Selenium and sulfur increase sulfur uptake and regulate glucosinolate metabolism in Brassica oleracea

Selenium in soils can result in increased uptake of S and a reduction in glucosinolates in Brassica species. Rapid cycling B. oleracea plants were grown hydroponically in nutrient solution with Se treatments delivered as sodium selenate in concentrations of 0.0, 0.5, 0.75, 1.0 and 1.5 ppm. Elevated S treatments of 37 ppm sulfate and 37 ppm sulfate/0.75 ppm selenate were incorporated to compare with Se treatments. Se concentration in the nutrient solution was positively correlated with Se and S uptake in the plants. The S concentration of plants exposed to Se was equal to or greater than the S concentration of plants exposed to elevated S in the nutrient solution. In spite of higher S concentrations, there was a decrease in production of 5 of the 7 glucosinolates analyzed in Se enriched plants. Plants in elevated S treatments had higher glucosinolate production than Se treated plants. These results suggest that Se either up-regulates or prevents the down-regulation of S uptake in B. oleracea. In addition, Se's presence within the plant seems to have a negative impact on the production of certain glucosinolates despite adequate availability of S.