Urea and heavy metals (Ni 2+ and Cu 2+) higher concentration influence on the photosynthetic pigments’ content, lipids peroxidation intensity and urease ferments activity in the submerged aquatic macrophyte - Egeria densa Planch. have been studied. It has been shown that addition of metals to the medium with urea tends to strengthen its toxic effect upon plants. It has been found that four-day long hatching of plants in the medium with urea and nickel lead to the oxidative stress development in Canada water weed leaves. Copper concentration equal to 100 mkmol/l appeared to be lethal for plants.