ABSTRACT
Selenium (Se) is a nonmetallic element in Group VIa of the periodic table, between sulfur and tellurium, and with properties like both. It is an essential element for most animals in low concentrations, although it is toxic at higher concentrations. It was claimed to be benecial for the growth of some plants in the 1920s and 1930s and even to be possibly essential (Hewitt, 1966). Levine (1925) showed that selenium inhibited the germination and growth of white lupin (Lupinus alba L.) and timothy grass (Phleum pratense L.), but at low concentration (0.0001% and 0.001%), selenous acid and selenic acid stimulated the growth of the lupin plants. Some indication of benecial effects of Se on plant growth had been published by Stoklasa (1922). Trelease and Trelease (1938) knew it could accumulate in high enough concentrations in plants to be toxic to animals and that some plants (including species of Astragalus, Stanleya, Xylorhiza, and Oonopsis in three different plant families) accumulated Se at concentrations of up to several thousand ppm if grown in seleniferous soils. Some of these species could be considered indicator plants of high soil Se concentrations.
