acclimation to CO2; Fagus sylvatica; maximum carboxylation rate; Rubisco activity and amount; photosynthesis

In this study, we estimated the major photosynthetic responses of European beech (Fagus sylvatica L.) seedlings to the impact of elevated carbon dioxide concentration ([CO2]). We compared diurnal changes in Rubisco (ribulose-1,5-bisphosphate carboxylase/ oxygenase) enzyme activity observed in vivo and in vitro and also amount of this enzyme. Rubisco catalyses carboxylation of ribulose-1,5-bisphosphate (RuBP), the first step of photosynthetic carbon assimilation, in competition with oxygenation of RuBP that leads to the photorespiratory pathway. Our analysis shows that the short-term exposure to elevated [CO2] doesnot change the maximum carboxylation rate of Rubisco in vivo. In contrary, we found lower total activity in vitro; however, the amount of Rubisco was higher in trees cultivated under elevated as compared to ambient [CO2]. Treatment in elevated [CO2] thus led to the decrease of total Rubisco activity per unit amount pointing to that higher portion of Rubisco remains inactive.

In this study, we estimated the major photosynthetic responses of European beech (Fagus sylvatica L.) seedlings to the impact of elevated carbon dioxide concentration ([CO2]). We compared diurnal changes in Rubisco (ribulose-1,5-bisphosphate carboxylase/ oxygenase) enzyme activity observed in vivo and in vitro and also amount of this enzyme. Rubisco catalyses carboxylation of ribulose-1,5-bisphosphate (RuBP), the first step of photosynthetic carbon assimilation, in competition with oxygenation of RuBP that leads to the photorespiratory pathway. Our analysis shows that the short-term exposure to elevated [CO2] doesnot change the maximum carboxylation rate of Rubisco in vivo. In contrary, we found lower total activity in vitro; however, the amount of Rubisco was higher in trees cultivated under elevated as compared to ambient [CO2]. Treatment in elevated [CO2] thus led to the decrease of total Rubisco activity per unit amount pointing to that higher portion of Rubisco remains inactive.