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Submitted to: International Journal of Plant Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/15/2001 Publication Date: 12/1/2001 Citation: Bunce, J.A. 2001. Are annual plants adapted to the current atmospheric concentration of carbon dioxide?. International Journal of Plant Science. 162:1261-1266. Interpretive Summary: The concentration of carbon dioxide in the atmosphere has risen from about 280 parts per million in 1870 to about 370 ppm currently, and continues to increase rapidly. In planning for future, higher atmospheric concentrations of carbon dioxide, the question arises whether genetic modifications of crop plants are required in order to fully exploit the increased availability of this often growth-limiting resource. Based on the concept that adaptation to a given resource level is reflected in how the efficiency with which plants use a resource changes with the availability of that resource, we examined various aspects of plant growth responses to carbon dioxide from slightly below too slightly above the current atmospheric concentration. By several measures, the efficiency at which plants used carbon dioxide decreased abruptly just above the current atmospheric concentration of carbon dioxide. These responses suggest that these species are adapted to the current atmospheric concentration of carbon dioxide, but not to higher concentrations. This implies that selection of crop plants for increased growth at elevated carbon dioxide would be effective. This information will be of use to crop breeders in developing crops with a high yield under the atmospheric conditions expected in the near future. Technical Abstract: The concentration of carbon dioxide in the atmosphere has risen from about 280 ppm in 1870 to about 370 ppm currently, and continues to increase rapidly. In planning for future, higher atmospheric concentrations of carbon dioxide, the question arises whether genetic modifications of crop plants are required in order to fully exploit the increased availability of this often growth-limiting resource, and also whether genetic changes are likely to result from natural selection in non crop species as atmospheric carbon dioxide increases. Based on the concept that adaptation to a given resource level is reflected in how resource use efficiency changes with the availability of that resource, we examined various aspects of plant growth response to carbon dioxide from 90 ppm below to 90 ppm above the current atmospheric concentration in four annual species. By several measures, the efficiency at which plants used carbon dioxide decreased abruptly just above the current atmospheric concentration of carbon dioxide. For example, total plant leaf area increased up to, but not above the current concentration, and leaf area per unit of plant dry mass was constant up to the current concentration and decreased at higher concentrations. Down-regulation of photosynthesis occurred in three of the four species when grown above the current concentration. These responses suggest that these annual species are adapted to the current atmospheric concentration of carbon dioxide. |
