Photoperiod modulates growth and pigments and 20-hydroxyecdysone accumulation in Brazilian ginseng [Pfaffia glomerata (Spreng.) Pedersen] grown in vitro

Photoperiod regulates different morphophysiological processes in plants, directly impacting photosynthetic performance and, consequently, primary and secondary metabolism. To date, there are no studies reporting the influence of photoperiod on the biosynthesis of phytoecdysteroids, such as 20-hydroxyecdisone (20-E). Here, we evaluated the effects of photoperiod on the development and metabolism of in vitro grown Pfaffia glomerata , an important medicinal species and producer of 20-E. Two P. glomerata accessions (Ac22 and Ac43) were cultivated for 40 days under different photoperiods: 4, 8, 16, and 24 h. Then, growth, physiological performance, 20-E content and gene expression related to the synthesis of this compound were evaluated. Longer photoperiods resulted in higher photosynthetic rates, growth, and biomass accumulation in both accessions. P. glomerata showed great plasticity to the different photoperiods tested and no sign of photoinhibition ( F v/ F m). Primary metabolism was modulated by photoperiod, with marked differences in the production of soluble sugars, starch, and amino acids. Anthocyanin production was also affected by the photoperiod. However, the accessions showed contrasting responses, in which longer photoperiods led to the highest anthocyanin contents in Ac22 and the lowest in Ac43, reflecting different adaptive strategies the light conditions. As a result of better photosynthetic performance and higher carbon availability, P. glomerata accumulated more 20-E during longer photoperiods. In this way, growing P. glomerata plants for longer photoperiods may represent a strategy for obtaining plants with larger biomass and higher 20-E yields. Key Message Photoperiod regulates the primary and secondary metabolism of P. glomerata plants grown in vitro, and longer photoperiods increase growth, photosynthetic performance, and accumulation of the phytoecdysteroid 20-hydroxyecdysone (20-E).