A full decade later, Idso et al. (2000) grew spider lily plants out-of-doors at Phoenix, Arizona in clear-plastic-wall open-top enclosures that had their atmospheric CO2 concentrations maintained at either 400 or 700 ppm for two consecutive two-year 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-trans-dihydronarciclasine, 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 have 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.

A good example is the study of Zobayed and Saxena (2004), who worked with St. Johns' wort, a perennial herb native to Europe and West Asia that has been used for treatment of mild to moderate depression, inflammation and wound healing (Brolis et al., 1998; Stevinson and Ernst, 1999), and which has been reported to be a potential source for anticancer, antimicrobial and antiviral medicines (Schempp et al., 2002; Pasqua et al., 2003). In their case, they grew shoots of the plant for 42 days under well watered and fertilized conditions within a greenhouse, where the air's CO2 concentration averaged 360 ppm, as well as in computer-controlled environment chambers maintained at a mean CO2 concentration of 1000 ppm, with all other environmental conditions being comparable between the two treatments.

On the final day of the study, the researchers determined that the net photosynthetic rates of the plants in the CO2-enriched chambers were 124% greater than those of the plants growing in ambient air, and that their dry weights were 107% greater. In addition, the extra 640 ppm of CO2 in the high-CO2 treatment increased plant concentrations of hypericin and pseudohypericin (two of the major health-promoting substances in the plants) by just over 100%. Consequently, the 180% increase in the air's CO2 content more than doubled the dry mass produced by the well-watered and fertilized St. John's wort plants, while it also more than doubled the concentrations of hypericin and pseudohypericen found in their tissues, which means that the CO2 increase more than quadrupled the total production of these two health-promoting substances.

Mosaleeyanon et al. (2005) also studied St. John's wort, growing well watered and fertilized seedlings for 45 days in controlled-environment chambers at low, medium and high light intensities (100, 300 and 600 µmol m^-2 s^-1, respectively) at atmospheric CO2 concentrations of 500, 1000 and 1500 ppm. Then, on day 45 of the experiment, the plants were harvested, and the hypericin, pseudohypericin and hyperforin (another important health-promoting substance) they contained were extracted from their leaves and quantified.

Under all three light intensities employed in the study, the four researchers found that the 1000-ppm increase in atmospheric CO2 concentration experienced in going from 500 to 1500 ppm produced total plant biomass increases of approximately 32%. And over this same CO2 range, hypericin concentrations rose by 78, 57 and 53%, respectively, under the low, medium and high light intensities, while pseudohypericin concentrations rose by 70, 57 and 67%, and hyperforin concentrations rose by 102, 23 and 3%. Last of all, compared to plants growing out-of-doors in air of 380 ppm CO2 and at light intensities on the order of 1770 µmol m^-2 s^-1, Mosaleeyanon et al. report that total plant biomass was fully 30 times greater in the high-light, high-CO2 controlled-environment treatment, while under the same conditions the concentrations of hypericin and pseudohypericin were 30 and 41 times greater. Thus, the researchers demonstrated that growing St. John's wort plants in CO2-enriched air in controlled-environment chambers can enormously enhance both plant biomass and hypericin and pseudohypericin contents.

In a concurrent study, Ziska et al. (2005) grew well watered and fertilized tobacco and jimson weed plants from seed in controlled-environment chambers maintained at atmospheric CO2 concentrations of either 378 ppm (ambient) or 690 ppm (elevated) and mean air temperatures of either 22.1 or 27.1°C for 50 and 47 days after planting for tobacco and jimson weed, respectively, while sampling the plants at weekly intervals beginning at 28 days after planting for tobacco and 16 days for jimson weed, in order to determine the effects of these treatments on three plant alkaloids possessing important pharmacological properties: nicotine, in the case of tobacco, and atropine and scopolamine, in the case of jimson weed. And in following these protocols, they found that at the time of final harvest the elevated CO2 had increased the aboveground biomass production of tobacco by approximately 89% at 22.1°C and 53% at 27.1°C, and to have increased that of jimson weed by approximately 23% and 14% at the same respective temperatures. The extra CO2 was also found to have reduced the concentration of nicotine in tobacco, increased the concentration of scopolamine in jimson weed, but to have had no significant effect on the concentration of atropine in jimson weed.

