Biochemical Mode of Resistance to Environmentally Toxic Heavy Metal Lead in two Species of Alternanthera

Present study evaluated effect of toxic heavy metal lead in various biochemical parameters in plants. During the exposure of plants to contaminated soils, the antioxidant defense system helps the plant to protect itself from the damage. Greenhouse experiment was conducted and consisted of range finding test and definitive test for various concentrations of heavy metal lead. The bioorganics of the plant such as soluble sugar, protein, lipid, phenol, amino acid photosynthetic pigments and antioxidant enzymes were estimated after 30 days of treatment. The activity of enzymatic antioxidants such as superoxide dismutase (SOD; E.C. 1.15.1.1), catalase (CAT: EC 1.11.1.6), polyphenol oxidase (PPO; EC 1.14.18.1) and peroxidase (POX; E.C. 1.11.1.7) showed profound variations in response to Pb stress from the control plants. It was found that Pb induced oxidative stress in both the species of Alternanthera, enhance antioxidant enzyme activities and antioxidant concentrations. Non enzymatic antioxidants such as proline and phenol increased with Pb concentration. Chlorophyll content seemed to be reduced with Pb concentration. Both species of Alternanthera showed tolerance against Pb induced stress and can be suggested as a suitable candidate for phytoremediation of Pb.