Biofortification for Radish and Pea Microgreens in Plant Factory: Effects of Different Selenium Concentrations in Nutrient Solution

Selenium (Se) is an essential micronutrient for human health and a beneficial element participating in multiple biological functions in plants.Microgreens, which have short growth cycles but high productivity, are ideal candidates for Se biofortification in plant factory.However, the optional dosage of exogenous Se application and the mechanisms of selenite uptake and conversion in microgreens remain unclear.This study investigated the effects of exogenous sodium selenite concentrations (0 -55 µM) in nutrient solution on plant growth and Se metabolisms in radish and pea microgreens.We found that the total and organic Se contents in plants reached maximum at 35 µM treatment in radish microgreens and reached a plateau at 25-55 µM treatment in pea microgreens.However, 45 -55 µM Se significantly reduced fresh weight and plant height compared to lower Se concentrations.35 µM Se enhanced the contents of reduced glutathione and selenocysteine methyltransferase (SMT) in radish and the contents of ATP sulfurylase, cysteine synthase and SMT in Pea, compared to other Se concentrations, which increases the concentrations of SeCys, SeMet, MeSeCys in radish microgreens and SeCys in pea microgreens.Furthermore, radish microgreen had higher total Se and organic Se concentrations compared to pea microgreen, making radish a more suitable microgreen for Se-enriched production.To conclude, we confirmed that the biofortification of microgreens with appropriate Se concentrations is feasible, and an exogenous Se application of 35 µM in nutrient solution would be optional to maintain normal plant growth but enhancing Se accumulation and translocation to shoot in radish and pea microgreens.