Plant Accumulation of Sulfur’s Sister Element Selenium – Potential Applications and Ecological Implications

Abstract

Selenium (Se) is an essential nutrient for many organisms including humans, but is also toxic at higher levels. Both Se deficiency and Se toxicity are problems worldwide. Although Se has not been shown to be essential for higher plants, it is considered a beneficial element, providing enhanced antioxidant activity. Selenium is chemically similar to sulfur (S) and readily taken up and assimilated via sulfur (S) transporters and enzymes. Thus, Se can replace S in many S compounds, including volatile forms. Some plants native to Se-rich soils can hyperaccumulate Se to levels around 1% of plant dry weight. They grow poorly without Se and thus appear to profit from Se physiologically. Selenium can also serve ecological functions as an elemental defense against pathogens and herbivores, and in elemental allelopathy. The ability of plants to (hyper)accumulate and volatilize Se may be used for phytoremediation of polluted soils or waters, and also to produce nutritionally enhanced crops. These applications will benefit from better insight into the mechanisms that control Se tolerance and accumulation in plants, and the potential ecological implications. This review gives an overview of our current knowledge of plant Se metabolism, including Se tolerance and hyperaccumulation mechanisms. It also summarizes what is known about ecological implications of plant Se (hyper)accumulation.