How does rising atmospheric CO2 affect marine organisms?

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Response of Transgenic Rice Plants to Elevated CO2
Makino, A., Harada, M., Kaneko, K., Mae, T., Shimada, T. and Yamamoto, N.  2000.  Whole-plant growth and N allocation in transgenic rice plants with decreased content of ribulose-1,5-bisphosphate carboxylase under different CO2 partial pressures.  Australian Journal of Plant Physiology 27: 1-12.

What was done
For 70 days, the authors grew from seed three types of rice - a wild type (WT) and two transgenic varieties, one with 65% wild-type Rubisco (AS-77) and one with 40% wild-type Rubisco (AS-71) - in growth chambers maintained at 360 and 1000 ppm CO2, after which they harvested the plants and determined their biomass.

What was learned
The mean dry weights of the WT, AS-77 and AS-71 varieties grown in air of 360 ppm were, respectively, 5.75, 3.02 and 0.83 g.  In air of 1000 ppm CO2, however, the corresponding mean dry weights were 7.90, 7.40 and 5.65 g.  Hence, the CO2-induced percentage increases in plant dry weight for the three varieties were 37% (WT), 145% (AS-77) and 581% (AS-71).

What it means
Although the growth rates of the genetically-engineered rice plants were far inferior to that of the wild type when grown in normal air of 360 ppm CO2 (with AS-71 producing less than 15% as much biomass as the wild type), when grown in air of 1000 ppm CO2 they experienced far greater CO2-induced increases in growth: a 145% increase in the case of AS-77 and a whopping 581% increase in the case of AS-71.  Hence, whereas the transgenic plants were highly disadvantaged in normal air of 360 ppm CO2 (with AS-71 plants attaining a mean dry weight of only 0.83 g while the WT plants attained a mean dry weight of 5.75 g), they were found to be pretty much on an equal footing in highly-CO2-enriched air (with AS-71 plants attaining a mean dry weight of 5.65 g while the WT plants attained a mean dry weight of 7.90 g).  This finding bodes well for the application of this type of technology to crop improvement in a future world of higher atmospheric CO2 concentration.

Reviewed 5 November 2003