The two significant changes (reduced nicotine in tobacco and increased scopolamine in jimson weed) would likely be characterized as beneficial by most people; for the six scientists report that nicotine is acknowledged to have significant negative impacts on human health, and that scopolamine is used as a sedative and as "an antispasmodic in certain disorders characterized by restlessness and agitation, (e.g., delirium tremens, psychosis, mania and Parkinsonism)." Nevertheless, Ziska et al. say "it can be argued that synthetic production of these secondary compounds alleviates any concern regarding environmental impacts on their production from botanical sources," but they add that "developing countries (i.e., ~75% of the world population) continue to rely on ethno-botanical remedies as their primary medicine (e.g. use of alkaloids from jimson weed as treatment for asthma among native Americans and in India)," also noting that "for both developed and developing countries, there are a number of economically important pharmaceuticals derived solely from plants whose economic value is considerable (Raskin et al., 2002)."

Another plant with an impressive history of medicinal use is the ginseng plant. Well known for its anti-inflammatory, diuretic and sedative properties, and long acknowledged to be an effective healing agent (Gillis, 1997), ginseng is widely cultivated in China, South Korea and Japan, where it has been used for medicinal purposes since Greek and Roman times. Normally, 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. (2005) investigated the consequences of growing ginseng plants in suspension culture in bioreactors maintained in equilibrium with air 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, root dry weight was increased by about 37% relative to the dry weight of roots produced in bioreactors in equilibrium with ambient air, while it 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. Consequently, although the optimum CO2 concentration for ginseng root growth likely resides somewhere below 10,000 ppm, the concentration at which root growth is reduced below that characteristic of ambient air resides somewhere above 50,000 ppm, for even at that extremely 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, in this regard, that as the air's CO2 content continues to climb, ginseng and other medicinal plants will likely see the concentrations of their health-promoting substances naturally increased, leading to better human health the world over. This phenomenon, in fact, has likely already played a role (the magnitude of which is yet to be determined) in the huge lengthening of human life span that has occurred since the dawn of the Industrial Revolution, as described by Horiuchi (2000) and Tuljapurkar et al. (2000), during which time the air's CO2 concentration rose from something on the order of 280 ppm to its current value of approximately 390 ppm.

Another plant that serves as both a health-promoting food and a food delicacy (in China, Japan and Korea) is the brown seaweed Hizikia fusiforme, which was studied by Zou (2005), who collected specimens of it from intertidal rocks along the coast of Nanao Island, Shantou (China) and maintained them in glass aquariums in filtered natural seawater enriched with 60 µM NaNO3 and 6.0 µM NaH2PO4, where the plants were continuously aerated with either ambient air of 360 ppm CO2 or CO2-enriched air of 700 ppm CO2, while Zou measured the seaweed's relative growth and nitrogen assimilation rates, as well as its nitrate reductase activity. This work revealed that the slightly less than a doubling of the air's CO2 concentration increased the seaweed's mean relative growth rate by about 50%, its mean rate of nitrate uptake during the study's 12-hour light periods by some 200%, and its nitrate reductase activity by approximately 20% over a wide range of substrate nitrate concentrations.

In discussing the implications of these findings, Zou noted that "the extract of H. fusiforme has an immunomodulating activity on humans and this ability might be used for clinical application to treat several diseases such as tumors (Suetsuna, 1998; Shan et al., 1999)." He also wrote that the alga is "becoming one of the most important species for seaweed mariculture in China, owing to its high commercial value and increasing market demand," and it would seem that the ongoing rise in the air's CO2 content would bode well for both of these applications. In addition, Zou says "the intensive cultivation of H. fusiforme would remove nutrients more efficiently with the future elevation of CO2 levels in seawater, which could be a possible solution to the problem of ongoing coastal eutrophication," which in turn suggests that rising atmospheric CO2 concentrations may additionally assist in the amelioration of this important environmental problem.

