## 2 Materials and Methods
### Plant Materials and Microgreens Production  
Seeds of two cultivars of cabbage (_Brassica oleracea_ var. _capitata_), namely white (f. _alba_, \"Kamienna glowa\") and red (f. _rubra_, \"Haco\"), were obtained from the seed company \"W. Legutko\" in Poland. These seeds were sown in a commercial peat substrate (Hartmann, Poland), specifically designed for vegetable seedling cultivation. The substrate had the following nutrient composition: N-NH\({}_{4}\) 21, N-NO\({}_{3}\) 252, P 87, K 239, Ca 1457, Mg 166, S-SO\({}_{4}\) 221, Fe 27.4, Zn 1.4, Mn 4.9, Cu 0.4, Cl 30, Na 50, with a pH 5.83 and an electrical conductivity of 1.223 mS cm\({}^{-1}\). Seeds were sown directly on trays (3 g per tray) for seedling cultivation, measuring 30 \(\times\) 50 \(\times\) 5 cm (7.5 L). Plants were not additionally fertilized during cultivation; watering was conducted every few days, depending on the needs of the plants.  
Cabbages were grown on tables in growth chambers, each equipped with its own independent lighting, and light of different spectral compositions was used in each chamber. The temperature in the growth chamber was set to 23 \({}^{\circ}\)C for the first two days and was then maintained at 21 \({}^{\circ}\)C during the day and 17 \({}^{\circ}\)C at night (\(\pm\)2 \({}^{\circ}\)C). The relative humidity was 60-70%. The light sources were modules equipped with semiconductor diodes that provided white light, further enhanced with blue or red light. The red, blue, and white light came from a high-power solid-state lighting module (LED) (SMD type, Seoul Semiconductor, Ansan-si, South Korea). The spectrum of white light was shown in Table 1 and Figure 1.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Light Color**} & **Wavelength** & **PFPD (W)** & **\% for** & **PFPD (W)** & **\% for** & **\% for** \\  & **(nm)** & **(\(\mu\)mol m\({}^{-2}\) s\({}^{-1}\))** & **W light** & **(\(\mu\)mol m\({}^{-2}\) s\({}^{-1}\))** & **W + R** & **W + B** \\ \hline UV & 320–380 & 0.69 & 0.3 & 0.5 & 0.2 & 0.2 \\ Violet & 380–450 & 21.10 & 8.9 & 15.4 & 6.6 & 6.6 \\ Blue & 450–495 & 41.51 & 17.6 & 30.3 & 13.0 & 38.9 \\ Green & 495–570 & 73.30 & 31.1 & 53.5 & 23.0 & 23.0 \\ Gold & 570–590 & 25.62 & 10.9 & 18.7 & 8.1 & 8.1 \\ Orange & 590–620 & 29.87 & 12.7 & 21.8 & 9.4 & 9.4 \\ Red (R) & 620–700 & 36.17 & 15.3 & 26.4 & 37.2 & 11.4 \\ Far Red (FR) & 700–780 & 7.67 & 3.3 & 5.6 & 2.4 & 2.4 \\ Sum & 320–780 & 235.9 & 100 & 172.2 & 100 & 100 \\ \hline R:FR & & 4.7 & - & 4.7 & 15.5 & - \\ \hline \end{tabular}
\end{table}
Table 1: Characteristic of the white light source.  
Figure 1: The spectral composition of the lamps for white light (W), white light with red light (W + R), and white light with blue light (W + B).  
The microgreens were grown under 16 h light/8 h dark conditions with a daylight dose of about 13.2 mol m\({}^{-2}\) s\({}^{-1}\). The proportion of red light to blue light for each combination was as follows: white light: 0.87; white light with red light: 2.86; white light with blue light: 0.29. LED light intensity and spectral distribution were monitored by a PAR-10 quantum sensor (Sonopan, Bialystok, Poland) and a BLACK-Comet CXR UV-VIS spectroradiometer (280-900 nm, StellarNet Inc., Tampa, FL, USA), respectively.  
All cabbage microgreens were harvested 14 days after sowing, when they started to form the first true leaves. For chemical analyses, the plants were freeze-dried immediately after harvesting (Alpha 1-2/LD Plus freeze dryer, Christ, Osterode am Harz, Germany).