© 1990 Heron Publishing—Victoria, Canada
Localization of the porous partition responsible for pressurized gas transport in Alnus glutinosa (L.) Gaertn.
H. B. Buchel and W. Grosse
Botanical Institute, University of Cologne, Gyrhofstraße 15, D-5000 Köln 41, FRG / Received December 18, 1989
Summary
The pressurized gas transport which improves the oxygen supply of the roots of the wetland tree black alder (Alnus glutinosa (L.) Gaertn.), is based on the existence of a thermo-osmotically active porous tissue partition in the lower part of the
trunk with pore diameters in the range of, or smaller than, the mean free path length of the gas molecules (e.g., 70 nm for
O2 at 20 °C and 100 kPa). Anatomical studies have shown that only the cambial layer or the phellogen of the lenticels have intercellular
spaces small enough to be responsible for thermo-osmotic activity. The final localization of the thermo-osmotically active
partition and the determination of the pore sizes were done by diffusion and effusion experiments with basal trunk pieces
of 3- to 4-year-old trees. The mean pore sizes of the intercellular system were not smaller than 100 nm in diameter in the
cambial layer separating the bark from the wood, but 14 ± 7 nm in diameter in the phellogen underlying the lenticels. Because
of these small pores, the phellogen of the lenticels is the significant thermo-osmotically active partition for the transport
of air to the root system in black alder.
