Selenium Assimilation and Nutrient Element Uptake in White Clover and Tall Fescue under the Influence of Sulphate Concentration and Selenium Tolerance of the Plants

Abstract

Tall fescue (Festuca arundinacea Schreb.) and white clover (Trifolium repens L.) were examined for Se assimilation and nutrient element uptake. Substantial Se tolerance difference was found between the two species. An inverse relationship between Se accumulation and Se tolerance suggests an exclusion mechanism that restricts Se uptake by the plant with greater Se tolerance. A positive relationship between the increase of protein Se concentration and growth inhibition in the plants suggests that assimilation of Se into proteins is responsible for the Se toxic effect and this study indicates that the antagonistic effect of sulphate is responsible for reducing Se toxicity at the protein level. No evidence that a Se exclusion mechanism which excludes Se from incorporating into protein, such as that found in Astragalus species, plays any major role of Se tolerance in these two species. Under Se treatment, plant tissue Ca concentration was increased, but P concentration was decreased. A higher Fe concentration was found in white clover which increased with increasing tissue Se concentration. Copper, Mn, and Zn concentrations only increased in the white clover under conditions of severe growth inhibition.