| Summary: | We investigated the effects of red and blue light on the growth and content of bioactive compounds of <i>Salvia plebeia</i> R. Br in a closed-type plant production system (CPPS). The seedlings of <i>Salvia plebeia</i> R. Br. were transplanted into a deep floating technique system with nutrient recycling (pH 6.5 and electrical conductivity (EC) 1.5 dS∙m<sup>−1</sup>). The plants were cultured for a duration of 35 days at 25 ± 1 °C, with relative humidity 60 ± 5%, a 12/12 h (light/dark) photoperiod, and a light intensity of 180 µmol∙m<sup>−2</sup>∙s<sup>−1</sup> photosynthetic flux photon density, providing standard fluorescent (FL) lighting and various light qualities of red:blue ratios (10:0, 7:3, 5:5, 3:7, and 0:10) in the CPPS. The growth characteristics of <i>Salvia plebeia</i> R. Br., such as leaf length, leaf area, and fresh and dry weights of shoots, were the greatest in Red only and R7B3. The leaf shape index was the highest in Blue only and specific leaf weight was lower in FL and Blue than in the other treatments. The photosynthetic rate was the highest in R7B3. The total phenolic and flavonoid concentrations per gram of fresh weight of <i>Salvia plebeia</i> R. Br. were higher in combined light, such as R7B3, R5B5, and B3B7, than in the monochromatic light treatments. However, the antioxidant activity per fresh weight was the highest in FL. In conclusion, the results suggest that 7:3 is the most effective red and blue light ratio for production of high quality <i>Salvia plebeia</i> R. Br. in a CPPS.
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