Lead Tolerance in Sesbania drummondii

Sesbania drummondii, a Fabaceous shrub of the Southeastern United States, is a hyperaccumulator of lead. Studies have indicated that lead and other heavy metals are toxic to plants and trigger both disturbances in photosynthetic activity and oxidative stress reactions in plant cells. Oxidative stress reactions are correlated with activities of antioxidative enzymes such as catalase and superoxide dismutase. In the present experiment, activities of catalase and superoxide dismutase in plants treated with 500mg/L Pb(NO3) 2 in combination with various concentrations of EDTA, HEDTA and DTPA was determined at 0, 7, 14, 21 and 28 days. Activities of these enzymes in plants exposed to Pb did not show any significant change with respect to controls. Further studies will be necessary in order to completely discern the effect of Pb on activation of antioxidative reactions. Growth parameters of Pb-exposed plants were also studied. No significant change was observed. These results indicate that Sesbania drummondii has some mechanism to counteract the toxic effects of lead, and thus hyperaccumulates Pb while not affecting antioxidant enzymatic activity. Further evidence of the lead tolerance of Sesbania drummondii will be presented. Pb uptake of plants grown in soil containing 0-15,000 ppm Pb(NO3) will be determined and presented