Influence of Different Light Spectra on Metabolism, Nutrition, and Photosynthetic Efficiency in the Development of Bell Pepper Seedlings

The spectral quality of light plays a fundamental role in regulating plant growth, photosynthesis, and metabolism, with LED technology being a promising tool for optimizing seedling production in controlled environments. However, studies that comprehensively evaluate the effects of different light spectra on the biometric, physiological, biochemical, and nutritional responses of pepper (Capsicum annuum L.) seedlings are still limited. Thus, this study aimed to evaluate the effect of different LED light spectra. This study investigated the effects of the colors white light (W), full-spectrum white light (WF), blue (B - 450 nm), red (R - 660 nm), 50% red (660 nm) and 50% blue (450 nm) (RB), and green (G - 530 nm) on the growth, photosynthetic performance, production of bioactive compounds, and nutrient absorption in bell pepper seedlings. The experimental design was completely randomized, with three replicates of 10 plants per treatment. The results were subjected to analysis of variance (ANOVA), and the parameters with statistical significance were analyzed using Tukey's multiple comparison test with a 95% confidence interval. Biometric parameters, photosynthetic parameters, chlorophyll fluorescence, phenolic compounds, flavonoids, anthocyanins, and macro- and micronutrient contents were evaluated, with the results integrated using principal component analysis (PCA). The different light spectra promoted specific and complementary physiological responses. The results indicated that R light promoted greater plant height and accumulation of aboveground biomass, while W light and the RB combination favored leaf expansion, and RB light resulted in greater absorption of essential micronutrients such as Zn, Cu, and Mn. The G spectrum induced greater accumulation of total phenolic compounds, suggesting the activation of secondary metabolic pathways related to oxidative stress. Photosynthetic performance was optimized under W light, reflecting greater CO₂ assimilation. B light showed less expressive results for biometric parameters, photosynthetic assimilation rate, and water use efficiency. Principal component analysis explained 80.46% of the total variability of the data, highlighting associations between the different light spectra and the biometric, physiological, biochemical, and nutritional responses of the seedlings. The results demonstrated that the spectral quality of light can modulate, in an integrated way, the growth, photosynthetic performance, mineral nutrition, and secondary metabolism of pepper seedlings, according to the production objective. These findings reinforce the potential of LED technology as a tool to optimize the quality of seedlings produced in controlled environments.