THE SHORT-TERM UPTAKE OF ZINC AND CELL MORTALITY OF THE SEAGRASS HALOPHILA-STIPULACEA (FORSK) ASCHERS

Zinc uptake in the upper (leaves) and lower ground parts (roots, stems , rhizoids) of Halophila stipulacea (Forsk.) Aschers. and leaf cell mo rtality were examined in laboratory experiments. The seagrass was incu bated for 12 days in zinc concentrations between 10(-4) and 10(-7) M. At 10(-6) and 10(-7) MZn concentrations, uptake was characterized by a rapid initial adsorption rate slowly decreasing up to the 4th day, af ter which an equilibrium was reached; the 'equilibrium' concentrations increased as the Zn in seawater increased. At the higher Zn concentra tions (10(-5) and 10(-4) M) the content in the plant continued to incr ease after the 4th day, perhaps due to the development of necrotic eff ects mainly evident in the teeth and epidermal cells as well as in the mesophyll cells of the leaves. A positive correlation between Zn cont ent in the upper and lower parts of H. stipulacea was also found, wher eas Zn uptake in leaves was significantly higher than in the root-rhiz omes-rhizoids. It was also demonstrated that some zinc can leak from t he tissues of this seagrass.