This study was conducted to investigate effects of LED light quality on the growth and photomorphogenesis of basil (cv. ‘Amethyst Improved’) in a closed-type plant factory. Basil was sown on a urethane sponge and grown for two weeks under a White-LED. When the first main leaf appeared, the plants were transplanted into a nutrient solution hydroponic system (24 ± 2 °C, RH 55±10%) and using a standard nutrient solution for leafy vegetables (N 17.3, P 4.0, K 8.0, Ca 8.0, Mg 4.0, S 4.0 me·L^-1). To compare growth and internal traits of basil under various light qualities, QD-LED (combining blue, red, and far-red light), Blue+Red-LED (blue and red wavelengths at a ratio of 1:3), White-LED, 100% Blue-LED, and 100% Red-LED were used to cultivate basil for 35 days. Photosynthetic photon flux density (PPFD) was 200 ± 10 μmol·m-2·s^-1 and the light was provided for 16/8 hours (Light/Dark). The plant height was significantly the longest at 26.1 cm in QD-LED, and the number of leaves was the highest at 16.00 ea in QD-LED, but not significant. The leaf length was the longest at 10.9 cm in QD-LED and the shortest at 8.10 cm in White-LED. The leaf width was up to 26% wider in Blue+Red-LED, but there was no statistical significance. The leaf thickness was the thickest at 0.33 mm for Blue+Red-LED and Red-LED, which have a high proportion of red light, and the thinnest at 0.26 mm for Blue-LED. In the case of the curvature index (CI), which indicates the morphological characteristics of basil leaves, the values were highest for Blue+Red-LED and Red-LED. The internode length and leaf stalk length were significantly the longest at 5.73 cm and 3.04 cm, respectively, for QD-LED, and the stem diameter at 5.26 mm for QD-LED. The shoot fresh weight was 26.0 g in QD-LED, which was significantly higher than the other treatment groups by up to four times, but the root fresh weight was the highest at 5.99 g in Blue+Red-LED. On the other hand, the shoot and root dry matter ratio were the highest at about 9% and 5%, respectively, in White-LED. The maximum quantum yield (FvFm) did not differ significantly between the treatment groups, but the value was significantly lowest at 0.79 for Red-LED. The chlorophyll content (SPAD), normalized difference vegetation index (NDVI), and anthocyanin reflectance index (ARI1) values were up to 27% higher in Blue+Red-LED than in other treatment. Also, the DPPH radical scavenging activity and total phenol content were the highest in Red-LED at 74% and 9.47 mgGAE·g^-1FW, respectively. As a result, basil (cv. ‘Amethyst Improved’) grew best in QD-LED, and its antioxidant effect was the best in Red-LED. In addition, it was confirmed that the curvature and morphological characteristics of basil leaves changed depending on the ratio of red light at 600-700 nm.

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.