Also working with a marine alga -- specifically, unicellular Nannochloropsis sp. -- were Hoshida et al. (2005), who grew the alga in batch culture under normal (370 ppm) and elevated (3,000 and 20,000 ppm) air CO2 concentrations in an attempt to learn how elevated CO2 impacted the alga's ability to produce eicosapentaenoic acid (EPA), which is a major polyunsaturated omega-3 fatty acid that may play an important role in human health related to the prevention of certain cardiovascular diseases (e.g. atherosclerosis, thrombogenesis) and the inhibition of tumor growth and inflammation, as described by Dyerberg et al. (1978), Hirai et al. (1989), Kinsella et al. (1990) and Sanders (1993). In addition, the five researchers remark that "Nitsan et al. (1999) showed that supplementing the diet of hens with Nannochloropsis sp. led to an increased content of n-3 fatty acids in the egg yolk, indicating an additional role in enhancing the nutritional value of eggs," and they say "feeding Nannochloropsis sp. to rats caused a significant increase in the content of n-3 polyunsaturated fatty acids (Sukenik et al., 1994)," suggesting that the alga may play an "important role as the source for n-3 polyunsaturated fatty acids in human nutrition."

But to return to their experiment, what the Japanese scientists found was that "maximum EPA production was obtained when 20,000 ppm CO2 was supplied 12 hours prior to the end of the exponential growth," and that "total EPA production during 4-day cultivation was about twice that obtained with ambient air." They also report that other researchers have obtained similar results, noting that EPA is found mainly in thylakoid membranes (Sukenik et al., 1989; Hodgson et al., 1991), and that prior experiments have shown that "the amount of stroma thylakoid membrane increased in several plants under elevated CO2 concentrations (Griffin et al., 2001)." In addition, they say that "in Synechococcus lividus, reduction and synthesis of thylakoid membrane occurred by CO2 deprivation and elevation, respectively (Miller and Holt, 1977)," and that "in Chlorella vulgaris, altering the ambient CO2 concentration varied fatty acid composition (Tsuzuki et al., 1990)."

Last of all, Hoshida et al. say that "the effect of CO2 on fatty acid composition and/or fatty acid content was reported in algae and higher plants (Tsuzuki et al., 1990; Sergeenko et al., 2000; He et al., 1996; Radunz et al., 2000)," and that "increased EPA production caused by elevated CO2 concentration was reported in P. tricornutum (Yongmanitchai and Ward, 1991)." Consequently, as the air's CO2 concentration continues to rise, we can expect concentrations of omega-3 fatty acids to be widely enhanced in both aquatic and terrestrial plants, thereby benefiting much of the animal life of the planet.

Three years later, Ziska et al. (2008) noted that "among medicinal plants, the therapeutic uses of opiate alkaloids from poppy (Papaver spp.) have long been recognized," and they wrote that they felt it was important "to evaluate the growth and production of opiates for a broad range of recent and projected atmospheric carbon dioxide concentrations," which they thus proceeded to do for the wild poppy (P. setigerum), growing well watered and fertilized plants from seed within growth chambers maintained at atmospheric CO2 concentrations of 300, 400, 500 and 600 ppm for a period of 90 to 100 days, while quantifying plant growth and the production of the alkaloids morphine, codeine, papaverine and noscapine, which were derived from latex obtained from capsules produced by the plants.

The three researchers' data indicated that relative to the plants grown at 300 ppm CO2, those grown at 400, 500 and 600 ppm produced approximately 200, 275 and 390% more aboveground biomass, respectively, as best we can determine from their bar graphs. In addition, they report that "reproductively, increasing CO2 from 300 to 600 ppm increased the number of capsules, capsule weight and latex production by 3.6, 3.0 and 3.7 times, respectively, on a per plant basis," with the ultimate result that "all alkaloids increased significantly on a per plant basis." Hence, they concluded that "as atmospheric CO2 continues to increase, significant effects on the production of secondary plant compounds of pharmacological interest (i.e. opiates) could be expected," which effects, in their words, "are commonly accepted as having both negative (e.g. heroin) and positive (e.g. codeine) interactions with respect to public health," with the obvious hope that the positive effects -- which are determined by people -- would prevail.

About the same time, Stutte et al. (2008) conducted a study of Scutellaria plants, which they describe as herbaceous perennials that are "rich in physiologically active flavonoids that have a wide spectrum of pharmacological activity." As one example, they note that leaf extracts of Scutellaria barbata have been found "to be limiting to the growth of cell lines associated with lung, liver, prostate, and brain tumors (Yin et al., 2004)," and that in another case "extracts of S. lateriflora and the isolated flavonoids from the extracts have been shown to have antioxidant, anticancer, and antiviral properties (Awad et al., 2003)." Hence, it is only natural that they would wonder how the growth of these plants -- and their significant medicinal components -- might be affected by the ongoing rise in the air's CO2 content.

