THE INFLUENCE OF CD, PB, CU AND NI ON NO3- UPTAKE BY CUCUMBER SEEDLINGS .1. NITRATE UPTAKE AND RESPIRATION OF CUCUMBER SEEDLINGS ROOTS TREATED WITH CD, PB, CU AND NI

Nitrate uptake by cucumber seedlings was decreased after 24 hours pret reatment of seedlings with 10 muM Cd, Cu, Ni and 50 muM Pb. However, m etals in above concentrations did not change the intensity of root res piration. Direct inclusion of metals to the uptake solution in 10-fold higher concentrations inhibited the nitrate uptake about 40-60%. This inhibition was already observed after one hour of plant exposure to t he uptake solution containing metals. The respiration of cucumber root s during one hour of tissue incubation with heavy metals in concentrat ions inhibiting NO3- absorption was similar as in the control. The res ults indicate that decrease in nitrate uptake by seedlings exposed to Cd, Cu, Ni or Pb was not due to the influence of these metals on respi ratory processes.