2004 Denver Annual Meeting (November 7–10, 2004)

Paper No. 40
Presentation Time: 8:00 AM-12:00 PM


DECHERD, Sara M.1, PIANTADOSI, Claude A.2, GOLDFARB, Barry3, WHEELER, Elisabeth4, BARRICK, Reese5, SCHWEITZER, Mary H.1 and RUSSELL, Dale A.6, (1)Department of Marine, Earth and Atmospheric Sciences, North Carolina State Univ, Box 8208, Raleigh, NC 27695, (2)Center for Hyperbaric Medicine and Environmental Physiology, Duke Univ, Box 3315 Duke South Hospital, Trent Drive, Durham, NC 27710, (3)Department of Forestry, North Carolina State Univ, Box 8002, Raleigh, NC 27695-8002, (4)Wood & Paper Science, N.C. State Univ, Box 8005, Raleigh, NC 27695-8005, (5)College of Eastern Utah Prehistoric Museum, Price, UT 84501, (6)North Carolina Museum of Natural Sciences, Raleigh, NC 27695, smdecher@unity.ncsu.edu

Recent experimental studies on the photosynthetic rate, stomatal density and stomatal index of Ginkgo biloba have been effective in reconstructing paleo-CO2 levels. However, few experimental studies have examined other environmental factors that can affect photosynthesis and stomatal frequency. Photosynthetic rate, stomatal index, and stomatal density data were collected from plants after experimental exposure to atmospheric content treatments within hyperbaric chambers at Duke University Medical Center (Durham, NC). Treatments include:
    1. Control: no atmospheric alteration
    2. Pressure: atmospheric pressure increased to 1.25 atm, but gas mix unaltered
    3. CO2: atmospheric pressure increased to 1.25 atm, CO2 increased to 2000 ppm
    4. O2: atmospheric pressure increased to 1.25 atm, O2 increased to 30%
    5. CO2&O2: atmospheric pressure increased to 1.25 atm, CO2 increased to 2000 ppm, and O2 increased to 30%

Photosynthetic rate data were collected after a 24-hour acclimation period in all treatments, and after 1 month of acclimation for treatments A, C, and E. Stomatal density and stomatal index were measured from leaves formed under exposure to treatments A, C, and E.

Preliminary photosynthetic rate data indicate two interesting results: (1) increased CO2 increased photosynthetic rate by a factor of 2 to 3, and (2) elevated oxygen, contrary to previous research, did not significantly inhibit photosynthesis at ambient CO2. Both long and short acclimation periods gave similar gas exchange results. Stomatal density and index showed an unexpected positive relationship with CO2, as well as a lack of significant oxygen effect. Future studies will examine additional replications of the gas composition treatments to verify gas exchange and stomatal results and will examine the effects of these treatments on the chemical composition of leaves produced under the different gas conditions.