EFFECT OF CD ON PLASMA-MEMBRANE ATPASE FROM PLANT-ROOTS DIFFERING IN TOLERANCE TO CD

The effect of Cd on a H+/K+ antiport in bean was determined and the ef fect of Cd on the activity of the plasma membrane ATPase partially pur ified from the roots of plants differing in tolerance to Cd2+ using an aqueous polymer two-phase system was compared. Cadmium inhibited the H+/K+ antiport in vivo and inhibited the plasma membrane ATPase in vit r. The order of Cd tolerance of the plasma membrane ATPase partially p urified from the roots was as follows: rape > pumpkin > pea > rice > k idney bean in the treatment at 10-50 mu M Cd. Cadmium tolerance of ATP ase appeared to be positively correlated with Cd tolerance in intact p lants, except in rice. The results suggested that Cd may be associated with many components in the plasma membrane and may affect ion transp ort and that the Cd tolerance of ATPase may be one of the mechanisms o f Cd tolerance in intact plants.