Conclusions
We have demonstrated that stomata may constitute a major pathway for FWU
when open. The measured water fluxes suggest that the main mechanism
underlying the transport of water across stomata is vapor diffusion
through the stomatal pore, with in-leaf distribution being a combination
of diffusion and liquid paths (same as across the cuticle). Further, we
propose that the interplay between cuticular conductance and the
capacity of the stomata to remain open can be a specific trait that
allows for opening stomata in response to surface hydration. The total
amount of water absorbed by FWU cannot sustain transpiration, but it can
provide a means of survival allowing for the recovery of plant
physiological functions after severe stress. Future research on leaf
surface dynamics, e.g. stomatal responses to water condensation and
temperature or cuticular changes as affected by temperature or degree of
hydration can contribute to better understand FWU mechanisms and
functional significance.