THE ROLE OF CALCIUM IN INTRACELLULAR CADMIUM UPTAKE BY THE LICHEN PELTIGERA-MEMBRANACEA

The possible role of calcium in the intracellular uptake of cadmium by the lichen Peltigera membranacea was investigated. Even when calcium was removed from extracellular sites by potassium pretreatment, kinetic studies failed to provide evidence in support of added calcium being a competitive inhibitor of cadmium uptake. Calcium and cadmium uptake responded differently to the presence of lanthanum, vanadate or verapamil. Except for the effect of verapamil, intracellular uptake of cadmium mostly reflected the quantity of cadmium bound to extracellular exchange sites. © 1993 Annals of Botany Company.