Interspecific variation in the temperature response of mesophyll conductance is related to leaf anatomy.

Although mesophyll conductance (g m ) is known to be sensitive to temperature (T), the mechanisms underlying the temperature response of g m are not fully understood. In particular, it has yet to be established whether interspecific variation in g m -T relationships is associated with mesophyll anatomy and vein traits. In the present study, we measured the short-term response of g m in eight crop species, and leaf water potential (Ψ leaf ) in five crop species over a temperature range of 15-35°C. The considered structural parameters are surface areas of mesophyll cells and chloroplasts facing intercellular airspaces per unit leaf area (S m and S c ), cell wall thickness (T cw ), and vein length per area (VLA). We detected large interspecific variations in the temperature responses of g m and Ψ leaf . The activation energy for g m (E a,gm ) was found to be positively correlated with S c , although it showed no correlation with T cw . In contrast, VLA was positively correlated with the slope of the linear model of Ψ leaf -T (a), whereas E a,gm was marginally correlated with VLA and a. A two-component model was subsequently used to model g m -T relationships, and the mechanisms underlying the temperature response of g m are discussed. The data presented here indicate that leaf anatomy is a major determinant of the interspecific variation in g m -T relationships.