Convective Gas Flow in Plant Aeration and Graham's Law of Diffusion

Abstract

Experiments with porous ceramic membranes and leaves of Nymphaea alba L. are described which demonstrate that the counter diffusion of gaseous components of different molar mass governed by Graham’s law of diffusion (not to be confused with Graham’s law of effusion) has to be taken into account to understand the exchange processes of gases between leaves of aquatic and amphibic plants and the outer atmosphere. The experiments are carried out under conditions under which the ratio of the maximum pore size r of the ceramic material to the mean free path length λ. of the molecules in air has a value of the order of λ/r ≈ 1