Effects of Different Light Spectra on Final Biomass Production and Nutritional Quality of Two Microgreens

To improve microgreen yield and nutritional quality, suitable light spectra can be used.Two species--amaranth (Amaranthus tricolor L.) and turnip greens (Brassica rapa L. subsp. oleifera (DC.)Metzg)--were studied. The experiment was performed in a controlled LED environment growthchamber (day/night temperatures of 24 ± 2oC, 16 h photoperiod, and 50/60% relative humidity).Three emission wavelengths of a light-emitting diode (LED) were adopted for microgreen lighting:(1) white LED (W); (2) blue LED (B), and (3) red LED (R); the photosynthetic photon flux densitieswere 200 ± 5 µmol for all light spectra. The response to light spectra was often species-specific, andthe interaction effects were significant. Morphobiometric parameters were influenced by species,light, and their interaction; at harvest, in both species, the fresh weight was significantly greaterunder B. In amaranth, Chl a was maximized in B, whereas it did not change with light in turnipgreens. Sugar content varied with the species but not with the light spectra. Nitrate content of shootsgreatly varied with the species; in amaranth, more nitrates were measured in R, while no differencein turnip greens was registered for the light spectrum effect. Polyphenols were maximized under Bin both species, while R depressed the polyphenol content in amaranth.