Growth and Quality Responses of Ligularia stenocephala to Different LED Light Spectra in a Plant Factory

Light quality is a crucial factor influencing plant growth and physiological quality in controlled-environment agriculture (CEA). This study examined how different LED light spectra affect the growth and internal quality of Ligularia stenocephala cultivated in a plant factory. The plants were grown under five types of LED light: monochromatic red, monochromatic blue, a combination of blue and red, white LEDs, and quantum dot (QD) LEDs. We evaluated various growth parameters, biomass accumulation, chlorophyll indices, and antioxidant capacity. Monochromatic red LEDs promoted rapid early growth and stem elongation but led to lower chlorophyll accumulation and antioxidant capacity. In contrast, monochromatic blue LEDs increased chlorophyll content, leaf thickness, dry matter accumulation, and antioxidant capacity, although they limited leaf expansion and shoot biomass. Composite-spectrum LEDs displayed distinct trade-offs between growth and quality parameters. QD LEDs maximized shoot biomass accumulation while maintaining moderate internal quality, whereas Blue+Red LEDs provided a balanced combination of significant biomass and enhanced phytochemical content. Principal component analysis indicated a fundamental trade-off between quality-related (PC1: 57.6%) and growth-related (PC2: 22.7%) parameters, showing that no single LED spectrum could optimize all cultivation factors simultaneously. Therefore, LED selection should align strategically with specific cultivation goals: use QD LEDs for volume-based production, Blue+Red LEDs for balanced premium markets, and blue LEDs for specialty functional vegetables. These findings underscore the importance of context-dependent lighting optimization strategies in plant factory systems and offer a framework for selecting the most effective LED spectra to enhance crop performance in CEA.