Effects of environmental and physiological factors on the production of bioactive chemicals in Panax quinquefolius L. (American ginseng)

Background/Question/Methods

American ginseng, Panax quinquefolius L., is an herbaceous perennial species endemic to North American deciduous forests. It is a favored medicinal herb and an important economic crop harvested for its bioactive compounds called ginsenosides. Currently, ginseng suffers from overharvesting of reproductive individuals which results in loss of genetic variability reducing long term population viability. There is need to develop cultivars of ginseng to enhance commercial production in order to protect wild populations from harvest. For these endeavors to be successful, a better understanding of the environmental, physiological, and genetic factors affecting ginsenoside production is needed. We investigated the influences of environmental (soil water content, nutrient availability, light availability, sunfleck duration) and physiological (photosynthetic capacity and light responses) factors on the production of ginsenosides (Rg₁, Re, Rb₁, Rb₂, Rc, and Rd) in three wild populations in western North Carolina (LB, PC, SC).  High-performance liquid chromatography (HPLC) was used to determine ginsenoside concentrations (µg/mg) of roots of 13 individuals at each population. Environmental, physiological factors and ginsenoside production were compared among sites using ANOVA. Ginsenoside production was related to environmental and physiological factors using regression analysis.

Results/Conclusions

Light environments and nutrient availability were similar among sites. There were also no differences in plant age or biomass among sites. All populations contained ginsenosides Rg₁, Rb₁, Rb₂, Rc, and Rd, but one population also included Re, suggesting a different chemotype at that population. Combined root ginsenoside content (concentration*biomass) did not vary among sites. Root biomass increased with age (p = 0.0202) and combined ginsenoside content increased with biomass (p = 0.0021) resulting in greater total content in larger roots. Combined ginsenoside content increased with maximum photosynthetic rate (p = 0.0411) but did not vary with light or nutrient availabilities. Increased photosynthetic capacity appears to increase the production of ginsenosides, possibly through “over-flow” carbon metabolism. There was little variation in environmental factors among wild populations so we were unable to accurately assess their impact on ginsenoside production.  Current research includes growing ginseng in controlled-environment growth chambers with a greater range of environmental factors to better assess their effects on ginsenoside production.  Additionally, members of our lab our assessing the genetic variability within and among these populations. We hope to contribute to the development of cultivars and cultivation protocols for the commercial production of ginseng in western North Carolina.