What was done
The authors grew 16 genotypes of rice (Oryza sativa L.) under standard lowland paddy culture with adequate water and nutrients at the Rice Research and Development Institute in Sri Lanka from May to August (the yala season) and from November to March (the maha season) within open-top chambers maintained at either the ambient atmospheric CO2 concentration (370 ppm) or at an elevated CO2 concentration (570 ppm).
What was learned
De Costa et al. report that the CO2-induced enhancement of the light-saturated net photosynthetic rates of the 16 different genotypes during the grain-filling period of growth ranged from +2% to +185% in the yala season and from +22% to +320% in the maha season. Likewise, they found that the CO2-induced enhancement of the grain yields of the 16 different genotypes ranged from +4% to +175% in the yala season and from -5% to +64% in the maha season.
What it means
The five Sri Lanka researchers say their results "demonstrate the significant genotypic variation that exists within the rice germplasm, in the response to increased atmospheric CO2 of yield and its correlated physiological parameters," and they go on to suggest that "the significant genotypic variation in this response means that genotypes that are highly responsive to elevated CO2 may be selected and incorporated into breeding programs to produce new rice varieties which would be higher yielding in a future high CO2 climate," whereas Idso and Idso (2000) had merely calculated the increase in yield expected to result from projected increases in the air’s CO2 content for existing crop varieties. The latter of these critically important benefits will occur automatically; but to achieve the benefits envisioned by De Costa et al. – and to avert the biological catastrophe foreseen by the scientists cited in the background section of this review – will require that the breeding programs De Costa et al. propose be initiated as soon as possible.
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Reviewed 1 August 2007