Effects of different light qualities and plant growth regulators on the growth and secondary metabolites contents of L. macranthoides seedlings

Lonicera macranthoides , a medicinal herb mainly distributed in South China, is widely utilized in Chinese traditional medicines for its high yield and strong pharmacological properties rich in phenolic acids and flavonoids. However, the factors regulating plant growth and secondary metabolism in L. macranthoides are still largely unknown. In this study, the effects of different light qualities and hormone combinations on seedlings growth performance and metabolites production were investigated. The results showed that plants under red light produced greatest biomass of the shoots and roots, and also promoted plant photosynthesis as indicated by significantly greater values for Pn, Gs, Ci, and Tr, followed by white and blue LED. The tissue culture seedlings exhibited maximum plant height and stem diameter on the medium with 1.0mg/L 6-benzyladenine (BA) + 1.0mg/L Indole 3-butyric acid (IBA), while produced the highest amounts of phenolic acids and flavonoids in medium containing 2.0mg/L BA + 0.2mg/L IBA. Red light dramatically enhanced the accumulation of chlorogenic acid (CGA), ferulic acid, luteoloside, and rutin than those under other light spectra conditions on the medium with low level of auxin. However, higher levels of auxin dramatically inhibited the CGA production under red light. Moreover, blue light can promote the accumulation of chlorogenic acid and luteoloside on these two media. The results indicate that the plant growth and secondary metabolism were dramatically influenced by light quality and auxin/cytokinin combinations. Light and auxin signaling crosstalk programmed secondary metabolites accumulation. Our findings provide effective strategies aiming to enhance biomass yield and bioactive compounds production in L. macranthoides .