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

Abstract

Zinc uptake in the upper (leaves) and lower ground parts (roots, stems, rhizoids) of Halophila stipulacea (Forsk.) Aschers, and leaf cell mortality were examined in laboratory experiments. The seagrass was incubated for 12 days in zinc concentrations between 10−4 and 10−7 M. At 10−6 and 10−7 M Zn concentrations, uptake was characterized by a rapid initial adsorption rate slowly decreasing up to the 4th day, after which an equilibrium was reached; the ‘equilibrium’ concentrations increased as the Zn in sea water increased. At the higher Zn concentrations (10−5 and 10−4M)the content in the plant continued to increase after the 4th day, perhaps due to the development of necrotic effects mainly evident in the teeth and epidermal cells as well as in the mesophyll cells of the leaves. A positive correlation between Zn content in the upper and lower parts of H. stipulacea was also found, whereas Zn uptake in leaves was significantly higher than in the root-rhizomes-rhizoids. It was also demonstrated that some zinc can leak from the tissues of this seagrass.