PHYTOCHELATIN PRODUCTION IN MARINE-ALGAE .1. AN INTERSPECIES COMPARISON

Phytochelatins are metal-binding peptides produced enzymatically by hi gher plants, fungi, and algae in response to many metals, particularly Cd. We have studied phytochelatin production in several marine phytop lankton exposed to a range of free Cd ion concentrations. As a result of increased analytical resolution, we have found that all the species contain phytochelatin, even when there is no added Cd, and that eleva ted phytochelatin concentrations are induced by Cd, even at very low a nd environmentally relevant concentrations (as low as 10(-12) M free i on concn). In some but not all species, intracellular Cd and phytochel atin concentrations are maintained at a fixed stoichiometric ratio at high Cd concentrations. Phytochelatin production and accumulation appe ar to be regulated in a manner that varies among phytoplankton species .