Paper Reviewed
Qiang, Q., Gao, Y., Yu, B., Wang, M., Ni, W., Li, S., Zhang, T., Li, W. and Lin, L. 2020. Elevated CO2 enhances growth and differentially affects saponin content in Paris polyphylla var. yunnanensis. Industrial Crops & Products 147: 112124.

Multi-leaf paris (Paris polyphylla) is a shade-tolerant herb common to southwestern China within evergreen broad-leaved forests. It is commonly utilized in traditional Chinese medicine thanks to a class of steroidal saponins found within its rhizome, which secondary metabolites have been shown to successfully stop bleeding (Sun et al., 2014), reduce inflammation (Zhu et al., 2019) and inhibit the proliferation of cancer cells (Lee et al., 2009; Zhang et al., 2018). Thus, there is great interest in industrializing this species for use in producing medicines and healthcare products. However, efforts to do so are hampered by the fact that P. polyphylla is a slow-growing plant, requiring up to 10 years from seed germination to harvest.

In an effect to explore the possibility of speeding up the growth of mulit-leaf paris and the production of its medicinal compounds, Qiang et al. (2020) set out to examine the response of two cultivars of this species to elevated concentrations of atmospheric CO2.

The work was conducted in a controlled-environment greenhouse in Kunming, China. The two cultivars included one from a warm and humid habitat (CY) and one from a locale that is cold and dry (WY). Plants from both cultivars at the one-leaf seedling stage were subjected to ambient (400 ppm) or elevated (800 ppm) CO2 levels for a period of 30 days. All other conditions were maintained under normal growth environments for the species.

Exposure to elevated CO2 led to significant improvement in various photosynthetic and growth-related parameters. Net photosynthesis at the end of the 30 day experiment, for example, increased by approximately 110% and 178% in the WY and CY cultivars, respectively, which helped lead to improvements in water use efficiency of 87% for WY and 143% for CY. Additionally, elevated CO2 stimulated plant fresh weight, increasing it by 11.4% in the CY cultivar and by 18.3% in WY.

With respect to the production of steroidal saponins under elevated CO2 conditions, Qiang et al. report that although their concentrations declined slightly, an "increased amount of saponins was produced." Thus, elevated CO2 positively impacted the overall production or content of these important medicinal compounds.

Consequently, in light of the above findings, it would appear that rising atmospheric CO2 will benefit the growth of multi-leaf paris and its key secondary metabolites, which has important medical and health-related implications.

References
Lee, R.K.Y., Ong, R.C.Y., Cheung, J.Y.N., Li, Y.C., Chan, J.Y.W., Lee, M.M.S., Suen, Y.K., Fung, K.P., Ho, H.P., Bao, Y., Li, M., Kwok, T.T. and Kong, S.K. 2009. Polyphyllin D - a potential anti-cancer agent to kill hepatocarcinoma cells with multi-drug resistance. Current Chemical Biology 3: 89-99.

Sun, C.L., Ni, W., Yan, H., Liu, Z.H., Yang, L., Si, Y.A., Hua, Y., Chen, C.X., He, L., Zhao, J.H. and Liu, H.Y. 2014. Steroidal saponins with induced platelet aggregation activity from the aerial parts of Paris verticillata. Steroids 92: 90-95.

Zhang, J.L., Ma, Y.Z., Hu, W.L., Lan, G.Y. 2018. Effects of high temperature stress on physiological indicators of Paris polyphylla var. yunnanensis. Chinese Traditional and Herbal Drugs 36: 100-106.

Zhu, T.T., Wu, W.J., Yang, S.Y., Li, D.L., Sun, D.J. and He, L. 2019. Polyphyllin I inhibits propionibacterium acnes-induced inflammation in vitro. Inflammation 42: 35-44.