Deciphering the potential of LED lights in modulating morpho-physiological growth, specialized metabolites, and gene expression pattern in Valeriana jatamansi Jones

Valeriana jatamansi Jones is a well-known Himalayan medicinal rhizomatous herb due to the presence of therapeutically important bioactive metabolites. The precise manipulation of LED light quality and conditions acts as a powerful tool to sculpt plant growth, fine-tune photosynthetic performance, and boost phytochemical biosynthesis in controlled in vitro environments. Thus, in the present investigation, the effect of different LED lights (yellow, red, blue, and white as a control) on the growth, physiological responses, biochemical parameters, secondary metabolite accumulation, and gene expression pattern of in vitro raised V. jatamansi was systematically evaluated. Maximum shoot length (9.71 cm) was observed under blue light, whereas maximum leaf number (20.22) and root number (15.11) were found under white light. Red light promoted the maximum fresh weight in both leaf (1.42 g) and root (1.47 g) tissues. In root tissue, the highest total phenolic content (126.30 µg QE/mg DW) and flavonoid content (211.79 µg GAE/mg DW) were recorded under yellow and white light, respectively. Chlorophyll fluorescence measurements indicated stable photosynthetic efficiency across all light treatments. Peroxidase and catalase activity in root and leaf tissue were highest in white light conditions. The accumulation of valtrate was maximum under white and yellow light in leaf (0.090 mg/g DW) and root tissue (0.167 mg/g DW), respectively. Furthermore, qRT-PCR analysis showed significant upregulation of iridoid biosynthetic pathway genes (GES, G10H , and 7DLS) under yellow and white light. This study highlights the potential of LED lights for optimizing growth and enhancing the production of bioactive metabolites in V. jatamansi , offering a sustainable approach for its conservation and future large-scale pharmaceutical applications under controlled in vitro conditions.