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.

Three different LED spectra (W: White light; WFR: W + far-red light; WB: W + blue light) with similar photosynthetic photon flux density (PPFD) were designed to explore the effects of supplementary far-red and blue lights on leaf color, biomass and phytochemicals of two cultivars of red-leaf lettuce (“Yanzhi” and “Red Butter”) in an artificial lighting plant factory. Lettuce plants under WB had redder leaf color and significantly higher contents of pigments, such as chlorophyll a, chlorophyll b, chlorophyll (a + b) and anthocyanins. The accumulation of health-promoting compounds, such as vitamin C, vitamin A, total phenolic compounds, total flavonoids and anthocyanins in the two lettuce cultivars were obviously enhanced by WB. Lettuce under WFR showed remarkable increase in fresh weight and dry weight; meanwhile, significant decreases of pigments, total phenolic compounds, total flavonoids and vitamin C were found. Thus, in the plant factory system, the application of WB can improve the coloration and quality of red leaf lettuce while WFR was encouraged for the purpose of elevating the yield of lettuce.

Brassicaceae baby-leaves are good source of functional phytochemicals. To investigate how Chinese kale and pak-choi baby-leaves in response to different wavebands of blue (430 nm and 465 nm) and UV-A (380 nm and 400 nm) LED, the plant growth, glucosinolates, antioxidants, and minerals were determined. Both agronomy traits and phytochemical contents were significantly affected. Blue and UV-A light played a predominant role in increasing the plant biomass and morphology, as well as the contents of antioxidant compounds (vitamin C, vitamin E, phenolics, and individual flavonols), the antioxidant activity (DPPH and FRAP), and the total glucosinolates accumulation. In particular, four light wavebands significantly decreased the content of progoitrin, while 400 nm UV-A light and 430 nm blue light were efficient in elevating the contents of sinigrin and glucobrassicin in Chinese kale. Meanwhile, 400 nm UV-A light was able to increase the contents of glucoraphanin, sinigrin, and glucobrassicin in pak-choi. From the global view of heatmap, blue lights were more efficient in increasing the yield and phytochemical levels of two baby-leaves.

Addition of selenium or application of ultraviolet A (UVA) radiation for crop production could be an effective way of producing phytochemical-rich food. This study was conducted to investigate the effects of selenium and UVA radiation, as well as their combination on growth and phytochemical contents in broccoli microgreens. There were three treatments: Se (100 μmol/L Na₂SeO₃), UVA (40 μmol/m²/s) and Se + UVA (with application of Se and UVA). The control (CK) was Se spraying-free and UVA radiation-free. Although treatment with Se or/and UVA inhibited plant growth of broccoli microgreens, results showed that phytochemical contents increased. Broccoli microgreens under the Se treatment had higher contents of total soluble sugars, total phenolic compounds, total flavonoids, ascorbic acid, Fe, and organic Se and had lower Zn content. The UVA treatment increased the contents of total chlorophylls, total soluble proteins, total phenolic compounds, and FRAP. However, the Se + UVA treatment displayed the most remarkable effect on the contents of total anthocyanins, glucoraphanin, total aliphatic glucosinolates, and total glucosinolates; here, significant interactions between Se and UVA were observed. This study provides valuable insights into the combinational selenium and UVA for improving the phytochemicals of microgreens grown in an artificial lighting plant factory.