UPTAKE OF CADMIUM AND THE EFFECT ON VIABILITY OF LEAF-CELLS IN THE SEAGRASS HALOPHILA-STIPULACEA (FORSK) ASCHERS

The uptake of cadmium (Cd) in the leaves and lower parts of Halophila stipulacea (Forsk.) Aschers. was studied in laboratory experiments. Plants were incubated in seawater with 10(-4)-10(-9) mol L-1 Cd for 16 days. The toxicity of cadium was assessed by the leaf-cell viability test. At the lower Cd concentrations (10(-9) and 10(-8) mol L-1) all leaf-cells remained alive up to the end of the experiment. In these solutions, Cd was taken up rapidly till the 4th day, after which the tissue contents stabilized; these 'equilibrium' concentrations increased along with those in the medium. At the higher Cd levels the uptake continued after the 4th or 8th day; this may be due to cellular damage and fall of leaves in the highest solution. The mortality of the leaf-cells increased with increasing concentrations of Cd in the test solution, with increase of incubation time and in the order: 'mid-rib' > 'mesophyll' > 'epidermal' > 'teeth' cells. The leaves of H. stipulacea accumulated significantly higher Cd concentrations than the lower parts. A positive correlation was also observed between Cd contents in the two parts.