Toxicity and Translocation of Selenium in Phaseolus vulgaris L

Selenium (Se) is not considered an essential nutrient for plants, although trace amounts of this element can enhance the growth and yield of some plant species. The application of sodium selenate in staple foods has been proposed as an alternative to minimize Se deficiency in the human diet. However, the threshold between deficiency and toxicity for Se is very narrow. Different plant species vary considerably in the absorption and accumulation of Se in shoots and other edible parts, and also in the tolerance to high Se concentrations in the soil. Therefore, this study aimed to evaluate the Se toxicity in common bean plants grown under high doses of sodium selenate, and the Se translocation of contaminated bean seeds to next generation grains. The study was carried out on a field experiment with the application of four rates of sodium selenate (0, 50, 500 and 5000 g/ha) to the soil were common bean crop was grown. Following, greenhouse conditions were used to investigate the translocation of Se from enriched seeds to the grains. The common bean showed tolerance to sodium selenate rates up to 500 g/ha, with reduction of yield observed at rate of 5000 g/ha. Even with no symptoms of toxicity the application rates of 500 g/ha of sodium selenate to the soil produced grains with concentrations of Se that surpass the limit established by Brazilian food law. The seeds enriched with Se can translocate this nutrient to the next generation.