Photosynthetic Acclimation To Elevated Atmospheric CO2 Concentration In The Florida Scrub-Oak Species Quercus Geminata And Quercus Myrtifolia Growing In Their Native Environment

Long-term effects of elevated CO₂ concentration (ambient plus 350 μmol mol⁻¹) on leaf photosynthetic acclimation of two species of a scrub-oak community, Quercus myrtifolia Willd. and Quercus geminata Small, were studied. Plants of both species were grown in open-top chambers in their natural habitat at Kennedy Space Center, Florida, USA. Compared to ambient CO₂, elevated CO₂ stimulated photosynthetic rates by 73 and 51% for Q. geminata and Q. myrtifolia, respectively. Maximum rate of carboxylation (V_cmax) was significantly reduced by elevated CO₂ in Q. myrtifolia (28%) but not in Q. geminata. Maximum rate of potential electron transport (J_max) was not significantly reduced by elevated CO₂ in either species. In response to elevated CO₂, specific leaf area decreased in Q. myrtifolia (22%), but not in Q. geminata. Elevated CO₂ caused a significant accumulation of sugars (54%) and starch (264%) in Q. myrtifolia leaves, but not in Q. geminata leaves. Total Rubisco activity in Q. myrtifolia leaves was reduced 40% by elevated CO₂, whereas no significant reduction occurred in Q. geminata leaves. Although both species share a common habitat, they exhibited marked differences in photosynthetic acclimation to elevated CO₂ concentration.