In an attempt to shed further light on the subject, the three researchers studied both S. barbata and S. lateriflora, measuring effects of elevated atmospheric CO2 concentrations (1200 and 3000 ppm vs. a control value of 400 ppm) on total plant biomass production and plant concentrations of six bioactive flavonoids -- apigenin, baicalin, baicalein, chrysin, scutellarein and wogonin -- all of which substances, in their words, "have been reported to have anticancer and antiviral properties," as described in the review papers of Joshee et al. (2002) and Cole et al. (2007). These experiments were conducted in a large step-in controlled-environment chamber that provided a consistent light quality, intensity and photoperiod to six smaller plant growth chambers that had "high-fidelity control of relative humidity, temperature, and CO2 concentration," each of which chambers was also designed to monitor nutrient solution uptake by six individual plants that they grew from seed for a period of 49 days.

With respect to plant productivity, the U.S. researchers determined that in the case of S. barbata, increasing the air's CO2 concentration from 400 to 1200 ppm resulted in a 36% increase in shoot fresh weight and a 54% increase in shoot dry matter, with no further increases between 1200 and 3000 ppm CO2. In the case of S. lateriflora, on the other hand, the corresponding increases in going from 400 to 1200 ppm CO2 were 62% and 44%, while in going all the way to 3000 ppm CO2, the total increases were 122% and 70%, respectively.

With respect to flavonoid concentrations in the plants' vegetative tissues, Stutte et al. report that in the case of S. barbata, "the combined concentration of the six flavonoids measured increased by 48% at 1200 and 81% at 3000 ppm CO2," while in S. lateriflora they say "the total flavonoid content increased by over 2.4 times at 1200 and 4.9 times at 3000 ppm CO2." Thus, in consequence of the compounding effect of increases in both plant biomass and flavonoid concentration, the total flavonoid content in S. barbata rose by 72% in going from 400 to 1200 ppm CO2, and by 128% in going all the way to 3000 ppm CO2, while in S. lateriflora the corresponding increases were a huge 320% and a mind-boggling 1,270%.

In the concluding sentence of their paper's abstract, Stutte et al. say their results indicate that "the yield and pharmaceutical quality of Scutellaria species can be enhanced with controlled environment production and CO2 enrichment," and massively so, we would add. In addition, since they indicate that over 200 substances -- of which over 80% are flavonoids -- have been found in a total of 65 Scutellaria species, it would appear that the "increased concentration of flavonoids through CO2 enrichment," as they describe it, "has the potential to enhance the production and quality of [many, we would add] medicinal plants."

Shortly thereafter, Vurro et al. (2009) wrote that thyme (a well-known culinary and medicinal herb) has "a considerable economic value in the nutraceutical and pharmaceutical industry (Vardar-Uenlue et al., 2003; Konyalioglu et al., 2006)," and that "thyme essential oil possesses per se considerable antioxidant capacity (Economou et al., 1991), and may therefore contribute towards the control of antioxidant status in the leaves." Thus, they grew well-watered one-year-old thyme plants for three additional months (10 June - 10 September) in pots (filled with 40% sand, 25% clay and 35% silt) out-of-doors within a mini-FACE (free-air CO2-enrichment) system at Ravenna, Italy, where the air's CO2 concentration was maintained at approximately 500 ppm (during daylight hours only), and where control plants were continuously exposed to air of approximately 370 ppm CO2, while they measured a number of plant characteristics at the ends of each of the three months of the study.

In reporting their findings, the four researchers state that "none of the plants grown under high levels of CO2 for 90 days presented either significant differences in fresh weight and dry weight compared with controls, or macroscopic alteration of morphogenesis (number and length of nodes/internodes, branching, leaf area and chlorosis, etc.), at any of the sampling times." However, they did find that "in plants grown under elevated CO2, a relative increase in oil yield of 32, 34 and 32% was, respectively, recorded in the first, second and third sampling-time (July, August and September)," and they observed a "general depression of the oxidative stress under elevated CO2" that led to a "down-regulation of leaf reactive oxygen species-scavenging enzymes under elevated CO2." In layman's terms, therefore, the Italian scientists say their results point to "a 'low cost' life strategy for growth under elevated CO2, not requiring synthesis/activation of energy-intensive and expensive metabolic processes," and this change in behavior should allow the plants to invest more energy in the production of essential plant oils that have, as they have described it, "considerable economic value in the nutraceutical and pharmaceutical industry."

