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

Phytochelatin has been quantified in Thalassiosira weissflogii, a mari ne 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 e nvironment. Within the range of concentrations relevant to natural wat ers, Cd, and to a lesser extent Cu and Zn, are the most effective indu cers of phytochelatins. The generality of this result was confirmed by short-term experiments with two other phytoplankton species. Quantifi cation of intracellular Cd, Ni, and Zn shows that phytochelatin produc tion 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.