Uptake of Cd2+ and Fe2+ by excised roots of Tamarix aphylla |
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Authors: | Jürgen Hagemeyer Yoav Waisel |
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Institution: | Bielefeld Univ., Faculty of Biology, Dept of Ecology, D-4800 Bielefeld, FRG;Tel Aviv Univ., G. S. Wise Faculty of Life Sciences, Dept of Botany, Tel Aviv 69978, Israel. |
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Abstract: | The uptake of Cd2+ by excised roots of Tamarix aphylla (L.) Karst, was investigated using roots of hydroponically grown plants. The concentration isotherm of Cd2+ uptake approached saturation with a single phase hyperbola. The time course of Cd2+ absorption was generally hyperbolic, with an apparent linear section between 2 and 30 min. The temperature response varied among different temperature ranges: a Q10 of approximately 1.9 was found between 10 and 20°C, but at higher and lower temperatures Q10 values were only 1–1.3. It is concluded that Cd2+ uptake by the roots of T. aphylla at moderate temperatures is mediated by a metabolic process, combined with a passive influx component that becomes dominant at higher and lower temperatures. The distribution of the absorption sites for Cd2+ and for Fe2+ along the roots of T. aphylla was also investigated. Cadmium uptake showed no apparent pattern, whereas a distinct pattern of uptake was observed for Fe2+, with the highest rates at the root tip. Iron absorption was stimulated in the presence of nutrients, whereas that of Cd2+ was inhibited. Adsorption and absorption of Cd2+ were strongly inhibited by Ca2+ and by Mg2+, but were unaffected by Fe2+. Monovalent ions (Na+, K+, Li+) also reduced Cd2+ absorption, but to a lesser extent than Ca2+ and Mg2+. Uptake of Cd+ was reduced at lower pH of the medium. The importance of interfering cations for Cd2+ tolerance of T. aphylla is emphasized. |
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Keywords: | Cadmium calcium cation exchange concentration isotherm excised roots iron magnesium metabolic uptake Q10 Tamarix aphylla |
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