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Light quality: growth and nutritional value of microgreens under indoor and greenhouse conditions

Brazaityte, A., Virsile, A., Samuoliene, G., Jankauskiene, J., Sakalauskiene, S., Sirtautas, R., Novickovas, A., Dabasinskas, L., Vastakaite, V., Miliauskiene, J., Duchovskis, P.
Acta horticulturae 2016 no.1134 pp. 277-284
Brassica rapa subsp. chinensis, antioxidants, basil, beets, greenhouses, growth chambers, harvest date, lamps, light quality, microgreens, nitrate reduction, nutritive value, parsley, secondary metabolites, sodium, ultraviolet radiation, wavelengths
The objective of our studies was to determine the growth and nutritional value of microgreens cultivated under light-emitting diode (LEDs) lamps of various spectral compositions. We have performed several experiments in growth chambers and in a greenhouse. A system of high-power solid-state lighting modules with the main set of 447-, 638-, 665- and 731-nm LEDs with the possibility to use supplemental 366-, 390-, 402-, 520-, 595-, 622-nm LEDs was used in indoors experiments. High-pressure sodium (HPS) lamps supplemented by 390- and 638-nm LEDs were used for experiments in a greenhouse. Microgreens of 6 species (mustard, red pak choi, tatsoi, basil, beet and parsley) were grown up to harvest time (about 7-10 d). The experiments indoors revealed that supplemental 520- and 622-nm lighting was more efficient for nitrate reduction, while the antioxidative system indices were enhanced by 595-nm diodes. Positive effect of UV-A radiation for antioxidant compounds was determined, but such effect on growth parameters was insignificant. Supplemental 366- and 390-nm UV-A radiation have been more favourable for antioxidant accumulation. Short-term (3-days before harvesting) lighting with high PPFD level of red (638 nm) LEDs increased the amounts of the secondary metabolites of microgreens under both cultivation conditions. Studies showed that various LEDs illumination could be a good tool for investigating the impact of specific wavelengths on nutritional value compounds in microgreens.