Selenium Biofortification of Mustard Microgreens Combined with LED Lighting

Selenium (Se) biofortification may increase the nutritional value of microgreens, but its effects on growth and phytochemical composition can depend on the lighting environment. This study compared three commercially available white LED lighting regimes to evaluate the responses of hydroponically grown mustard microgreens (Brassica juncea L. ‘Red Lace’) to Se supplementation. A factorial experiment combined nominal correlated colour temperatures of 3000, 3500 and 4000 K with Se-free nutrient solution or 2 mg Se L−1 supplied as sodium selenate. Plants received a photosynthetic photon flux density of 220 μmol m−2 s−1 under an 18 h photoperiod and were harvested 10 days after sowing at the cotyledon stage. Growth responses depended on the lighting treatment: Se reduced all four measured biomass traits at 4000 K, whereas no significant differences from the matched Se-free control were detected at 3500 K. The 3500 K treatment produced the highest shoot Se concentration among Se-supplemented plants. Under this lighting setting, Se increased the summed α- and β-carotene concentrations, chlorophyll b and the sum of measured phenolic compounds, together with ABTS and FRAP responses, but decreased DPPH, APX, SOD and GR values. The responses therefore indicate trait-specific changes rather than a uniform improvement in antioxidant protection. The highest shoot fresh weight occurred at 4000 K without Se. These findings identify a promising tested combination for shoot Se enrichment and selected phytochemical traits, while showing that biomass and antioxidant-related objectives require separate evaluation.