Importance to Gas Exchange of Mass Flow of Air through Leaves.

A reanalysis of results from a recent paper on the effect of oscillation on gas exchange through leaves of cottonwood (Populus deltoides, Marsh) is presented. Mass flow of air through the leaf cannot account for the observed increase in gas exchange during oscillation in that experiment. Consideration of various published data shows that in the field, mass flow will not constitute more than a few per cent of the total exchange for most agricultural crops, but may be a significant part of the exchange for the leaves of tall trees, as they can be exposed to high winds.