THE INFLUENCE OF CD, PB, CU AND NI ON NO3- UPTAKE BY CUCUMBER SEEDLINGS .2. IN-VITRO AND IN-VIVO EFFECTS OF CD, CU, PB AND NI ON THE PLASMALEMMA ATPASE AND OXIDOREDUCTASE FROM CUCUMBER SEEDLINGS ROOTS

Cd, Cu, Pb and Ni applied in vitro in concentrations which inhibited t he nitrate absorption decreased a vanadate-sensitive ATPase activity. The highest inhibition of this activity was observed in the case of Cu -treatment (55%) and the lowest one was observed for Ni-treatment (12% ). Tested metals in vitro experiments markedly decreased also NADH-fer ricyanide oxidoreductase. However in vivo they have no effect on this activity. In vivo application of metals for 24 h resulted in a stimula tion of H+-ATPase activity by Ni and its inhibition by Cu. Cd and Pb i n vivo did not change the activity of an enzyme as compared to the con trol. Similarities in the rate and degree of inhibition as well ATPase , as oxidoreductase and NO3- uptake by heavy metals in in vitro experi ments indicate that these enzymes may be a first targets of heavy meta ls action causing the decrease in NO3- absorption.