentration of nickel (control, 25, 50, 100, 150 or 200 mg of nickel/kg of soil) to study the physio-biochemical changes in two varieties (black and white) of M. uniflorum (lam) verdc. at post flowering stage. Seeds of the two different varieties were allowed to grow in each of the nickel concentrations in triplicate. The plant was gently up rooted on day 60 corresponding to post-flowering/fruiting stage. Root and shoot length, fresh and dry weight, root and shoot tolerance index, chlorophyll, proline and protein content of the leaves, and antioxidant enzymes activity such as super oxide dismutase(SOD), catalase(CAT) and guaicol peroxidase(POX) in the leaf extract were estimated. The higher concentrations of nickel in soil reduced the protein content, and root and shoot length, following initial increases at lower concentrations of nickel exposure. There was up regulation in de novo synthesis of antioxidant enzymes at lower concentration of nickel which was followed by a state of oxidative damage, as evidenced by declining activity of these enzymes. The black variety had higher tolerance index, and sustained to express higher activity of antioxidative enzymes at a particular concentration nickel as compared to white variety.