Boundary layer and stomatal control over leaf fluxes

The resistances encountered by molecules of carbon dioxide in moving into the leaf from the source in the ambient air to the sink at the sites of reaction in the chloroplasts may be used to describe quantitatively specific anatomical and physiological responses to environment . . . Similarly, the resistances to the transfer of water through the leaf from the source, which can be considered to be at the termination of the xylem, to the sink in the ambient air, first as a liquid and then as a vapour, describe adaptations and responses of the leaf to control water loss . . .Paul Jarvis (1971)