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Effects of Very High CO2 Concentrations on Ginseng Roots
Volume 8, Number 39: 28 September 2005

Roots of the ginseng plant (Panax ginseng), which is widely cultivated in China, South Korea and Japan, have been used for medicinal purposes since Greek and Roman times.  They are well known for their anti-inflammatory, diuretic and sedative properties and are acknowledged to be effective healing agents (Gillis, 1997; Ali et al., 2005).  Normally, however, four to six years are required for ginseng roots to accumulate the amounts of the various phenolic compounds that are needed to produce their health-promoting effects.  Consequently, in an important step in the quest to develop an efficient culture system for the commercial production of ginseng root, Ali et al. investigated the effects of growing ginseng roots in suspension culture in bioreactors that were maintained in equilibrium with air that was enriched to CO2 concentrations of 10,000 ppm, 25,000 ppm and 50,000 ppm for periods of up to 45 days.

Of most immediate concern in such an experiment would be the effects of the ultra-high CO2 concentrations on root growth.  Would they be toxic and lead to biomass reductions or even root death?  The answer was a resounding no.  After 45 days of growth at 10,000 ppm CO2, for example, root dry weight was increased by fully 37% relative to the dry weight of roots produced in bioreactors in equilibrium with normal ambient air, while root dry mass was increased by a lesser 27% after 45 days at 25,000 ppm CO2 and by a still smaller 9% after 45 days at 50,000 ppm CO2.  Hence, although the optimum CO2 concentration for ginseng root growth clearly resided at some value lower than 10,000 ppm in this study, the concentration at which root growth rate was reduced below that characteristic of ambient air was somewhere significantly above 50,000-ppm, for even at that high CO2 concentration, root growth was still greater than it was in ambient air.

Almost everything else measured by Ali et al. was even more dramatically enhanced by the ultra-high CO2 concentrations they employed in their experiment.  After 45 days of treatment, total root phenolic concentrations were 58% higher at 10,000 ppm CO2 than at ambient CO2, 153% higher at 25,000 ppm CO2 and 105% higher at 50,000 ppm CO2, as best we can determine from the bar graphs of their results.  Likewise, total root flavonoid concentrations were enhanced by 228%, 383% and 232%, respectively, at the same ultra-high CO2 concentrations, while total protein contents rose by 14%, 22% and 30%, non-protein thiol contents by 12%, 43% and 62%, and cysteine contents by 27%, 65% and 100% under the identical respective set of conditions.  What is more, there were equally large CO2-induced increases in the activities of a large number of phenol biosynthetic enzymes.

What are the implications of these results?  Ali et al. write that "the consumption of foodstuffs containing antioxidant phytonutrients such as flavonoids, polyphenolics, ascorbate, cysteine and non-protein thiol is advantageous for human health," citing Cervato et al. (2000) and Noctor and Foyer (1998).  Hence, they conclude that their technique for the culture of ginseng roots in CO2-enriched bioreactors could be used for the large-scale production of an important health-promoting product that could be provided to the public in much greater quantities than is currently possible.

We further note that as the air's CO2 content continues to climb, ginseng and many other medicinal plants will likely see the concentrations of their health-promoting carbon-based secondary compounds naturally increased, leading to better human health the world over.  In fact, this phenomenon has likely played a role (the magnitude of which is yet to be determined) in the huge lengthening of human life span that occurred over the course of the Industrial Revolution, when the air's CO2 concentration rose from something on the order of 280 ppm to a value that is currently close to 380 ppm.

Sherwood, Keith and Craig Idso

Ali, M.B., Hahn, E.J. and Paek, K.-Y.  2005.  CO2-induced total phenolics in suspension cultures of Panax ginseng C.A. Mayer roots: role of antioxidants and enzymes.  Plant Physiology and Biochemistry 43: 449-457.

Cervato, G., Carabelli, M., Gervasio, S., Cittera, A., Cazzola, R.. and Cestaro, B.  2000.  Antioxidant properties of oregano (Origanum vulgare) leaf extracts.  Journal of Food Biochemistry 24: 453-465.

Gillis, C.N.  1997.  Panax ginseng pharmacology: a nitric oxide link?  Biochemical Pharmacology 54: 1-8.

Noctor, G. and Foyer, C.H.  1998.  Ascorbate and glutathione: keeping active oxygen under control.  Annual Review of Plant Physiology and Plant Molecular Biology 49: 249-279.