The effect of continuous lighting (CL, 24 h) and light spectrum on growth and nutritional quality of arugula (Eruca sativa), broccoli (Brassica oleracea var. italic), mizuna (Brassica rapa. var. nipposinica), and radish (Raphanus sativus var. radicula) were investigated in growth chambers under light-emitting diode (LED) and fluorescent lighting. Microgreens were grown under four combinations of two photoperiods (16 h and 24 h) providing daily light integral (DLI) of 15.6 and 23.3 mol m−2 day−1, correspondingly) with two light spectra: LED lamps and fluorescent lamps (FLU). The results show that fresh and dry weights as well as leaf mass per area and robust index of harvested arugula, broccoli, mizuna, and radish seedlings were significantly higher under CL compared to 16 h photoperiod regardless of light quality. There were no visible signs of leaf photodamage. In all CL-treated plants higher chlorophyll a/b and carotenoid-to-chlorophyll ratios were observed in all plants except mizuna. CL treatment was beneficial for anthocyanin, flavonoid, and proline accumulation. Higher activities of antioxidant enzymes (catalase, superoxide dismutase, ascorbate peroxidase, and guaiacol peroxidase) were also observed in CL-treated plants. In most cases, the effects were more pronounced under LED lighting. These results indicate that plants under mild oxidative stress induced by CL accumulated more non-enzymatic antioxidants and increased the activities of antioxidant enzymes. This added nutritional value to microgreens that are used as functional foods providing health benefits. We suggest that for arugula, broccoli, mizuna, and radish, an LED CL production strategy is possible and can have economic and nutritional benefits.

No abstract

The effect of continuous lighting applied in the end-of-production period on growth and nutritional quality of radish (Raphanus sativus var. radicula), broccoli (Brassica oleracea var. italic), mizuna (Brassica rapa. var. nipposinica) and arugula (Eruca sativa) was investigated in growth chambers under LED lighting. Microgreens were grown under 16 h photoperiod and 3 days before harvest half of plants were placed under continuous lighting conditions. Pre-harvest continuous lighting treatment increased yield, robustness index, and shorten time to harvest in radish, broccoli, mizuna and arugula microgreens. The end-of-production treatment has also led to higher content of compounds with antioxidative properties (flavonoids, proline) and increased the activity of antioxidant enzymes (CAT, APX, GPX) by inducing mild photooxidative stress. Increased antioxidative status added nutritional value to microgreens that can be used as functional foods providing health benefits. Pre-harvest treatment by continuous lighting is suggested as the practice than can allow producers to increase yield, aesthetic appeal, nutritional quality, and market value of Brassicacea microgreens.

The study was carried out to assess whether continuous lighting (CL) can be used to reduce nitrate content in Brassicaceae microgreens. Arugula (Eruca vesicaria subsp. sativa), broccoli (Brassica oleracea var. italic), mizuna (Brassica rapa var. nipposinica) and radish (Raphanus sativus var. radicula) seedlings were grown in the controlled climate chambers under 16 h or 24 h photoperiod provided by light-emitting diode (LED) or fluorescent (FLU) lamps. At the pre-harvest stage, half of microgreens were treated by CL for 3 days. The results show that nitrogen content was decreased significantly in plants grown under LED CL compared to plants grown under 16 h photoperiod. The highest decrease (by 40 %) was observed in arugula microgreens. In contrast, CL provided by FLU lamps had little effect (decrease by 11 and 6 %) on nitrate content in mizuna and broccoli and no effect in arugula and radish. Pre-harvest treatment by CL resulted in significant decrease of nitrate content in all four plant species. In conclusion, continuous LED lighting applied during microgreen cultivation or at the pre-harvest stage effectively reduces nitrate content in Brassicaceae microgreens.