Light Spectrum, Intensity, and Photoperiod as Drivers of Redox Regulation in Primary and Secondary Plant Metabolism: Central Roles of LED Lighting Systems

Light is not only the primary energy source for photosynthesis but also a fundamental environmental signal regulating plant growth, development, and metabolism. Recent advances in light-emitting diode (LED) technology have enabled precise manipulation of light spectrum, intensity, and photoperiod, providing unprecedented opportunities to regulate plant metabolism through redox-dependent mechanisms. Although numerous studies have investigated the physiological effects of LED lighting, the mechanistic links among photoreceptor activation, redox homeostasis, and metabolic reprogramming remain fragmented. This review addresses this knowledge gap by providing a comprehensive and critical synthesis of recent advances in LED-mediated regulation of plant metabolism. Particular emphasis is placed on the central role of redox homeostasis as an integrative regulatory hub that links photoreceptor signaling, reactive oxygen species (ROS), antioxidant systems, phytohormonal crosstalk, and redox-sensitive transcription factors to coordinate primary and secondary metabolism. The review discusses how different wavelengths, light intensities, and photoperiod regimes regulate carbon, nitrogen, and sulfur metabolism, as well as amino acid, lipid, and nucleic acid metabolism, and the biosynthesis of phenolics, flavonoids, carotenoids, alkaloids, glucosinolates, and terpenoids. Recent evidence regarding photoreceptor-mediated signaling, HY5–COP1 regulation, ROS-dependent transcriptional networks, and metabolic engineering strategies is critically evaluated to explain the mechanistic basis of LED-induced metabolic reprogramming. Emerging technologies, including dynamic LED systems, artificial intelligence-assisted spectral optimization, multi-omics approaches, genome editing, and plant–microbiome interactions, are highlighted as promising tools for precision crop management. Overall, this review proposes a conceptual framework in which programmable LED lighting functions as a systems-level regulator of plant metabolism, providing new perspectives for optimizing phytochemical production, crop quality, and the sustainable development of controlled-environment agriculture.