Elevated CO2 concentrations may enh

Elevated CO2 concentrations may enhance potential net photosynthesis of C3 plants because ribulose-1,5-bisphophate car- boxylase/oxygenase (rubisco), an enzyme involved in both CO2 fixation and photorespiration, is not CO2 saturated at the current concentration (Drake et al., 1997). Thus, an increase in ambient CO2 raises the leaf internal CO2 concentration and the CO2/O2 ratio at the rubisco site, favoring carboxylation over oxygenation in ribulose-1,5-bisphosphate (RuBP). Therefore, elevated CO2 con- centrations can reduce photorespiration and thus cellular H2O2 production associated with glycolate metabolism (Pritchard et al.,