Radish (Raphanus sativus L.) is highly nutritious and contains antioxidants that help reduce the risk of diseases. Light is a crucial factor in their growth and the stimulation of secondary metabolite production. Therefore, this study aimed to investigate the effects of light spectra on the development, physiological responses, and antioxidant capacity of radish varieties including cherry belle (CB), black Spanish (BS), hailstone white (HW), Malaga violet (MV), and sparkler white tip (SW) under a controlled environment. Various spectra of red (R), green (G), and blue (B) light were used. The study found that using a combination of red and blue light (3R:1B) resulted in the highest growth in root diameter, fresh weight, and dry weight across all five radish varieties, with values ranging from 1.83 to 4.63 cm, 13.58 to 89.33 g, and 1.20 to 4.64 g, respectively. In terms of physiological responses, the CB and BS varieties showed a higher photosynthetic rate after exposure to mixed red and blue light (1R:3B, 3R:1B). Additionally, adding green light to the red and blue light also enhanced the photosynthetic rate, with statistically significant differences ranging from 3.31 to 3.99 µmol m⁻² s⁻¹. The SW variety of radish exhibited an increase in phenolic compounds, flavonoids, and anthocyanins when exposed to light spectra of 1R:1G:1B, 1R:2G:1B, 1R:3G:1B, and 1R:3B. The highest levels of phenolic compounds were 4.67–5.14 mg GAE/g DW, flavonoids were 1.62–1.96 mg Rutin/g DW, and anthocyanins were 1.20–1.58 µg/g DW. However, the antioxidant capacity of five radish varieties under different light spectra did not show significant differences. Thus, the growth, photosynthesis, and antioxidant capacity depend on the optimal light spectrum for each radish variety.

Light spectrum is a crucial environmental factor influencing plant growth and secondary metabolite production in controlled-environment agriculture. This study investigated the combined effects of light spectral composition on growth performance and andrographolide accumulation in Andrographis paniculata (Burm.f.) cultivated in a plant factory system. Two Thai cultivars, RBR and TTT, were grown under white light and various red–green–blue (R:G:B) LED ratios during the vegetative and flowering stages. Plant morphological traits, biomass accumulation, and andrographolide derivatives (AP1, AP4, AP6, and total AP) were quantified. Growth and biomass production were significantly enhanced under white light and red-enriched spectra, particularly during the vegetative stage, whereas stem elongation exhibited reduced sensitivity to light spectral quality during the flowering stage. In contrast, andrographolide accumulation showed a strong cultivar-dependent response to light spectrum. The TTT cultivar showed pronounced increases in AP1, AP4, AP6, and total AP under blue-enriched spectra, with the 60B:10G:30R treatment producing the highest total diterpenoid content in both cultivars, while the RBR cultivar displayed limited responsiveness to spectral variation. These results demonstrate light spectrum affecting both biomass production and phytochemical accumulation. Optimization of light spectral composition combined with appropriate cultivar selection offers an effective strategy for enhancing pharmaceutical-grade andrographolide production in plant factory systems.