|Allen, Leon - Hartwell|
Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/1998
Publication Date: N/A
Citation: Interpretive Summary: Atmospheric carbon dioxide (CO2) concentrations are increasing, and these increases could have important influences on plant growth. Increases in CO2 are also projected to influence other aspects of the climate including rainfall patterns. Since inadequate rainfall is the most common limitation on crop yield, it is important to know what will be the response of crops to drought under increased atmospheric CO2. This study, by scientists with USDA, Agricultural Research Service in Gainesville, FL, was designed to document the response in soybean of plant transpiration, leaf photosynthesis, and leaf area development to drought under increased CO2. The results of this experimentation showed that the inherent plant responses to soil drying were not changed by increased CO2. These results indicated that previous understandings of basic plant vulnerability to drought will not be changed by the increase in CO2, and that past information concerning these processes is fully applicable to global environment change.
Technical Abstract: Projected climate changes associated with current increases in global atmospheric CO2 may result in shifts in precipitation patterns and increased drought. This study was conducted to determine the response of soybean (Glycine max Merr.) to the combined effects of water deficits and CO2 enrichment. The main objective was to characterize leaf growth and gas exchange as functions of soil water content. Four-week old plants were transferred into two greenhouses with either ambient (360 umol mol-1) or elevated CO2 (700 umol mol-1). Following a 2-day acclimation period, the soil of the drought-stressed pots was allowed to dry slowly over a 17-d period. The stressed pots were watered daily so that the soil dried at an equivalent rate under the two CO2 levels. Elevated CO2 decreased water loss rate and increased leaf area development and photosynthetic rate under both well-watered and drought- stressed conditions. There was, however, no significant effect of CO2 on the relative response to soil water content of normalized leaf gas exchange and leaf area. Thus, drought response functions provide an effective method for describing the responses of soybean physiological processes to the available soil water, independent of CO2.