The essentiality of selenium for humans, animals, and plants, and the role of selenium in plant metabolism and physiology

After its discovery, selenium was most noted for its harmful effects. Selenium was the first element identified to occur in native vegetation at levels toxic to animals. Poisoning of animals can occur through consumption of plants containing toxic levels of selenium. Livestock consuming excessive amounts of selenized forages are afflicted with “alkali disease” and “blind staggers”. Typical symptoms of these diseases include loss of hair, deformed hooves, blindness, colic, diarrhoea, lethargy, increased heart and respiration rates, and eventually death. On the other hand, selenium deficiency in animal feeds can cause “white muscle disease”, a degenerative disease of the cardiac and skeletal muscles. In this regard, this review paper attempts to summarize the essentiality of selenium for humans, animals, and plants and the role of selenium in plant metabolism and physiology.