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Response of Second- and Third-Generation Wheat Plants to Elevated CO2
Derner, J.D., Tischler, C.R., Polley, H.W. and Johnson, H.B.  2004.  Intergenerational above- and belowground responses of spring wheat (Triticum aestivum L.) to elevated CO2Basic and Applied Ecology 5: 145-152.

What was done
The authors determined above- and below-ground responses of three generations of two genotypes of spring wheat to atmospheric CO2 enrichment to 336 ppm above ambient.  Their experiment was conducted in glasshouse bays, where the second- and third-generation plants were progeny of seeds produced by plants grown at either ambient or enriched atmospheric CO2 concentrations under well-watered and high soil-nutrient conditions.

What was learned
Surprisingly, neither genotype in the first generation exhibited enhanced growth in response to the increased concentration of atmospheric CO2.  However, Derner et al. report that "relative enhancement occurred in both the second and third generations for both above- and below-ground variables," and that the "relative enhancement of measured variables was generally greater in the third than second generation when plants were in the seedling or vegetative stage [our italics]."  They also determined that "intergenerational above- and below-ground responses of this C3 annual plant to CO2 enrichment are not driven by genetic change (selection) that occurred between generations, but rather CO2-induced changes in seeds that affected seedling responses to CO2 enrichment."

What it means
Because, in the words of the authors, "there is a paucity of information on the extent to which plants show intergenerational differences in their response to elevated CO2," it is probably too early to say much about the implications of these findings, other than to suggest that many more such studies should be undertaken to fill this important research gap, especially since the few studies that have been conducted "indicate that elevated CO2 may differentially affect growth across generations (Curtis et al., 1996; Bezemer et al., 1998; Huxman et al., 1998; Ward et al., 2000)."

Bezemer, T.M., Thompson, L.J. and Jones, T.H.  1998.  Poa annua shows inter-generational differences in response to elevated CO2Global Change Biology 4: 687-691.

Curtis, P.S., Klus, D.J., Kalisz, S. and Tonsor, S.J.  1996.  Intraspecific variation in CO2 responses in Raphanus raphanistrum and Plantago lancelata: Assessing the potential for evolutionary change with rising atmospheric CO2.  In: Korner, C. and Bazzaz, F.A. (Eds.).  Carbon Dioxide, Populations, and Communities.  Academic Press, London, UK, pp. 13-22.

Huxman, T.E., Hamerlynck, E.P., Jordan, D.N., Salsman, K.J. and Smith, S.D.  1998.  The effects of parental CO2 environment on seed quality and subsequent seedling performance in Bromus rubensOecologia 114: 202-208.

Ward, J.K., Antonovics, J., Thomas, R.B. and Strain, B.R.  2000.  Is atmospheric CO2 a selective agent on model C3 annuals?  Oecologia 123: 330-341.

Reviewed 25 August 2004