Stomatal acclimation to increased CO2 concentration in a Florida scrub oak species Quercus myrtifolia Willd

Native scrub-oak communities in Florida were exposed for three seasons in open top chambers to present atmospheric [CO2] (approx, 350 mu mol mol(-1)) and to high [CO2] (increased by 350 mu mol mol(-1)). Stomatal and photosynthetic acclimation to high [CO2] of the dominant species Quercus myrtifolia was examined by leaf gas exchange of excised shoots. Stomatal conductance (g(s)) was approximately 40% lower in the high- compared to low-[CO2]-grown plants when measured at their respective growth concentrations. Reciprocal measurements of g(s) in both high- and low-[CO2]-grown plants showed that there was negative acclimation in the high-[CO2]-grown plants (9-16% reduction in g(s) when measured at 700 mu mol mol(-1)), but these were small compared to those for net CO2 assimilation rate (A, 21-36%). Stomatal acclimation was more clearly evident in the curve of stomatal response to intercellular [CO2] (c(i)) which showed a reduction in stomatal sensitivity at low c(i) in the high-[CO2]-grown plants. Stomatal density showed no change in response to growth in high growth [CO2] Long-term stomatal and photosynthetic acclimation to growth in high [CO2] did not markedly change the 2.5- to 3-fold increase in gas-exchange-derived wafer use efficiency caused by high [CO2].