Implications of Stomatal Interactions

Author

Thomas Norman Buckley, Utah State University

Date of Award:

5-1-1999

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Committee Chair(s)

Keith A. Mott

Committee

Keith A. Mott

Committee

James W. Haefner

Committee

Richard J. Mueller

Committee

Martyn M. Caldwell

Committee

Edmund D. Brodie

Abstract

Though stomatal apertures often vary randomly within a leaf, suggesting somata behave independently, recent evidence suggests stomata may interact. In the phenomenon of patchy stomatal conductance, stomatal behavior becomes coordinated at the intermediate scale of one or more areoles but discoordinated at larger scales. This has two general implications. First, it makes relationships between certain gas exchange properties highly scale dependent, affecting the interpretation of large-scale measurements in terms of small-scale properties and the upscaling of models based on small-scale mechanisms. Second, it indicates some yet-unidentified mechanism for stomatal interactions. A model of gas exchange in a leaf with heterogeneous stomatal conductance was developed to determine how qualitative features of conductance distributions influence the relationship measured by gas exchange between leaf CO₂ assimilation rate and intercellular CO₂ partial pressure. Simulations showed bimodal distributions, and those skewed toward or centered at low conductance values had large effects on this relationship, but most other distributions had little effect. These results resolve a discrepancy between Cheeseman's conclusion that patchy stomatal conductance cannot significantly change the assimilation/CO₂ relationship, and data documenting rapidly reversible changes in this curve concurrent with patchy stomatal conductance. This model was then extended to include leaf energy balance and used to determine the effects of stomatal heterogeneity on curvature in the relationship between assimilation and transpiration rates. Simulations showed this curvature is negative under most conditions but can become positive at low boundary layer conductance (more readily at high air temperatures and absorbed radiation). Mathematical analysis shows that multiple "optimal" patterns of stomatal behavior exist under positive curvature, extending the theory of stomatal optimization. To test the hypothesis that distant stomata in wheat (Triticum aestivum L.) leaves interact by a hydraulic mechanism, gas exchange was controlled and monitored independently in one region of a leaf while photon flux was perturbed elsewhere in the same leaf. Stomata in the unperturbed region responded to the distant perturbation in a manner consistent with hydraulic interactions. These long-distance interactions have implications for both measuring and scaling gas exchange properties.

Recommended Citation

Buckley, Thomas Norman, "Implications of Stomatal Interactions" (1999). Biology. 661.
https://digitalcommons.usu.edu/etd_biology/661