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 (psi(leaf)) in five crop species over a temperature range of 15-35 degrees 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 psi(leaf). The activation energy for g(m) (E-a,E-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 psi(leaf)-T (a), whereas E-a,E-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.

Automated summary

This study measured the short-term response of mesophyll conductance (g(m)) and leaf water potential (psi(leaf)) in different crop species at various temperatures. The results showed significant interspecific variations in g(m) and psi(leaf) temperature responses. Leaf anatomy was found to be the major determinant of interspecific variation in g(m) temperature relationships.