Selenium nutrition of green plants. Effect of selenite supply on growth and selenium content of alfalfa and subterranean clover.

Alfalfa and subterranean clover plants were grown in highly purified nutrient solutions to which selenite selenium had been added at 0, 0.025, 0.25, 2.5 or 25.0 mug-atoms/liter. In both species, yields of tops and roots were significantly less at 25.0 mug-atoms/liter than at lower selenium concentrations (p < 0.01). The results indicated that growth was adversely affected when the concentration of selenium in mature leaf tissue reached 0.2 to 0.8 mug-atom/g dry weight.No beneficial effect of selenium was demonstrated on the growth of either species. If selenium is required by these species, the critical level will probably be below 0.001 mug-atom/g of dry plant material. Results are discussed in relation to earlier work on the selenium nutrition of plants.