Differential coordination of stomatal conductance, mesophyll conductance, and leaf hydraulic conductance in response to changing light across species

Abstract

Stomatal conductance (gs) and mesophyll conductance (gm) represent major constraints to photosynthetic rate (A), and these traits are expected to coordinate with leaf hydraulic conductance (Kleaf) across species, under both steady-state and dynamic conditions. However, empirical information about their coordination is scarce. In this study, Kleaf, gas exchange, stomatal kinetics, and leaf anatomy in 10 species including ferns, gymnosperms, and angiosperms were investigated to elucidate the correlation of H2O and CO2 diffusion inside leaves under varying light conditions. Gas exchange, Kleaf, and anatomical traits varied widely across species. Under light-saturated conditions, the A, gs, gm, and Kleaf were strongly correlated across species. However, the response patterns of A, gs, gm, and Kleaf to varying light intensities were highly species dependent. Moreover, stomatal opening upon light exposure of dark-adapted leaves in the studied ferns and gymnosperms was generally faster than in the angiosperms; however, stomatal closing in light-adapted leaves after darkening was faster in angiosperms. The present results show that there is a large variability in the coordination of leaf hydraulic and gas exchange parameters across terrestrial plant species, as well as in their responses to changing light.