Selenite uptake by Medicago sativa L. roots

Abstract

This study aimed to examine selenite uptake in Medicago sativa L. Potted alfalfa plants were grown in sterilized quartz sand and exposed to 1 and 10 μM selenite for 21 days. Thirty-day-old seedlings and excised roots were used to determine the mechanism of selenite uptake in alfalfa. The following patterns of Selenium (Se) distribution in roots were as follows: lateral roots > taproots and subcellular fraction (I) > fraction (III) > fraction (II). With increasing pH, Se uptake in roots decreased markedly. The dose-dependent Se net uptake at pH 5.5 followed the Michaelis–Menten kinetics. Addition of phosphate decreased Se uptake in the excised roots (P < 0.05), whereas a deficiency in phosphate increased Se uptake (P < 0.05). The results indicate that alfalfa mainly absorbed selenium through lateral roots. Selenite uptake by alfalfa root depended on pH, with the preferential form absorption of as H₂SeO₃ > HSeO₃¹⁻ > SeO₃²⁻. A portion of selenite was absorbed actively and may be mediated by phosphate transporter.