, Volume 97, Issue 4, pp 325–336

The relative role of stomata in transpiration and assimilation

  • I. R. Cowan
  • J. H. Troughton

DOI: 10.1007/BF00390212

Cite this article as:
Cowan, I.R. & Troughton, J.H. Planta (1971) 97: 325. doi:10.1007/BF00390212


The ways in which transpiration and assimilation depend on stomatal aperture are compared. It is shown that transpiration and assimilation are equally sensitive to change of stomatal aperture when the internal resistance to assimilation is equal to an effective resistance to evaporation which exists because of the coupling of heat and vapour exchanges between leaf and atmosphere. Generally the ratio of transpiration to assimilation changes with stomatal aperture in a manner which is determined by the relative magnitude of these resistances and on temperature. Some possible implications in relation to the optimal behaviour of stomata are discussed.

Copyright information

© Springer-Verlag 1971

Authors and Affiliations

  • I. R. Cowan
    • 1
  • J. H. Troughton
    • 1
  1. 1.Department of Environmental Biology, Research School of Biological SciencesAustralian National UniversityCanberra City
  2. 2.Physics and Engineering LaboratoryDepartment of Scientific and Industrial ResearchLower HuttNew Zealand

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