Abstract
Mesophyll conductance to CO(2) (g(m)) act as a significant limiting factor influencing the CO(2) assimilation rate (A(N)) during photosynthetic induction. However, the effect of vapor pressure deficit (VPD) on g(m) kinetics during light induction is not well clarified. We combined gas exchange with chlorophyll fluorescence measurements to assess the induction kinetics of g(m) during light induction under contrasting vapor pressure deficit (VPD) in two tree species with different stomatal conductance (g(s)) behavior, Catalpa fargesii and Pterocarya stenoptera. Our results revealed three key findings: (1) the coordination of g(m) and g(s) kinetics during light induction occurred in C. fargesii but not in P. stenoptera, and the model of g(s) kinetics largely determines whether the coordination of g(s) and g(m) exist in a given species; (2) a high VPD induced simultaneous changes in g(s) and g(m) kinetics in C. fargesii but had separated effects on g(s) and g(m) kinetics in P. stenoptera, indicating that the response of g(m) kinetics during light induction to VPD differs between species; and (3) the relative contribution of photorespiration to total electron flow was flexible in response to the change in relative diffusional and biochemical limitations, pointing out that photorespiration has a significant role in the regulation of photosynthetic electron flow during light induction. These results provide new sight into the species-dependent kinetics of g(m) and photorespiration during light induction.