ACCUMULATION OF SELENO-AMINO ACIDS IN LEGUME AND GRASS PLANT-SPECIES GROWN IN SELENIUM-LADEN SOILS

Seleno-amino acid accumulation was studied for two legume and two gras s species grown in Selenium (Se)-laden soils. An antagonistic relation ship was found between the tissue Se-amino acid concentration and the corresponding sulfur-amino acid concentration. This relationship demon strates a competitive interaction between Se and sulfate at the amino acid synthesis level. The nonsulfur-containing amino acids were not su bstantially affected by the increase of tissue Se concentration. Sour clover (Melilotus indica L.) was able to accumulate much greater tissu e Se concentration than the other three species. Tissue methionine con centration of sour clover, rabbitfoot grass (Polypogon monspeliensis L .), and tall fescue (Festuca arundinacea Schreb.) was not significantl y affected by the increase of tissue selenomethionine concentration, b ut a highly significant negative correlation was found in alfalfa (Med icago sativa L.). This discrepancy suggests that a less antagonistic e ffect on sulfur-amino acids under the increase of Se-amino acid analog ues in the tissue might be able to minimize Se toxicity to the plant. Both Se-methylselenocysteine (nonprotein amino acid) and selenomethion ine (protein amino acid) accumulated in the plants when grown in Se-la den soils. Possible effects of these Se-amino acids accumulated by pla nts on animal health should be tested before the plants are used for f orage supplementation.