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Elevated CO2 Stimulates Cotton Boll Production In Spite of Temperature Increase
Reddy, K.K., Davidonis, G.H., Johnson, A.S. and Vinyard, B.T. 1999. Temperature regime and carbon dioxide enrichment alter cotton boll development and fiber properties. Agronomy Journal 91: 851-858.

What was done
The authors grew upland cotton (Gossypium hirsutum L.) in controlled SPAR experimental units receiving atmospheric CO2 concentrations of 360 and 720 ppm and seasonal air temperatures ranging from 2C below to 7C above ambient air temperature to study the interactive effects of elevated CO2 and air temperature on plant productivity and cotton fiber properties.

What was learned
Elevated CO2 consistently enhanced rates of net photosynthesis, producing seasonal averages that were 137 to 190% greater than averages measured for ambiently-growing plants across the entire experimental temperature range. Although elevated CO2 did not significantly impact boll size or maturation, it did increase boll numbers by about 40%, regardless of temperature treatment, without causing any changes in fiber properties.

What it means
If air temperatures in cotton-growing regions of the United States increase in future years, regardless of the cause, it is likely that the predicted rise in the air's CO2 content will still enhance cotton photosynthetic rates, boll production and fiber yields without altering fiber quality. Thus, cotton growers should not worry about dire predictions of yield loss associated with the uncertainties of possible global warming, but should rather anticipate greater marketable yields in response to demonstrated CO2-induced increases in plant productivity.