How does rising atmospheric CO2 affect marine organisms?

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Stomatal Responses of Wild Radish to Elevated CO2
Case, A.L., Curtis, P.S. and Snow, A.A.  1998.  Heritable variation in stomatal responses to elevated CO2 in wild radish, Raphanus raphanistrum (Brassicaceae).  American Journal of Botany 85: 253-258.

What was done
Twelve wild radish genotypes, of varying stomatal indices and guard cell lengths, were collected in Maine, USA, and grown in greenhouses with atmospheric CO2 concentrations of 370 and 680 ppm to study the effects of elevated CO2 on stomatal characteristics and reproductive growth.

What was learned
Elevated CO2 did not significantly affect stomatal index or guard cell length.  In fact, across all genotypes investigated, leaf surface characteristics were essentially unchanged by elevated CO2.  Among genotypes, no evidence was found for differential responses to elevated CO2 in terms of growth or reproductive characteristics.  However, in this particular study, atmospheric CO2 enrichment elicited a marginally significant decrease of 17% in flower and fruit production, which is contrary to a larger database of positive yield responses for this species (Idso and Kimball, 1989; Overdieck et al. 1988; Idso et al. 1987; Morison and Gifford, 1984; Sionit et al. 1982).

What it means
As the CO2 content of the air increases, wild radish will likely maintain its current compliment of genetic diversity with respect to stomatal indices and guard cell lengths.  Because these genotypes exhibited similar reductions in flower and fruit production, it is unlikely that elevated CO2 will selectively favor one genotype over another.  Thus, wild radish diversity should persist as the atmospheric CO2 concentration rises.

Idso, S.B. and Kimball, B.A.  1989.  Growth response of carrot and radish to atmospheric CO2 enrichment.  Environmental and Experimental Botany 29: 135-139.

Overdieck, D., Reid, Ch. and Strain, B.R.  1988.  The effects of preindustrial and future CO2 concentrations on growth, dry matter production and the C/N relationship in plants at low nutrient supply: Vigna unguiculata (Cowpea), Abelmoschus esculentus (Okra) and Raphanus sativus (Radish).  Angewandte Botanik 62: 119-134.

Idso, S.B., Kimball, B.A., Anderson, M.G. and Mauney, J.R.  1987.  Effects of atmospheric CO2 enrichment on plant growth: the interactive role of air temperature.  Agriculture, Ecosystems and Environment 20: 1-10.

Morison, J.I.L. and Gifford, R.M.  1984.  Plant growth and water use with limited water supply in high CO2 concentrations.  II.  Plant dry weight, partitioning and water use efficiency.  Australian Journal of Plant Physiology 11: 375-384.

Sionit, N., Hellmers, H. and Strain, B.R.  1982.  Interaction of atmospheric CO2 enrichment and irradiance on plant growth.  Agronomy Journal 74: 721-725.

Reviewed 15 September 1999