How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Atmospheric CO2 Enrichment of a Pair of Medicinal Plants
Stutte, G.W., Eraso, I. and Rimando, A.M. 2008. Carbon dioxide enrichment enhances growth and flavonoid content of two Scutellaria species. Journal of the American Society for Horticultural Science 133: 631-638.

The authors write that "many Scutellaria species are rich in physiologically active flavonoids that have a wide spectrum of pharmacological activity," noting that leaf extracts of Scutellaria barbata "have been used in traditional Chinese medicine to treat liver and digestive disorders and cancers (Molony and Molony, 1998)," and that "recent research has shown extracts of S. barbata to be limiting to the growth of cell lines associated with lung, liver, prostate and brain tumors (Yin et al., 2004)."

What was done
Stutte et al. grew S. barbata and S. lateriflora plants from seed in large walk-in controlled environment chambers -- which were maintained at atmospheric CO2 concentrations of either 400, 1200 or 3000 ppm -- to the time of flowering (35 days after planting), as well as the time of seed drop (49 days after planting), after which the plants were harvested, their fresh and dry weights were determined, and the concentrations of a host of plant flavonoides within their tissues were measured.

What was learned
At 49 days after planting, the shoot dry weight of S. barbata was found to have increased by 54% at 1200 ppm CO2 and by 57% at 3000 ppm CO2, while that of S. lateriflora had increased by 44% and 70%, respectively, under the same CO2 concentrations. In addition, the average concentration of the six flavonoids the researchers measured was increased by 48% at 1200 ppm CO2 and by 81% at 3000 ppm CO2 in the vegetative tissues of S. barbata, while it was increased by more than 2.4-fold at 1200 and 4.9-fold at 3000 ppm CO2 in S. lateriflora. Therefore, Stutte et al. report that in the case of S. lateriflora, "there was a 4.2-fold increase in total flavonoid content when enriching from 400 to 1200 ppm CO2, and a 13.7-fold increase at 3000 ppm." And they state that "these results are generally consistent with those of B. Schmidt, W.D. Clark and S.B. Idso (unpublished data) who grew S. baicalensis at 700 ppm CO2," and who found that "total dry biomass was increased significantly" and that "the overall antioxidant capacity, based on the ferric reducing antioxidant power assay, was increased."

What it means
The three researchers say that "these results clearly demonstrate the potential to use controlled environments to increase the production and quality of Scutellaria species ... because the practice has the potential to increase the value of the product by reducing the time to harvest, increasing yield per unit area, and increasing bioactivity per gram of dry matter." Likewise, the extremely positive results hint at the likelihood that the active ingredients of many other medicinal plants may be similarly enhanced by atmospheric CO2 enrichment, and that the historical rise in the air's CO2 content may have already done much the same thing for the plants that people include in their everyday diets, which in turn may well have played a role in promoting the dramatic increase in human life span that has occurred over the past two centuries, as discussed more fully in items archived under the headings of Life Span (Human) and Health Effects (CO2 -- Health-Promoting Substances) in our Subject Index.

Molony, D. and Molony, M.M.P. 1998. The American Association of Oriental Medicines Complete Guide to Chinese Herbal Medicine. Berkley Publishing Group, New York, New York, USA.

Yin, X., Zhou, J., Jie, C., Xing, D. and Zhang, Y. 2004. Anticancer activity and mechanism of Scutellaria barbata extract on human lung cancer cell line A549. Life Sciences 75: 2233-2244.

Reviewed 3 November 2010