Brändström, Jonas
- Department of Forest Products, Swedish University of Agricultural Sciences
Abstract
The ultrastructural organization of the outer layer of the secondary wall (i.e. S-1 layer) of Norway spruce (Picea abies (L.) Karst.) compression wood tracheids was investigated with emphasis on the microfibril angle. Light microscopy was used to study the orientation of soft rot cavities (viz. microfibril angle) in compression wood tracheids from macerated soft rot degraded wood blocks. In addition, surface and fracture characteristics of compression wood tracheids selected from a thermomechanical pulp were investigated using scanning electron microscopy (SEM). Results showed that the orientation of soft rot cavities varied little between tracheids and the angles were also consistent along the length of individual tracheids. The average S I microfibril angle in two selected annual rings was 90.0degrees +/- 2.7degrees and 88.9degrees +/- 2.4degrees respectively. SEM observations of the compression wood tracheids from the pulp showed distinct fractures between S-1 and S-2 or within S-1 and these fractures were oriented perpendicular to the tracheid axis. It was concluded that the microfibril angle of the S-1 layer of compression wood tracheids is higher and less variable than normal wood tracheids. This is considered an adaptation for restraining the compressive forces that act on leaning conifer stems or branches.
Keywords
compression wood; microfibril angle; outer layer; Picea abies; reaction wood; S-1; soft rot; thermomechanical pulp
Published in
IAWA Journal
2004, volume: 25, number: 4, pages: 415-423
Publisher: INT ASSOC WOOD ANATOMISTS
SLU Authors
UKÄ Subject classification
Forest Science
Permanent link to this page (URI)
https://res.slu.se/id/publ/3325