ASHS 2025 Conference

With growing consumer interest in health-promoting diets, microgreens have gained importance as nutrient-rich and functional leafy greens. These crops are increasingly grown indoors under LED lighting and the manipulation of light quality has been identified as a critical factor influencing plant growth, yield, and nutritional quality. Blue and red LED are both considered critical for plant growth, have high photon efficiency and can be readily absorbed and utilized by plants. However, each wavelength has different effects on the plant physiology and metabolism and there is a need to understand how their combination in different proportions may affect microgreens yield, morphology and nutritional quality. Therefore, we conducted a study aimed at evaluating the effects of different combinations of blue and red LED light on the yield and nutritional composition of radish and broccoli microgreens. Microgreens were grown in a walk-in growth chamber under a 14-hour photoperiod and six LED treatments (%): 100 white, 100 red, 100 blue, and blue: red ratios of 50:50, 25:75, and 75:25. The average photosynthetic photon flux density was 165 μmol m−2 s−1. Radish and broccoli were harvested after 7 and 8 days, respectively. Microgreens grown under 100% blue, red, and white LED light showed higher shoot height than those grown under mixed blue:red treatments, with 100% blue producing the tallest shoots. Dry biomass accumulation differed among treatments, with 100% blue LED light resulting in the lowest dry biomass. At the phytochemical level, antioxidant activity showed to be highest under 100% blue light, with a 16.3% increase across both species, while 100% red resulted in the lowest levels. The mineral composition was also affected by LED treatments, as microgreens grown under blue: red 50:50, 25:75, and 75:25 treatments resulted in the highest iron concentrations, averaging 10.4% higher compared to monochromatic red and blue light or to broad-spectrum white light. These findings are consistent with previous studies indicating that blue light enhances secondary metabolite accumulation and that combined red and blue light influences mineral uptake, highlighting the importance of light optimization for the commercial quality of microgreens grown in controlled environment.