The combination of blue and red LED light improves growth and phenolic acid contents in Salvia miltiorrhiza Bunge

Abstract

Salvia miltiorrhiza Bunge is a medicinal plant species commonly used in China and other East Asian countries. There is a large market demand for this herb, and improving its yield and quality is an urgent problem to be solved in production practice. Artificial light sources have been widely used in the production of vegetables and medicinal plants, but little is known about the effects of light quality on the growth and secondary metabolites accumulation in S. miltiorrhiza. In this study, the effects of monochromic blue light (460 nm, B), monochromic red light (635 nm, R), white light, and various combinations of B and R light (9B:1R, 7B:3R, 1B:1R, 3B:7R and 1B:9R) on the growth and phenolic acid accumulation of S. miltiorrhiza were investigated. The results showed that, the growth and contents of rosmarinic acid and salvianolic acid B in S. miltiorrhiza were simultaneously stimulated under 3B:7R. The transcripts of key enzyme-encoding genes involved in the rosmarinic acid pathway were measured, and the expression of SmPAL1 and Sm4CL1 was significantly increased under combined blue and red light. The results of site-directed mutagenesis revealed that the GT1-motif in the SmPAL1 promoter region, I-Box, ATC-motif and TCT-motif in the Sm4CL1 promoter region were related to the responses of these two genes to combined blue and red light. Taken together, the results of this work indicated that, the combined blue and red light promoted the growth of S. miltiorrhiza and enhanced the accumulation of phenolic acids by up-regulating the transcription of SmPAL1 and Sm4CL1 in this herb. Light quality is an important environmental factor that effects yield and quality of S. miltiorrhiza.