Differences in leaf anatomy determines temperature response of leaf hydraulic and mesophyll CO 2 conductance in phylogenetically related C 4 and C 3 grass species

Summary Leaf hydraulic and mesophyll CO 2 conductance are both influenced by leaf anatomical traits, however it is poorly understood how the temperature response of these conductances differs between C 4 and C 3 species with distinct leaf anatomy. This study investigated the temperature response of leaf hydraulic conductance ( K leaf ), stomatal ( g s ) and mesophyll ( g m ) conductance to CO 2 , and leaf anatomical traits in phylogenetically related Panicum antidotale (C 4 ) and P. bisulcatum (C 3 ) grasses. The C 4 species had lower hydraulic conductance outside xylem ( K ox ) and K leaf compared with the C 3 species. However, the C 4 species had higher g m compared with the C 3 species. Traits associated with leaf water movement, K leaf and K ox , increased with temperature more in the C 3 than in the C 4 species, whereas traits related to carbon uptake, A net and g m , increased more with temperature in the C 4 than the C 3 species. Our findings demonstrate that, in addition to a CO 2 concentrating mechanism, outside‐xylem leaf anatomy in the C 4 species P . antidotale favours lower water movement through the leaf and stomata that provides an additional advantage for greater leaf carbon uptake relative to water loss with increasing leaf temperature than in the C 3 species P. bisulcatum .