The effect of heavy metal ions (Ni2+, Zn2+, Cu2+, Pb2+) in concentrations of 10 ?M, 0.1 ?M and 1 mM on the rate of lipid peroxidation (LPO) has been studied in the 7-day-old seedlings of cucumber (Cucumis sativus L.) and radish (Raphanus sativus L.). It was revealed that Ni2+ and Cu2+ ions induced oxidative stress in plant cells, but Pb2+ and Zn2+ ions did not have toxic effects. The heavy metals effect on LPO increasing was as follows: Zn2+ < Pb2+< Ni2+ < Cu2+ for cucumber plants; Pb2+< Zn2+ < Cu2+ < Ni2+ for radish plants.
