Selenium and its species in the environment | Selen in njegove zvrsti v okolju
Znidarcic, D., Ljubljana Univ. (Slovenia). Biotechnical Fac., Agronomy Dept.
Selenium (Se) is an essential element for humans and animals, but there is no evidence if plants need it. Moreover, several studies have suggested that some organic forms of Se could show anticarcinogenic properties against certain types of cancer. Se is present in soil (naturally or due to anthropogenic activities) and can enter the food chain through plants. In environmental samples, Se can be found in inorganic and organic forms, including selenoaminoacids and metylathed compounds. The ability of several plants to accumulate and transform inorganic forms of Se into bioactive organic compounds has important implications for human nutrition and health. Se essentiality for plants has not yet been proven, but many plants are capable of accumulating higher concentratios of Se compounds. Certain native plants (as species of Astragalus, Stanleya, Morinda and Neptunia) are able to accumulate several thousand milligrams of Se kg-1 dry weight in their tissues (Se accumulators). On the other hand, most crop plants contain less than 25 mg Se kg-1 dry weight (Se nonaccumulators). A third category of plants (Aster, Atriplex, Castilleja _), grown on soils of low-to-medium Se content and accumulate up to 1,000 mg Se kg-1 dry weight (secondary Se accumulators). The resistance to excessive Se has been related to the formation of organoselenium compounds (SeCys and SeMet) that can not be incorporated into proteins and also the ability of these plants to convert Se into volatile species.
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