Differences in leaf anatomy determines temperature response of leaf hydraulic and mesophyll CO2 conductance in phylogenetically related C4 and C3 grass species

Leaf hydraulic and mesophyll CO2 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 CO2, 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 CO2 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.

Automated summary

The temperature responses of leaf hydraulic and mesophyll CO2 conductance differ between C4 and C3 species, indicating distinct effects on water movement and carbon uptake in relation to increasing leaf temperature.