Photosynthetic acclimation to elevated atmospheric CO2 concentration in the Florida scrub-oak species Quercus geminata and Quercus myrtifolia growingin their native environment

Long-term effects of elevated CO2 concentration (ambient plus 350 mu mol mo l(-1)) on leaf photosynthetic acclimation of two species of a scrub-oak com munity, Quercus myrtifolia Willd. and Quercus geminata Small, were studied. Plants of both species were grown in open-top chambers in their natural ha bitat at Kennedy Space Center, Florida, USA. Compared to ambient CO2, eleva ted CO2 stimulated photosynthetic rates by 73 and 51% for Q. geminata and Q . myrtifolia, respectively. Maximum rate of carboxylation (V-cmax) was sign ificantly reduced by elevated CO2 in Q. myrtifolia (28%) but not in Q. gemi nata. Maximum rate of potential electron transport (J(max)) was not signifi cantly reduced by elevated CO2 in either species. In response to elevated C O2, specific leaf area decreased in Q, myrtifolia (22%), but not in Q. gemi nata. Elevated CO:! caused a significant accumulation of sugars (54%) and s tarch (264%) in Q, myrtifolia leaves, but not in Q. geminata leaves. Total Rubisco activity in Q. myrtifolia leaves was reduced 40% by elevated CO2, w hereas no significant reduction occurred in Q, geminata leaves. Although bo th species share a common habitat, they exhibited marked differences in pho tosynthetic acclimation to elevated CO2 concentration.