STUDIES OF UPTAKE AND TOXIC EFFECTS OF CR(VI) ON PISTIA-STRATIOTES

The uptake of Cr(VI) and toxic effects of the metal on some biochemical parameters in Pistia stratiotes L. were studied. The uptake of Cr(VI) by the plants gradually increased with increase in concentration of Cr(VI) in the culture medium. Maximum accumulation of Cr(VI) was noted within 5 days. Maximum removal (about 90%) of Cr(VI) was recorded below 5 ppm. Accumulation of Cr(VI) occurred mainly in roots. At 5 and 10 ppm, Cr(VI) promoted senescence of Pistia plants by decreasing chlorophylls, protein, RNA, Hill activity and activities of catalase, protease as well as increasing dry weight, free amino acid content, peroxidase activity and ratio of acid to alkaline pyrophosphatase activity over control values. At Cr(VI) concentrations below 5 ppm, these constituents were least affected. So, Pistia plants can be utilized as the scavenger of Cr(VI) from waste water.