UPTAKE OF ZN, CR AND CD BY WATER HYACINTHS

Studies were conducted in a greenhouse to determine the phytotoxic effect and uptake capacity of Zn, Cr and Cd by the water hyacinth Eichhornia crassipes. Results show that among the three elements tested, Cd was the most phytotoxic, showing up some necrosis in the plant when the concentration was greater than 2.5 ppm. In the case of Cr and Zn, the phytotoxicity produced the appearance of chlorosis in the aerial part of the plant. For the tested rates of Cr (maximum 9 ppm) no reduction of productivity was found, whereas in the case of Zn the concentration of 9 ppm in solution caused a 30% reduction in the weight. As for the heavy metal absorption, it was proved that after 24 days of growth, the heavy metals were totally depleted from the nutritive solution suggesting complete absorption of these metals by the plants.