Calibration of a porometer in terms of diffusive resistance

✍ Scribed by Paul E. Waggoner

• Book ID: 102979663
• Publisher: Elsevier Science
• Year: 1965
• Weight: 648 KB
• Volume: 2
• Category: Article
• ISSN: 0002-1571
• DOI: 10.1016/0002-1571(65)90025-7

✦ Synopsis

The rate of pressure drop in a convenient leaf, porometer is shown to be a simple function of several separable components of flow resistance. Those due to stomata are arrived at by measuring or estimating the others. Stomatal resistance is also calculated from viscous flow theory and the observed dimensions of sample stomata or their replicas. Measured and calculated values for barley agree moderately well, thus justifying the model used in calculation.

With standard molecular diffusion theory, the same dimensions give the diffusive resistance of the stomata, which is the quantity of interest in transpiration or assimilation studies. With suitable averaging procedures to relate the properties of single pores to those of whole leaves, a simplified theoretical relation between viscous and diffusive resistance is found permitting conversion of porometer readings directly into diffusive resistances.