Manipulation of light intensity and spectrum for driving growth and metabolism to improve nutritional and nutraceutical quality of microgreens

Microgreens, young edible seedlings of many plant species, harvested just a few weeks after germination, are increasingly valued for their high nutritional and nutraceutical properties. As interest in functional food and sustainable urban farming has been increased in the last years, optimizing microgreen production under controlled environment has become a key research topic. Light, as intensity, spectral composition and photoperiod, is one of the most influential factors in regulating plant growth and promoting bioactive compounds accumulation. Nowadays, light emitting diodes (LEDs) allows the precise control of these parameters of artificial light, making possible to steer plant metabolism and enhance the produce quality. This review explores how light intensity and spectrum influence growth, morphology, and secondary metabolism in microgreens, with special focus to the biosynthesis of healthy phytochemicals, including antioxidants like vitamins, phenolics, flavonoids, and glucosinolates. In general, among the reviewed studies, moderate intensities and balanced blue red spectra or ratios with a higher proportion of blue (B) respect to red (R) resulted in the highest biomass accumulation making R50:B50 or B70:R30 the most efficient spectra for microgreens production. Selective enrichment of specific wavelengths enhances secondary metabolism, particularly functional compounds.