The balance between RuBP carboxylation and RuBP regeneration: A mechanism underlying the interspecific variation in acclimation of photosynthesis to seasonal change in temperature

The ratio of the capacities of ribulose-1,5-bisphosphate (RuBP) regeneration to RuBP carboxylation (J_max/V_cmax) (measured at a common temperature) increases in some species when they are grown at lower temperatures, but does not increase in other species. To investigate the mechanism of interspecific difference in the response of J_max/V _cmax to growth temperature, we analysed the temperature dependence of V_cmax and J_max in Polygonum cuspidatum and Fagus crenata with the Arrhenius function. P. cuspidatum had a higher ratio of J _max/V_cmax in spring and autumn than in summer, while F. crenata did not show such change. The two species had a similar activation energy for V_cmax (E_aV) across seasons, but P. cuspidatum had a higher activation energy for J_max (E_aJ) than F. crenata. Reconstruction of the temperature response curve of photosynthesis showed that plants with an inherently higher E_aJ/E_aV (P. cuspidatum) had photosynthetic rates that were limited by RuBP regeneration at low temperatures and limited by RuBP carboxylation at high temperatures, while plants with an inherently lower E_aJ/E_aV (F. crenata) had photosynthetic rates that were limited solely by RuBP carboxylation over the range of temperatures. These results indicate that the increase in J _max/V_cmax at low growth temperatures relieved the limitation of RuBP regeneration on the photosynthetic rate in P. cuspidatum, but that such change in J_max/V_cmax would not improve the photosynthetic rate in F. crenata. We suggest that whether or not the J _max/V_cmax ratio changes with growth temperature is attributable to interspecific differences in E_aJ/E_aV between species.