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Loblolly Pine Response to Ultra-High CO2 Concentrations
Tisserat, B. and Vaughn, S.F.  2003.  Ultra-high CO2 levels enhance loblolly pine seedling growth, morphogenesis, and secondary metabolism.  HortScience 38: 1083-1085.

What was done
In an attempt to determine if short but high CO2-enrichment treatments might enhance the growth of loblolly pine (Pinus taeda L.) seedlings and thereby reduce seedling growing time in nurseries, the authors grew four-week-old loblolly pine seedlings for 30 days at atmospheric CO2 concentrations of 350, 1500, 3000, 10,000 and 30,000 ppm within 17.6-liter transparent containers -- where seedlings were watered three times per week but not fertilized -- once a year for a total of three years.

What was learned
Tisserat and Vaughn report that the "fresh weight of seedlings, needles per seedling, roots per seedling, and shoot length in loblolly pine seedlings increased 341%, 200%, 74%, and 75%, respectively, after 30 d exposure to 10,000 [ppm] CO2 over those obtained from seedlings grown [at] ambient CO2 levels," but that there were no further increases - or decreases - when going from an atmospheric CO2 concentration of 10,000 ppm to one of 30,000 ppm.  In addition, they report that "associated with increased growth and morphogenesis is a corresponding increase in secondary metabolites [more than 99% of which were α- and β-pinene] in the ultra-high CO2 environments."

What it means
The pair of USDA scientists did indeed demonstrate that short but high CO2-enrichment treatments tremendously enhance the growth of loblolly pine seedlings, which should significantly reduce the time they need to grow to transplant size in nurseries.  In addition, they note that "high α- and β-pinene levels may confer an additional positive survival advantage " on the seedlings, since these substances "have fungicidal and insecticidal activity (Harbone, 1982; Klepzig et al., 1995)."  Last of all, we note that these findings -- plus the others that are listed under the heading Growth Response to Very High CO2 Concentrations in our Subject Index -- tend to confirm the benefits of very high atmospheric CO2 levels for earth's plants in general, augmenting the earlier findings of Tisserat et al. (1997) that "ultra-high CO2 levels enhance in vitro growth in several C-3 photosynthesis species."

Harbone, J.B.  1982.  Introduction to Ecological Biochemistry.  Academic Press, New York, NY, USA.

Klepzig, K.D., Kruger, E.L., Smalley, E.B. and Raffa, K.F.  1995.  Effects of biotic and abiotic stress on induced accumulation of terpenes and phenolics in red pines inoculated with bark beetle-vectored fungus.  Journal of Chemical Ecology 21: 601-625.

Tisserat, B., Herman, C., Silman, R. and Bothast, R.J.  1997.  Using ultra-high carbon dioxide levels enhances plantlet growth in vitro.  HortTechnology 7: 282-289.

Reviewed 28 July 2004