Document: JIA-3-34-83

Are native plants exposed to elevated atmospheric CO₂ in situations more tolerant of drought than those exposed to present levels of CO₂?

LI, J.* ¹, B.A.HUNGATE ², P.DIJKSTRA ¹, R.M.WHEELER ³, C.R.HINKLE ³ and B.G.DRAKE ¹

Smithsonian Environmental Research Center, Edgewater, MD 21037 USA ¹
Northern Arizona University, Flagstaff, AZ 86011 USA ²
Kennedy Space Center, FL 32899 USA ³

Abstract:
We studied the effects of elevated atmospheric CO₂ concentration (Ca) on leaf gas exchange of Quercus myrtifolia in a Florida scrub-oak ecosystem during and after a severe drought that occurred in the spring of 1998. The drought in May reduced leaf net photosynthesis, transpiration, and stomatal conductance 62%, 56%, and 68%, respectively compared with non-drought conditions in August. A mid-day depression of photosynthesis and stomatal conductance occurred during drought but not in non-drought conditions. Elevated CO₂ increased photosynthesis and decreased stomatal conductance and transpiration more during drought than during non-drought. Net photosynthesis and transpiration were significantly correlated with stomatal conductance irrespective of drought. Elevated CO₂ reduced the marginal water cost of carbon gain by 48% under drought but had no effect in non-drought. These results show that elevated CO₂ increases drought tolerance of Quercus myrtifolia.

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This abstract is being presented at: 10:30 AM in session:
Poster Session #18: Elevated CO₂.