Excretion of ions (Cd²⁺, Li⁺, Na⁺ and Cl⁻) by <i>Tamarix aphylla</i>

Abstract

Excretion of minerals by the NaCl‐resistant and comparatively cadmium‐resistant tree Tamarix aphylla (L.) Karst, was investigated. Cd 2+ was excreted by plants exposed for 1–10 days to 9 or 45 μ M Cd 2+ solutions. Excretion of this toxic ion increased considerably with time but was less than 5% of the quantities that had been accumulated in the shoots. Excretion of Na + and Cl − was positively correlated with NaCl concentration (1.5, 10, 50 m M ) of the medium. The Na + /Cl − ratios of the excrete were positively correlated with the concentration of the treatment solution. Ca 2+ excretion decreased with increasing NaCl concentrations of the solution. Excretion of K + and Mg 2+ was only little affected by NaCl. Excretion of Li + occurred whenever this element was supplied in the uptake solution; daily excretion rates of Li + increased with time. The ecological significance of excretion is discussed in relation to the low selectivity of the mechanism in T. aphylla .