Sunflower seedlings hyperaccumulate Selenium.

Selenium (Se) is an essential element for animals and humans, but not plants. However, the capacity of some plants to accumulate and transform Se into bioactive compounds has important implications for human nutrition and health. In this study, sunflower (Helianthus annuus) and maize (Zea mays) seedlings were cultivated in soil to investigate the effect of different rates of sodium selenite (1-90 mg kg^-1 soil) and sodium selenate (1-30 mg kg^-1 soil) on absorption and translocation of Se and sulphur (S). Sodium selenate decreased growth of sunflower roots at all applied rates and of maize roots at the highest rate applied. In contrast, sodium selenite up to 30 mg kg^-1 for sunflower and 3 mg kg^-1 for maize resulted in increased shoot and root growth. An increase in Se concentration in soil resulted in an increase in Se and a decrease in S accumulation in roots and shoots of both maize and sunflower. Selenium translocation from roots to shoot was higher in sunflower than maize. Root-to-shoot translocation of Se was 5 to 30 times greater in sunflower and 0.4 to 3 times greater in maize in the sodium selenate than sodium selenite treatments. Sunflower, as a Se-hyperaccumulator with up to 1.8 g kg^-1 in shoots (with no significant decrease in shoot biomass) can be a valuable plant in biofortification to improve animal/human nutrition, as well as in phytoremediation of contaminated sites to restore ecosystem services.