How will the ongoing rise in the air's CO2 content alter the amounts and concentrations of various health-promoting substances produced by medicinal or "health food" plants? This question was broached early on by Stuhlfauth et al. (1987), who found that a near-tripling of the air's CO2 content increased the dry weight production of the woolly foxglove plant (which produces the cardiac glycoside digoxin used in the treatment of cardiac insufficiency) by 63% under dry conditions and by 83% when well-watered, and that the concentration of digoxin within the plant dry mass was enhanced by 11% under wellwatered conditions and by 14% under conditions of water stress, after which Stuhlfauth and Fock (1990) obtained similar results in a field study, with a near-tripling of the air's CO2 content leading to a 75% increase in plant dry weight production per unit land area and a 15% increase in digoxin per unit dry weight of plant material, which resulted in an actual doubling of total digoxin yield per hectare of cultivated land.
A full decade later, Idso et al. (2000) grew spider lily plants out-of-doors at Phoenix, Arizona in clearplastic-wall open-top enclosures that had their atmospheric CO2 concentrations maintained at either 400 or 700 ppm for two consecutive twoyear growth cycles. This work revealed that the 75% increase in the air's CO2 concentration increased aboveground plant biomass by 48% and belowground (bulb) biomass by 56%. In addition, the extra CO2 increased the concentrations of five bulb constituents possessing anticancer and antiviral properties. Mean percentage increases in these concentrations were, in the words of the researchers, "6% for a two-constituent (1:1) mixture of 7-deoxynarciclasine and 7-deoxy-transdihydronarciclasine, 8% for pancratistatin, 8% for trans-dihydronarciclasine, and 28% for narciclasine, for a mean active-ingredient percentage concentration increase of 12%." And combined with the 56% increase in bulb biomass, these percentage concentration increases resulted in a mean active-ingredient increase of 75% for the 75% increase in the air's CO2 concentration.
Why was this study so important? It was important because the substances studied had been demonstrated to be effective in fighting a number of devastating human maladies, including leukemia, ovary sarcoma, melanoma, and brain, colon, lung and renal cancers, as well as Japanese encephalitis and yellow, dengue, Punta Tora and Rift Valley fevers. And the finding that atmospheric CO2 enrichment increases both bulb biomass and the bulb concentrations of the substances that do these things bodes well for the CO2-induced stimulation of the production of still other botanical-based medicines in other plants.