Nutrient Solution Concentrations of Na2SeO4 Affect the Accumulation of Sulfate and Selenate in Brassica oleracea L.

Dietary sources of selenium (Se) are associated with human health benefits, and Brassica species are good sources of Se in human diets. Selenium and S compete for absorption and accumulation in plant tissues; therefore, the ratios of Se to S in the growing environment determine the accumulation of selenium in plants. To determine responses for Brassica oleracea L., two levels of Na 2 SeO 4 (96 mg·L −1 SeO 4 2– and 0.384 mg·L −1 SeO 4 2– ) were added to nutrient solutions with or without MgSO 4 ·7H 2 O (96 mg·L −1 SO 4 2– ). The highest plant fresh weight and S and SO 4 2– accumulation were found when plants were grown in the medium with a SeO 4 2– to SO 4 2– ratio of 1 : 250 (0.384 mg·L −1 SeO 4 2– and 96 mg·L −1 SO 4 2– ). However, the highest accumulation of Se was found when a low level of selenate (0.384 mg·L −1 SeO 4 2– ) was added to nutrient solutions without S. The activity of glutathione peroxidase (GPx) was regulated by Se status; the highest GPx activity was measured when a high level of SeO 4 2– (96 mg·L −1 ) was supplied to nutrient solutions without S supplementation. The lowest concentration of total glucosinolates was found when adding SeO 4 2– to nutrient solutions without S. We saw no difference in plant growth and mineral accumulation when plants were grown with K 2 SeO 4 versus Na 2 SeO 4 , suggesting that the growth-inhibiting effect of Na 2 SeO 4 was the result of the SeO 4 2– rather than potentially toxic effects of Na + .