Effects of Stage-Specific of Red to White Light on the Growth and Nutritional Properties of Pak Choi

In plant factories with artificial lighting (PFALs), spectral regulation serves as the predominant factor governing plant growth and development. The implementation of red-enriched spectral regimens during cultivation promotes biomass accumulation, whereas blue-dominant spectra enhance the biosynthesis of phytochemicals and nutritional compounds in plants. Nevertheless, systematic investigations of staged spectral regimens on both plant development and secondary metabolite biosynthesis remain limited. This study implemented a staged lighting regimen utilizing three distinct red-to-white photon flux ratios (R: W=3:1, 1:1, and 1:3) administered sequentially during critical developmental phases: seedling stage, the early growth stage (15 d after transplanting, DPA), and the late growth stage (16-30 d, DPA) in Pak choi. This study implemented four distinct staged spectral regimens to evaluate photonic treatment effects through multivariate analysis of biomass production, morphological development, photosynthetic pigments, nutritional metabolites, along with antioxidants and radical quenching capacity. The results demonstrated that the T4 treatment significantly enhanced biomass production across all developmental stages. While, the T3 treatment exhibited optimal efficacy in improving nutritional quality (particularly content of soluble proteins and Vitamin C) along with superior antioxidant capacity. The higher red-light significantly enhanced leaf expansion and carotenoid biosynthesis at the seedling stage. While higher blue-light in subsequent growth stages effectively stimulated biosynthesis of chlorophyll and antioxidants. This study established that temporal modulation of red-to-white spectral ratios during vegetative development enabled synergistic optimization of yield and quality attributes in Pak choi.