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Effects of light deficiency on the accumulation of saikosaponins and the ecophysiological characteristics of wild Bupleurum chinense DC. in China

Gong, Jirui, Liu, Min, Xu, Sha, Jiang, Yuan, Pan, Yan, Zhai, Zhanwei, Luo, Qinpu, Yang, Lili, Wang, Yihui
Industrial crops and products 2017 v.99 pp. 179-188
Bupleurum, Oriental traditional medicine, aboveground biomass, agroforestry, antioxidants, carbon, carotenoids, catalase, chlorophyll, ecophysiology, electron transfer, energy, leaf area, leaves, light harvesting complex, light intensity, malondialdehyde, medicinal properties, peroxidase, phosphates, photoinhibition, photosystem II, respiratory rate, secondary metabolites, shade tolerance, stress response, superoxide dismutase, understory, wild plants, China
Bupleurum chinense DC. is one of the most important traditional Chinese medicines. Among its primary pharmacologically active components, saikosaponins play a vital role. We investigated the ecophysiological characteristics, accumulation of secondary metabolites, and antioxidant system of wild plants at low light intensity in the forest understory at shady and sunny sites. Compared with plants at sunny sites, plants at the shady site were more abundant, had higher specific leaf area (SLA), a lower maximum electron transport rate (Jmax), higher triose phosphate utilization (TPU), and higher chlorophyll b content (Chlb), but lower net photosynthesis (Pn), root and aboveground biomass, dark respiration rate (Rd), light compensation point (LCP), chlorophyll a to b ratio, carotenoid content, and nonphotochemical quenching (NPQ). These features suggest that under low light conditions, the species developed larger leaves to catch more light energy through light-harvesting complex II to increase its photosynthetic efficiency (its ability to use weak light) and photosynthetic electron transport, thereby improving carbon metabolism and survival. The maximum quantum efficiency of photosystem II was about 0.8 at both sites; thus, photoinhibition was not a major problem. Contents of saikosaponins a and d and the total saikosaponin content (SSa, SSd, and SStotal) were much higher at the shady site, accompanied by increased superoxide dismutase (SOD), catalase(CAT), and peroxidases (POD) activity and decreased malondialdehyde (MDA). This suggested that low light activates antioxidant stress-response pathways, leading to increased SSa, SSd, and SStotal. Our results suggest that B. chinense has strong shade tolerance and would be suitable for cultivation in an agroforestry system.