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 (Fv/Fm). 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.

光周期调节植物中不同的形态生理过程，直接影响光合作用，进而影响初级和次级代谢。迄今为止，尚无研究报道光周期对植物蜕皮激素类生物合成的影响，例如20-羟基蜕皮激素（20-E）。在这里，我们评估了光周期对体外生长的Pfaffia glomerata（20-E的重要药用物种和生产者）的发育和代谢的影响。两个P. glomerata在不同的光周期：4、8、16和24 h下，将种质（Ac22和Ac43）培养40天。然后，评估与该化合物的合成有关的生长，生理性能，20-E含量和基因表达。较长的光周期导致两个种的光合速率，生长和生物量积累较高。P. glomerata对测试的不同光周期表现出很大的可塑性，并且没有光抑制的迹象（F v / Fm）。初级代谢受光周期的调节，可溶性糖，淀粉和氨基酸的产生存在显着差异。花青素的生产也受到光周期的影响。然而，这些种质表现出相反的响应，其中较长的光周期导致Ac22中的花青素含量最高，而Ac43中的最低，从而反映了不同的光照条件适应策略。由于更好的光合作用性能和更高的碳利用率，在更长的光周期中，球果假单胞菌积累了更多的20-E。这样，为更长的光周期生长的P. glomerata植物可能代表了获得具有更大生物量和更高20-E产量的植物的策略。