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

Stomatal conductance (g_s ) and mesophyll conductance (g_m ) represent major constraints to photosynthetic rate (A), and these traits are expected to coordinate with leaf hydraulic conductance (K_leaf ) across species, under both steady-state and dynamic conditions. However, empirical information about their coordination is scarce. In this study, K_leaf , gas exchange, stomatal kinetics, and leaf anatomy in 10 species including ferns, gymnosperms, and angiosperms were investigated to elucidate the correlation of H₂ O and CO₂ diffusion inside leaves under varying light conditions. Gas exchange, K_leaf , and anatomical traits varied widely across species. Under light-saturated conditions, the A, g_s , g_m , and K_leaf were strongly correlated across species. However, the response patterns of A, g_s , g_m , and K_leaf 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.