Last of all, and in introducing their study of the subject, Oliveira et al. (2010) say "there is a growing interest in the use of inulin as a health food ingredient, as an alternative for low-calorie sweeteners, and as a dietary fiber and fat substitute (Ritsema and Smeekens, 2003)." In addition, they say "it is suggested" that a daily intake of low amounts of inulin or its derivatives promote the growth of beneficial bacteria in the intestinal tract, as well as anti-tumor effects, citing Roberfroid (2005). Hence, they decided to study Vernonia herbacea, a plant from the Brazilian Cerrado that accumulates inulin-type fructans in underground organs called rhizophores.

The five Brazilian researchers grew well watered and fertilized V. herbacea plants from rhizophore fragments for two months and then transferred them -- in groups of three -- to 3-L pots containing forest soil, after which they were maintained in open-top chambers within a glasshouse for 120 days at atmospheric CO2 concentrations of either 380 or 760 ppm, where they measured their net photosynthetic rates, water use efficiencies and fructan concentrations after 15, 30, 60, 90 and 120 days of treatment, as well as above- and below-ground biomass at the end of the experiment.

This work revealed, in the words of Oliveira et al., that the "plants under elevated CO2 presented increases in height (40%), photosynthesis (63%) and biomass of aerial (32%) and underground (47%) organs when compared with control plants." In addition, they state that "water use efficiency was significantly higher in treated plants, presenting a 177% increase at day 60." However, they found that fructan concentration remained unchanged; but because of the significant CO2-induced increase in underground organ biomass, they write that "a 24% increase in total fructan yield occurred." And because of that fact, plus the great increase in water use efficiency displayed by the plants, a CO2-enriched future would appear to bode well for the commercial production of V. herbacea plants throughout much of the central fifth -- the Cerrado -- of Brazil.

In conclusion, it would appear that atmospheric CO2 enrichment positively impacts the production of numerous health-promoting substances found in medicinal or "health food" plants, and that this phenomenon may have contributed to the increase in human life span that has occurred over the past century or so. Therefore, as the atmosphere's CO2 content continues to rise, there is reason to believe that humanity may be helped even more in this regard in the years and decades to come.

References
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.

Awad, R., Arnason, J.T., Trudeau, V., Bergeron, C., Budziinski, J.W., Foster, B.C. and Merali, Z. 2003. Phytochemical and biological analysis of skullcap (Scutellaria lateriflora L.): A medicinal plant with anxiolytic properties. Phytomedicine 10: 640-649.

Brolis, M., Gabetta, B., Fuzzati, N., Pace, R., Panzeri, F. and Peterlongo, F. 1998. Identification by high-performance liquid chromatography-diode array detection-mass spectrometry and quantification by high-performance liquid chromatography-UV absorbance detection of active constituents of Hypericum perforatum. Journal of Chromatography A 825: 9-16.

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.

Cole, I.B., Sacena, P.K. and Murch, S.J. 2007. Medicinal biotechnology in the genus Scutellaria. In Vitro Cellular & Developmental Biology - Plant 43: 318-327.

Dyerberg, J., Bang, H.O., Stoffersen, E., Moncada, S. and Vane, J.R. 1978. Eicosapentaenoic acid and prevention of thrombosis and atherosclerosis. Lancet 2: 117-119.

Economou, K.D., Oreopoulou, V. and Thomopoulos, C.D. 1991. Antioxidant activity of some plant extracts of the family Labiatae. Journal of the American Oil Chemists' Society 68: 109-113.

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

Griffin, K.L., Anderson, O.R., Gastrich, M.D., Lewis, J.D., Lin, G., Schuster, W., Seemann, J.R., Tissue, D.T., Turnbull, M.H. and Whitehead, D. 2001. Plant growth in elevated CO2 alters mitochondrial number and chloroplast fine structure. Proceedings of the National Academy of Sciences, USA 98: 2473-2478.

He, P., Radunz, A., Bader, K.P. and Schmid, G.H. 1996. Quantitative changes of the lipid and fatty acid composition of leaves of Aleurites montana as a consequence of growth under 700 ppm CO2 in the atmosphere. Zeitschrift fur Naturforscher 51 C: 833-840.

Hirai, A., Terano, T., Tamura, Y. and Yoshida, S. 1989. Eicosapentaenoic acid and adult diseases in Japan: Epidemiological and clinical aspects. Journal of Internal Medicine, Supplement 225: 69-75.

