Cellular distribution of copper, lead and zinc in the grey mangrove, Avicennia marina (Forsk.) Vierh

• Published in: Aquatic botany Vol. 68; no. 1; pp. 45 - 59
• Main Authors: MacFarlane, G.R, Burchett, M.D
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2000
• Subjects: Avicennia marina; Bioaccumulation; Copper; Heavy metals; Lead; Mangrove; Roots; Salt glands; X-ray microanalysis; Zinc; Avicennia marina; Salt glands; X-ray microanalysis; Bioaccumulation; Mangrove; Roots; Lead; Copper; Heavy metals; Zinc
• ISSN: 0304-3770; 1879-1522
• DOI: 10.1016/S0304-3770(00)00105-4

The distribution and excretion of Cu, Pb and Zn in the root and leaf tissue of the grey mangrove, Avicennia marina was studied using scanning electron microscope (SEM) X-ray microanalysis and atomic absorption spectroscopy. SEM X-ray microanalysis of nutritive root tissue in seedlings dosed with 4 g/l Cu, Pb and Zn revealed accumulation of all metals predominantly in cell walls. The root epidermis provided a major barrier to the transport of Pb only. The endodermal casparian strip was shown to provide a barrier to movement of all three metals into the stele. Washings from mature leaves contained significantly higher amounts of Zn and Cu than control plants after 1 month, suggesting excretion of both metals from the glandular trichomes. In addition, salt crystals exuded from the glands on the adaxial surface of mature leaves were composed of alkaline metals: Zn in Zn-treated plants, and Cu in Cu-treated plants. Leaf tissue in seedlings dosed with 4 g/l Zn showed a decreasing gradient of the metal from xylem tissue, through photosynthetic mesophyll, to hypodermal (water) tissue, with a subsequent increase in concentration in the glandular tissue. A similar gradient was observed across leaf tissue in seedlings dosed with 4 g/l Cu, however, there was no subsequent increase in Cu concentration in glandular tissue. For both metals leaf cell wall metal concentrations were consistently higher than intracellular concentrations.