CONVECTIVE GAS-FLOW IN PLANT AERATION AND GRAHAMS LAW OF DIFFUSION

Experiments with porous ceramic membranes and leaves of Nymphaea alba L. are described which demonstrate that the counter diffusion of gaseo us components of different molar mass governed by Graham's law of diff usion (not to be confused with Graham's law of effusion) has to be tak en into account to understand the exchange processes of gases between leaves of aquatic and amphibic plants and the outer atmosphere. The ex periments are carried out under conditions under which the ratio of th e maximum pore size r of the ceramic material to the mean free path le ngth lambda of the molecules in air has a value of the order of lambda /r approximate to 1.