Red and blue light-mediated physiological and metabolic insights in Artemisia annua L

The impact of quality of light on plant growth and development has been extensively studied. However, the interplay between photosynthesis and metabolic regulation in Artemisia annua remains largely unexplored. To address this gap, we investigated how various light qualities; monochromatic red (R), blue (B), a 1:1 red-blue combination (RB), and broad-spectrum white light (W); affect physiological parameters, photosynthetic activity, and metabolic processes. Plants were exposed to these light conditions at a photosynthetic photon flux density (PPFD) of 200 mu mol & sdot; m- 2 & sdot; s- 1 for 10 days. Exposure to different light treatments resulted in significant changes in morphological attributes, chlorophyll and carotenoid content, stomatal conductance, intercellular COQ concentration, and transpiration rates. DPPH-scavenging activity and ascorbic acid levels increased under RB and B light, with increments of 20.76 %-25.6 % and 23 %-43.29 %, respectively, compared to W light. Gas chromatography-mass spectrometry (GC-MS) analysis showed the highest monoterpene concentration (36 %) under B light, followed by RB light (31 %), R light (28 %), and W light (27 %). Further, High-resolution mass spectrometry (HRMS) indicated elevated levels of flavonoids, terpenes, phenolics, and other organic compounds in RB light-exposed plants, with B light showing the following highest levels. Additionally, vital photosynthesis- regulating genes such as LHCII, CAO, TK, PsbA, PsaB, PsbD, RbcL, ndhB, RbcS, PetB, PetD, AtpA, and FBP demonstrated significant upregulation under various light conditions. Genes involved in artemisinin biosynthesis, including HMGS, MK, MCT, MPDC, CYP71AV1, and 1,8-cineol synthase, showed increases of 38.4 %- 13.3 %, 20.4 %-22.4 %, 29.5 %-37.5 %, 15 %-16 %, 43 %-68 %, and 93.4 %-106.5 %, respectively, in response to B and RB light. These findings underscore the complex influence of various light qualities on the metabolic pathways of A. annua, providing a basis for future research.