Hodgson, P.A., Henderson, R.J., Sargent, J.R. and Leftley, J.W. 1991. Patterns of variation in the lipid class and fatty acid composition of Nannochloropsis oculata (Eustigmatophyceae) during batch culture. I. The growth cycle. Journal of Applied Phycology 3: 169-181.

Horiuchi, S. 2000. Greater lifetime expectations. Nature 405: 744-745.

Hoshida, H., Ohira, T., Minematsu, A., Akada, R. and Nishizawa, Y. 2005. Accumulation of eicosapentaenoic acid in Nannochloropsis sp. in response to elevated CO2 concentrations. Journal of Applied Phycology 17: 29-34.

Idso, S.B., Kimball, B.A., Pettit III, G.R., Garner, L.C., Pettit, G.R. and Backhaus, R.A. 2000. Effects of atmospheric CO2 enrichment on the growth and development of Hymenocallis littoralis (Amaryllidaceae) and the concentrations of several antineoplastic and antiviral constituents of its bulbs. American Journal of Botany 87: 769-773.

Joshee, N., Patrick, T.S., Mentreddy, R.S. and Yadav, A.K. 2002. Skullcap: Potential medicinal crop. In: Janick, J. and Whipkey, A. (Eds.). Trends in New Crops and New Uses. ASHS Press, Alexandria, VA, USA, pp. 58-586.

Kinsella, J.E., Lokesh, B. and Stone, R.A. 1990. Dietary n-3 polyunsaturated fatty acids and amelioration of cardiovascular diseases: Possible mechanisms. American Journal of Clinical Nutrition 52: 10-28.

Konyalioglu, S., Ozturk, B. and Meral, G.E. 2006. Comparison of chemical compositions and antioxidant activities of the essential oils of two Ziziphora taxa from Anatolia. Pharmaceutical Biology 44: 121-126.

Miller L.S. and Holt, S.C. 1977. Effect of carbon dioxide on pigment and membrane content in Synechococcus lividus. Archives Microbiologie 115: 185-198.

Mosaleeyanon, K., Zobayed, S.M.A., Afreen, F. and Kozai, T. 2005. Relationships between net photosynthetic rate and secondary metabolite contents in St. John's wort. Plant Science 169: 523-531.

Nitsan, Z., Mokady, S. and Sukenik, A. 1999. Enrichment of poultry products with omega 3 fatty acids by dietary supplementation with the alga Nannochloropsis and mantur oil. Journal of Agricultural and Food Chemistry 47: 5127-5132.

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.

Oliveira, V.F., Zaidan, L.B.P., Braga, M.R., Aidar, M.P.M. and Carvalho, M.A.M. 2010. Elevated CO2 atmosphere promotes plant growth and inulin production in the cerrado species Vernonia herbacea. Functional Plant Biology 37: 223-231.

Pasqua, G., Avato, P., Monacelli, B., Santamaria, A.R. and Argentieri, M.P. 2003. Metabolites in cell suspension cultures, calli, and in vitro regenerated organs of Hypericum perforatum cv. Topas. Plant Science 165: 977-982.

Radunz, A., Alfermann, K. and Schmid, G.H. 2000. State of the lipid and fatty acid composition in chloroplasts of Nicotiana tabacum under the influence of an increased CO2 partial pressure of 700 p.p.m. Biochemical Society Transactions 28: 885-887.

Raskin, I., Ribnicky, D.M., Komarnytsky, S. et al. 2002. Plants and human health in the twenty-first century. Trends in Biotechnology 20: 522-531.

Ritsema, T. and Smeekens, S. 2003. Fructans: beneficial for plants and humans. Current Opinion in Plant Biology 6: 223-230.

Roberfroid, M.B. 2005. Introducing inulin-type fructans. British Journal of Nutrition 93: S13-S25.

Sanders, T.A.B. 1993. Marine oils: Metabolic effects and role in human nutrition. Proceedings of the Nutrition Society 52: 457-472.

Schempp, C.M., Krikin, V., Simon-Haarhaus, G., Kersten, A., Kiss, J., Termeer, C.C., Gilb, B., Kaufmann, T., Borner, C., Sleeman, J.P. and Simon, J.C. 2002. Inhibition of tumour cell growth by hyperforin, a novel anticancer drug from St. John's wort that acts by induction of apoptosis. Oncogene 21: 1242-1250.

