Role of glutathione and phytochelatin in Hydrilla verticillata (I.f.) royle and Valusneria spiraus L. under mercury stress

Both free (Hydrilla verticillata) and rooted (Vallisneria spiralis) submerged plants showed high potential to accumulate mercury, maximum being in roots of V. spiralis. During mercury stress these plants synthesized different species of phytochelatins (PCs), which bind with the accumulated mercury and showed high levels of cysteine and non-protein thiols. The induction of phytochelatins was accompanied by a decline in cellular levels of glutathione in both the plants, although the decline was only observed at high concentration and long duration of Hg in V. spiralis. Buthionine sulfoximine inhibited accumulation of non-protein thiols and glutathione, indicating the involvement of glutathione in phytochelatin synthesis. However, cycloheximide had no effect on early PC synthesis. Results showed that phytochelatins are synthesized in these plants and play a role in mercury detoxification.