Symposium IV: Sensing and responding to water

Abs # 40004: Stomata and Humidity: A Calculated Response?

Presenter:	Mott, Keith A, kmott@biology.usu.edu
Authors	Mott, Keith A (A)   Peak, David  (B)   West, Jevin D (A)   Messinger, Susanna M (A)
Affiliations:	(A): Biology Department, Utah State University (B): Physics Department, Utah State University

Stomata close when transpiration rate is increased by a reduction in atmospheric humidity. Although there is no consensus on the mechanism for this response, the number of viable possibilities is limited, and most evidence supports the involvement of other cells in the leaf in addition to the guard cells. One interesting aspect of stomatal responses to transpiration rate is that stomatal conductance frequently becomes patchy when a leaf is subjected to a decrease in atmospheric humidity. This can occur even when environmental conditions are uniform. During patchy episodes, hundreds or thousands of stomata behave in a coordinated manner. We have shown that these coordinated stomatal movements can be at least partially explained by hydraulic interactions between neighboring stomata, which suggests that stomata may be viewed as a locally-connected network. Patchiness does not arise in all experiments, and in many cases, conductance patches are short-lived and give way to a homogeneous distribution of stomatal conductance as the leaf approaches the new steady state at the lower humidity. Sometimes, however, conductance patches persist for many hours and show complex spatial and temporal dynamics. These dynamics are indistinguishable from those of locally-connected networks that perform an emergent distributed computation, i.e., a computation that arises at the level of the entire network, but is based on solely local interactions among the individual units. We suggest that leaves may perform such a computation in the process of achieving a new steady-state conductance following a perturbation in environmental conditions.