The promotive effect of selenium on plant growth as triggered by ultraviolet irradiation

Selenium is known to be important in antioxidation in human and animals, but little attention has been paid to its role in higher plants, Chemically it is a photovoltaic element, and in order to study. its effects on plants, ryegrass (Lolium perenne L.) and lettuce (Lactuca sativa L.) were cultivated in a pot experiment without or with H2SeO4 (0.1 and 1.0 mg Se kg(-1)) under normal light or subjected to UV(B)irradiation episodes, Without Se addition, UV(B) diminished markedly the yield of lettuce (by 8%) but not that of ryegrass.The lon-er Se dosage had no effect on yields under normal Light conditions, but in combination with UV(B) it enhanced plant growth, This indicates that UV light acted as a trigger for the growth-promoting effect of Se. The higher Se dosage was toxic to plants, but the toxicity was alleviated under UV(B). The positive interaction between the high-energy light and Se was manifested also as increased concentrations of nucleic acids and soluble proteins. The synergistic effect was partly attributable to the antioxidative function of Se, shown as inhibition of lipid peroxidation and promotion of glutathione peroxidase (GSH-Px) activity. Some other possible mechanisms of the positive action of Se are discussed.