An Examination of the Leaf Quaking Adaptation and Stomatal Distribution in Populus tremuloides Michx.

The leaves of quaking aspen (Populus tremuloides Michx.) have a flattened petiole that allows them to quake (oscillate and roll) under low wind velocities. It was hypothesized that this adaptation might enable the plant to respond to windy conditions that would increase transpirational losses. No effects of wind with or without leaf quaking on stomatal resistance were observed under controlled conditions in the field. If wind and leaf quaking affect stomatal resistance, such effects must be small in comparison to those caused by other factors such as leaf water potential and ambient humidity.Aspen leaves are hypostomatal with stomata evenly distributed over the abaxial surface. This observation casts serious doubt on the hypothesis that quaking is an adaptation to increase bulk air flow through amphistomatal leaves.