Oxygen Supply of Roots by Gas Transport in Alder-Trees

It is generally accepted that oxygen diffuses according to the gradient of its partial pressure from the surface of the plants into the heterotrophic tissues through the intercellular spaces. The present experiments show evidence of an additional manifold higher oxygen supply due to a gas transport in leaved as well as leafless trees of Alnus glutinosa (L.) Gaertner. This gas transport is directed from the stems to the roots. It is driven by a thermo-osmotic pressurisation within the air space system of the stems, resulting from temperature gradients up to 3.6 K between the stem and the ambient air following the absorption of light energy by the brownish pigments of the bark. This gas phase phenomena appears to enable the alder-trees to survive and grow in wet soil resulting from a high water table or in waterlogged soil.