A Pressure-Infiltration Method for Estimating Stomatal Dimensions


A Pressure-Infiltration Method for Estimating Stomatal opening in Conifers

Fry K. E., Walker R. B. (1967)

in Ecology Volume 48, Issue 1: 155–157 – DOI: 10.2307/1933428 –



A method is presented for estimating large and small changes of stomatal aperture in conifer needles by means of partial infiltration of alcoholic fluids under pressure.

Needles are placed in a small, widowed chamber and are observed while the pressure is increased. Minute reflections of light which emanate from the stomata indicate the specific pressure at which infiltration begins.

In theory this characteristic infiltration pressure is primarily a function of the stomatal pore size. In excised needles of Douglas fir (Pseudotsuga menziesii) infiltration pressures were highly correlated with transpiration rates.

A basic formula is given for estimating stomatal widths from the infiltration pressure.


Published by

Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.

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