Light Intensity and Photoperiod Affect Growth and Nutritional Quality of Brassica Microgreens

Abstract

We explored the effects of different light intensities and photoperiods on the growth, nutritional quality and antioxidant properties of two Brassicaceae microgreens (cabbage Brassica oleracea L. and Chinese kale Brassica alboglabra Bailey). There were two experiments: (1) four photosynthetic photon flux densities (PPFD) of 30, 50, 70 or 90 μmoL·m−2·s−1 with red:blue:green = 1:1:1 light-emitting diodes (LEDs); (2) five photoperiods of 12, 14, 16, 18 or 20 h·d−1. With the increase of light intensity, the hypocotyl length of cabbage and Chinese kale microgreens shortened. PPFD of 90 μmol·m−2·s−1 was beneficial to improve the nutritional quality of cabbage microgreens, which had higher contents of chlorophyll, carotenoids, soluble sugar, soluble protein and vitamin C, as well as increased antioxidant capacity. The optimal PPFD for Chinese kale microgreens was 70 μmol·m−2·s−1. Increasing light intensity could increase the antioxidant capacity of cabbage and Chinese kale microgreens, while not significantly affecting glucosinolate (GS) content. The dry and fresh weight of cabbage and Chinese kale microgreens were maximized with a 14-h·d−1 photoperiod. The chlorophyll, carotenoid and soluble protein content in cabbage and Chinese kale microgreens were highest for a 16-h·d−1 photoperiod. The lowest total GS content was found in cabbage microgreens under a 12-h·d−1 photoperiod and in Chinese kale microgreens under 16-h·d−1 photoperiod. In conclusion, the photoperiod of 14~16 h·d−1, and 90 μmol·m−2·s−1 and 70 μmol·m−2·s−1 PPFD for cabbage and Chinese kale microgreens, respectively, were optimal for cultivation.

Insights into the growth parameters, mineral composition, protein and UHPLC–QTOF–LC/MS‐based non‐targeted metabolomic fingerprints of wheatgrass as a function of photoperiod and temperature

“…Liu et al . (2022) also reported an increase in total flavonoid contents of brassica microgreens under prolonged photoperiod. This indicates that some metabolites were significantly affected by higher growing temperatures than photoperiod durations.…”

Optimal ratio of spectrum, light intensity and photoperiod to minimize costs when growing microgreens

“…In a study [29], aboveground biomass increased by 16.0% in lettuce and 18.7% in mizuna in response to an increase in photoperiod from 10 to 20 h. Thus, extending the photoperiod and reducing PPFD increased the growth of lettuce and mizuna by increasing light interception and quantum yield of the photosystem. Increasing light intensity increases vitamin C and decreases nitrates, while increasing photoperiod has no effect on vitamin C changes and increases nitrates in cabbage and Chinese cabbage microgreens [30]. As we can see, the effect of the light intensity/photoperiod ratio within a single daylight integral is not unambiguous.…”

Brassicaceae Microgreens: Phytochemical Compositions, Influences of Growing Practices, Postharvest Technology, Health, and Food Applications

“…One study assessed the effect of different light intensities and photoperiods on the antioxidant properties of BM. 100 The results showed a significant association between light intensity and the antioxidant capacity of the BM. Although the effect was species-specific, different LED light treatments affected the glucosinolate content of broccoli, cabbage, and radish microgreens.…”

“…Similarly, 665 nm red light treatments did not show any detrimental impact on the phenolic contents of mustard, red pak choi, and tatsoi microgreens. One study assessed the effect of different light intensities and photoperiods on the antioxidant properties of BM . The results showed a significant association between light intensity and the antioxidant capacity of the BM.…”