Synergistic Effects of Elevated CO2 and 03 on Stomatal Conductance and Photosynthetic Pathway

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Both C02 and 03 have profound effects on plant growth, physiology and biochemistry. Given that levels of each gas are increasing and will continue to increase, this may result in substantial impact on the function and productivity of plants in natural and agroecosystems. Research is proposed on the interactive effects of elevated levels of both C02 and 03 on six perennial canopy dominants of the forests and prairies of the Midwest. The study species differ in intrinsic characteristics that may result in differing response to atmospheric pollutants. The species differ in growth form stomatal conductance and photosynthetic pathway. The investigators will test the hypothesis that elevated levels of C02 will partially ameliorate the deleterious effects of 03. They will also test a number of other hypotheses relating growth form, stomatal conductance and photosynthetic pathway to pollutant response. In general, among all species, if there are significant interactions between 03 and C02, rather than a strictly additive combined response, this will suggest that the impacts of continued elevation of the atmospheric concentrations of these two gases on plant physiological behavior may be exceedingly complex and difficult to either predict or monitor. The results of this research will be important to our basic understanding of the relationships of certain physiological "life history" traits to a changing atmospheric environment. In addition, they should help focus our national policy and research priorities by adding to the small but growing data base addressing the response of natural systems to a rapidly shifting atmospheric composition.