Abstract
Light-emitting diodes (LEDs) are an artificial light source used in indoor cultivation to influence plant growth, photosynthesis performance and secondary metabolite synthesis. Holy basil plants (Ocimum tenuiflorum) were cultivated under fully controlled environmental conditions with different red (R) and blue (B) light intensity ratios (3R:1B, 1R:1B and 1R:3B), along with combined green (G) LED (2R:1G:2B). The photosynthetic activities of both cultivars were maximal under 3R:1B. However, the highest fresh (FW) and dry (DW) weight values of green holy basil were recorded under 3R:1B and 2R:1G:2B, significantly higher than those under alternative light conditions. For red holy basil, the highest FW and DW were recorded under 1R:3B. Moreover, 2R:1G:2B treatment promoted pigment (chlorophyll and carotenoid) accumulation in green holy basil, while red holy basil was found to be rich in both pigments under 3R:1B. Antioxidant capacity was also influenced by light spectrum, resulting in greater total phenolic content (TPC) and DPPH accumulation in both cultivars under 1R:3B. The highest content of flavonoid in green holy basil was detected under 1R:1B; meanwhile, 1R:3B treatment significantly promoted flavonoid content in red holy basil. In addition, anthocyanin content increased in red holy basil under 1R:3B conditions. Gas chromatography coupled with mass spectrometry (GC–MS/MS) analysis of chemical composition showed higher proportional accumulation in Methyleugenol and Caryophyllene of two cultivars grown under all light spectrum ratios at two developmental stages. Overall, specific light spectrum ratios induced different chemical composition responses in each cultivar and at each developmental stage. These results suggest that 3R:1B was favorable for biomass accumulation and photosynthetic responses in green holy basil, while 1R:3B provided antioxidant accumulation. For red holy basil cultivation, 1R:3B provided optimal growing conditions, promoting improvements in plant biomass, and physiological and antioxidant capacities.
Highlights
Physiology, morphology, and gene expression by initiating the signaling of phytochromes, phototropins, and cryptochromes in photoreceptors[15,16] to regulate plant growth, morphological processes, chloroplast accumulation, and secondary metabolite b iosynthesis[17,18,19]
Most studies have shown the important influence of R and B light, there is evidence that green (G) light plays an important role in regulating physiological responses and secondary metabolite biosyntheses such as sugar content in strawberries[27], total polyphenol content in lettuce[28], and vitamin C levels in tomatoes and s pinach[24,27]
On day 14 after sowing, well-developed seedlings with true leaves and roots were transplanted into a deep-flow-technique (DFT) hydroponic system in a plant factory with artificial light (PFAL) where plants are cultivated until harvest under fully controlled environmental conditions[33]
Summary
Physiology, morphology, and gene expression by initiating the signaling of phytochromes, phototropins, and cryptochromes in photoreceptors[15,16] to regulate plant growth, morphological processes, chloroplast accumulation, and secondary metabolite b iosynthesis[17,18,19]. Most studies have shown the important influence of R and B light, there is evidence that green (G) light (peaking around 510 nm) plays an important role in regulating physiological responses and secondary metabolite biosyntheses such as sugar content in strawberries[27], total polyphenol content in lettuce[28], and vitamin C levels in tomatoes and s pinach[24,27]. We evaluate the photosynthetic responses in carbon fixation and plant light reaction (the initial photosynthesis stage involving light to chemical energy conversion; ATP and NADPH) under R and B light intensity ratios and evaluate changes in antioxidant capacity and chemical profile in green and red holy basil during the harvesting stage
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