PHYTOCHELATIN PRODUCTION IN MARINE-ALGAE .2. INDUCTION BY VARIOUS METALS

Phytochelatin has been quantified in Thalassiosira weissflogii, a marine diatom after exposure to a series of trace metals (Cd, Pb, Ni, Cu, Zn, Co, Ag, and Hg) at concentrations similar to those in the marine environment. Within the range of concentrations relevant to natural waters, Cd, and to a lesser extent Cu and Zn, are the most effective inducers of phytochelatins. The generality of this result was confirmed by short-term experiments with two other phytoplankton species. Quantification of intracellular Cd, Ni, and Zn shows that phytochelatin production does not follow a simple stoichiometric relationship to the metal quotas. The rapid formation of phytochelatin in T. weissflogii after Cd exposure and the fast elimination when metal exposure is alleviated reveal a dynamic pool of phytochelatin which is tightly regulated by the cell.