Bacteria in radial shakes in pedunculate oak trees | Bakterien in Radialrissen von Stiel-Eiche
2001
Schmidt, Olaf | Moreth, Ute | Butin, Heinz | Kehr, Rolf
The occurrence and distribution of bacteria in so-called ‘frost cracks’ in oak trees were investigated to determine the possible role of bacteria in the formation and development of radial cracks in living trees. The bacterial samples were taken from wood cross-sections obtained at different trunk heights from freshly felled oak trees showing signs of ‘frost cracks’. Inner portions of the cracks often yielded bacteria, the colonization density of which declined from the surface of the crack to the adjacent deeper wood tissues. Controls from sound wood not affected by cracks were sterile in general. The number of bacteria declined from the pith to the sapwood boundary. The sapwood was sterile for the most part. Bacteria colonization was more extensive in cross-sections from the lower parts of the tree than in cross-sections taken at heights of 1.5 or 2 meters. The pure cultures belonged mainly to Bacillaceae and to other microaerophilic or facultatively anaerobic bacteria, presumably lactic acid bacteria and Enterobacteriaceae. Degradation tests on woody cell walls and their components under aerobic and anaerobic conditions revealed a pattern typical for ‘wood bacteria’, i. e. degradation of parenchyma cells, pectin and cellulose derivatives as well as the lack of activity in respect to crystalline cellulose and woody cell walls. Rarely, other organisms such as a few Deuteromycetes and Ascomycetes were present in the cracks. The laboratory results may support the assumption that bacteria could be involved in the deterioration of the wood structure, especially of pectins and cellulose derivatives, and may contribute to the formation and further development of radial cracks in the wood of living trees.
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