Bioconcentration and phytotoxicity of Cd in Eichhornia crassipes.

Plants of Eichhornia crassipes grown at various levels of cadmium ranging from 0.1 to 100 microg ml(-1) accumulated Cd in a concentration and duration dependent manner. At all levels, Cd accumulation by various plant tissues followed the order roots shoot leaves. Approximately 80% of total Cd was accumulated by plant at highest concentration (100 microg ml(-1)) used in the experiment. Cadmium induced phytotoxicity appears at 25.0 microg ml(-1) resulting into reduced levels of chlorophyll, protein and in vivo nitrate reductase activity of the plant. However, a slight induction of these physiological variables was obtained at lowest Cd (0.1 microg ml(-1)) concentration. In contrast, carotenoid content increased at highest Cd concentration i.e., 100 microg ml(-1). Similar effects at low and high levels of Cd was obtained with respect to mitotic index and micronuclei in root meristem of the plant. It could be inferred that Cd toxicity in plant is differential depending upon the low and high concentration of Cd in the medium.