tailieunhanh - Báo cáo khoa học: "Aeration of the root system in Alnus glutinosa L. Gaertn. P. Schröder"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài:"Aeration of the root system in Alnus glutinosa L. Gaertn. P. Schröder. | 310s Ann. Sci. For. 1989 46 suppl. 31 Os-314s Forest Tree Physiology et al. eds. Elsevier INRA Aeration of the root system in Alnus glutinosa L. Gaertn. R Schroder Bot. Inst. Univ. Cologne Gyrhofstr. 15 D-5000 Kõln 41 . Introduction and theoretical considerations When soils are wet or flooded during winter or spring many plants suffer from persistent anoxia of their rhizospheres. Oxygen diffusion from the atmosphere through the wet soil is insufficient to overcome this 02 deficiency because of the low solubility and the low diffusion velocity of 02 in the aqueous phase. Thus it is obvious that the only plants that can survive in temporarily flooded ecosystems are those that have developed the ability to tolerate or to avoid root anoxia for longer periods of time. As has been recently shown Grosse and Schroder 1984 1985 1986 the wetland alder Alnus glutinosa L. Gaertn. is able to improve o2-supply to its root system by gas transport from the aerial parts of its stem to the roots. The gas transport in A. glutinosa is assumed to be thermo-osmotic. Thermo-osmosis of gases is a physicochemical effect based on Knud-sen-diffusion Takaishi and Sensui 1963 found in several plants living in wet habitats Grosse and Schroder 1986 Schro der etal. 1986 Grosse and Mevi-Schutz 1987 . Thermo-osmosis might generally be described as any flow of matter between two compartments under the influence of a temperature gradient through a membrane with pores in the range of the mean free path lengths of the gas molecules considered Knudsen 1910 Denbigh and Raumann 1952 Takaishi and Sensui 1963 . The mean free path length is defined as the average distance the gas molecules cover between successive collisions. For air molecules moving statistically with speeds according to Maxwell s law the mean free path length is zm. Due to the laws of Knudsen-diffusion restricted diffusion gas flow is always directed towards the warmer compartment a rise in gas pressure results in this .