Effects of supplemental lighting with different light qualities on growth and secondary metabolite content of Anoectochilus roxburghii

Background: Anoectochilus roxburghii is a widespread herbaceous plant with high medicinal value. Wild A. roxburghii resources face extinction due to their slow growth rate and over exploitation. The growing market demand has led to advances in the field of artificial planting of A. roxburghii. Methods to increase the economic benefits of cultivation and the production of medicinal ingredients are very useful. Methods: A. roxburghii was exposed to red light, blue light (BL), yellow light (YL), green light, or white light as supplemental lighting at night (18:00-02:00) in a greenhouse or were left in darkness (control, CK) to investigate the effects of various light qualities on growth indices, photosynthetic pigments, chlorophyll fluorescence, root vitality, stomatal density, soluble proteins, sugars, and the accumulation of secondary metabolites. Results: Supplementation of BL had a positive effect on A. roxburghii growth and secondary metabolite accumulation. Leaf number, stem diameter, fresh weight, dry weight, chlorophyll a content, and secondary metabolite (total flavonoids, total polyphenols) content increased significantly. YL treatment showed significantly higher soluble sugar and polysaccharide contents than the control. Discussion: BL treatment was conducive to promoting the growth and accumulation of secondary metabolites (total flavonoids, total polyphenols); YL treatment significantly increased the content of soluble sugar and polysaccharides more than the control. Polysaccharides and total flavonoids are important medicinal ingredients of Anoectochilus, so future research will focus on the combination of blue and YL.