Sergeenko, T.V., Muradyan, E.A., Pronina, N.A., Klyachko-Gurvich, G.L., Mishina, I.M. and Tsoglin, L.N. 2000. The effect of extremely high CO2 concentration on the growth and biochemical composition of microalgae. Russian Journal of Plant Physiology 47: 632-638.

Shan, B.E., Yoshida, Y., Kuroda, E. and Yamashita, U. 1999. Immunomodulating activity of seaweed extract on human lymphocytes in vitro. International Journal of Immunopharmacology 21: 59-70.

Stevinson, C. and Ernst, E. 1999. Hypericum for depression: an update of the clinical evidence. European Neuropsychopharmacology 9: 501-505.

Stuhlfauth, T., Fock, H.P. 1990. Effect of whole season CO2 enrichment on the cultivation of a medicinal plant, Digitalis lanata. Journal of Agronomy and Crop Science 164: 168-173.

Stuhlfauth, T., Klug, K. and Fock, H.P. 1987. The production of secondary metabolites by Digitalis lanata during CO2 enrichment and water stress. Phytochemistry 26: 2735-2739.

Stutte, G.W., Eraso, I. and Rimando, A.M. 2008. Carbon dioxide enrichment enhances growth and flavoniod content of two Scutellaria species. Journal of the American Society for Horticultural Science 133: 631-638.

Suetsuna, K. 1998. Separation and identification of angiotensin I-converting enzyme inhibitory peptides from peptic digest of Hizikia fusiformis protein. Nippon Suisan Gakkaishi 64: 862-866.

Sukenik, A., Cameli, Y. and Berner, T. 1989. Regulation of fatty acid composition by irradiance level in the eustigmatophyte Nannochloropsis sp. Journal of Phycology 25: 686-692.

Sukenik, A., Takahashi, H. and Mokady, S. 1994. Dietary lipids from marine unicellular algae enhance the amount of liver and blood omega-3 fatty acids in rats. Annals of Nutrition and Metabolism 38: 85-96.

Tsuzuki, M., Ohnuma, E., Sato, N., Takaku, T. And Kawaguchi, A. 1990. Effects of CO2 concentration during growth on fatty acid composition in microalgae. Plant Physiology 93: 851-856.

Tuljapurkar, S., Li, N. and Boe, C. 2000. A universal pattern of mortality decline in the G7 countries. Nature 405: 789-792.

Vardar-Uenlue, G., Candan, F., Soekmen, A., Daferera, D., Polissiou, M., Soekmen, M., Doenmez, E. and Tepe, B. 2003. Antimicrobial and antioxidant activity of the essential oil and methanol extracts of Thymus pectinatus Fisch. et Mey var. pectinatus (Lamiaceae). Journal of Agricultural and Food Chemistry 51: 63-67.

Vurro, E, Bruni, R., Bianchi, A. and di Toppi, L.S. 2009. Elevated atmospheric CO2 decreases oxidative stress and increases essential oil yield in leaves of Thymus vulgaris grown in a mini-FACE system. Environmental and Experimental Botany 65: 99-106.

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 Science 75: 2233-2244.

Yongmanitchai, W. and Ward, O.P. 1991. Growth of and omega-3 fatty acid production by Phaeodactylum tricornutum under different culture conditions. Applied Environmental Microbiology 57: 419-425.

Ziska, L.H., Emche, S.D., Johnson, E.L., George, K., Reed, D.R. and Sicher, R.C. 2005. Alterations in the production and concentration of selected alkaloids as a function of rising atmospheric carbon dioxide and air temperature: implications for ethno-pharmacology. Global Change Biology 11: 1798-1807.

Ziska, L.H., Panicker, S. and Wojno, H.L. 2008. Recent and projected increases in atmospheric carbon dioxide and the potential impacts on growth and alkaloid production in wild poppy (Papaver setigerum DC.). Climatic Change 91: 395-403.

Zobayed, S. and Saxena, P.K. 2004. Production of St. John's Wort plants under controlled environment for maximizing biomass and secondary metabolites. In Vitro Cellular and Developmental Biology - Plant 40: 108-114.

Zou, D. 2005. Effects of elevated atmospheric CO2 on growth, photosynthesis and nitrogen metabolism in the economic brown seaweed, Hizikia fusiforme (Sargassaceae, Phaeophyta). Aquaculture 250: 726-735.