INDUCTION OF PHYTOCHELATINS UNDER CADMIUM STRESS IN WATER LETTUCE (PISTIA-STRATIOTES L)

Plants of Pistia stratiotes L. accumulated appreciable amounts of Cd f rom aqueous solution, maximum being in roots than leaves. Accumulation was concentration - duration dependent, however, plant reached metal steady state concentration on 7 d at 10.0 mu M ed. The accumulation of Cd was accompanied by a decline in cellular levels of glutathione whi ch was more evident in roots at different treatment durations. Both th e concentrations of Cd (2.5 and 10.0 mu M) enhanced cysteine content, accumulation of acid-soluble thiols and induced synthesis of phytochel atins (PCs). On the other hand, lower concentration induced synthesis of low molecular weight proteins, while higher Cd concentration comple tely inhibited low molecular weight proteins and reduced concentration s of other high molecular weight proteins in the SDS-Gel electrophoret ic patterns. Buthionine sulfoximine, an inhibitor of glutathione synth esis, reduced glutathione and acid-soluble thiols. However, protein sy nthetic inhibitor cycloheximide did not affect initial production of a cid-soluble thiols showing the participation of phytochelatins in tole rance mechanism of the plant to Cd.