An unusual formation of tension wood in a natural forest Acacia sp.

Holzforschung ◽  
2004 ◽  
Vol 58 (3) ◽  
pp. 241-245 ◽  
Author(s):  
W.E. Hillis ◽  
R. Evans ◽  
R. Washusen
Keyword(s):  
Tension Wood ◽  
Microfibril Angle ◽  
Normal Wood ◽  
Microstructural Characteristics ◽  
Cellulose Crystallite ◽  
Grain Formation ◽  
Dark Colour ◽  
Similar Intensity ◽  
Unusual Formation

Abstract The determination of microfibril angle (MFA), cellulose crystallite width and microdensity by SilviScan-2 at CSIRO confirmed that several dark bands in the heartwood of an Acacia species were associated with tension wood (TW) fibres. The straight log was taken from a tree of about 30 years of age that had been apparently growing vertically as there were no signs of the usual stimuli for TW formation. The continuous dark bands of about 5 mm width extended radially from the inner heartwood in a spiral pattern and were separated by continuous normal wood bands of similar width. The TW bands continued in the sapwood from the heartwood boundary to the cambium but were not coloured. The dark colour of the TW was probably caused by extractives being polymerised at the heartwood boundary by enzymes in the TW fibres in the sapwood. The MFA and cellulose crystallite width indicated the TW in a band was of similar intensity throughout its length, indicating similar microstructural characteristics at different cambial ages. The initiation of spiral grain formation occurs before that of tension wood in the Acacia samples studied.

Relationships between Density, Shrinkage, Extractives Content and Microfibril Angle in Tension Wood from Three Provenances of 10-Year-Old Eucalyptus globulus Labill

Holzforschung ◽  
2001 ◽  
Vol 55 (2) ◽  
pp. 176-182 ◽  
Author(s):  
R. Washusen ◽  
P. Ades ◽  
R. Evans ◽  
J. Ilic ◽  
P. Vinden
Keyword(s):  
Wood Density ◽  
Eucalyptus Globulus ◽  
Tension Wood ◽  
Microfibril Angle ◽  
Positive Association ◽  
Normal Wood ◽  
X Ray Diffraction ◽  
X Ray ◽  
Saturation Method ◽  
Improvement Programs

Summary Density and microfibril angle (MFA) of tension wood and normal wood were assessed in the sapwood and heartwood, from three provenanaces of 10-year-old Eucalyptus globulus Labill. Density was measured using a modified saturation method that also enabled the calculation of the extractives lost during saturation. Microdensity and MFA were determined by SilviScan 2, a rapid X-ray densitometry and X-ray diffraction system developed at CSIRO. Significant differences were found in density and extractives between provenances and also density between the sapwood and adjacent heartwood from each provenance. This result may explain some of the drying differences between provenances found in an earlier study (Washusen and Ilic 2000). Sapwood samples with high percentages of tension wood fibres had high density and a significant positive correlation was found between microdensity and tension wood fibre percentage. MFA was found to be very low in normal wood in the sapwood, where most tension wood was found, so tension wood could not be identified by MFA. The positive association between tension wood and wood density suggests that caution should be taken when selecting trees for high wood density in tree improvement programs.

Microfibril Angle Distribution of Poplar Tension Wood

IAWA Journal ◽  
2012 ◽  
Vol 33 (4) ◽  
pp. 431-439 ◽  
Author(s):  
Silke Lautner ◽  
Cordt Zollfrank ◽  
Jörg Fromm
Keyword(s):  
Electron Microscopy ◽  
Tension Wood ◽  
Microfibril Angle ◽  
Cellulose Microfibrils ◽  
Normal Wood ◽  
Angle Distribution ◽  
Transmission Electron ◽  
Wood Fibres ◽  
Characteristic Features ◽  
Fibril Angle

Tension wood of poplar (Populus nigra) branches was studied by lightand electron microscopy. The characteristic features of tension wood such as wider growth rings, reduced vessel density and higher gross density were confirmed by our results. Based on a novel combination of transmission electron microscopy (TEM) imaging and image analysis, involving Fourier transformation, the orientation of cellulose microfibrils in the S2- and G-layer was determined. Within the G-layer microfibril angle (MFA) was parallel to the growth axis (0°). However, in the S2 it was 13° in tension wood fibres and 4° in normal wood fibres. With the exception of the relatively low fibril angle in the S2 of tension wood fibres (13°) the results are in good agreement with those of the literature.

A Study of Eucalyptus Grandis and Eucalyptus Globulus Branch wood Microstructure

IAWA Journal ◽  
2005 ◽  
Vol 26 (2) ◽  
pp. 203-210 ◽  
Author(s):  
Russell Washusen ◽  
Robert Evans ◽  
Simon Southerton
Keyword(s):  
Tension Wood ◽  
Microfibril Angle ◽  
Eucalyptus Grandis ◽  
Local Variation ◽  
Experimental Measurements ◽  
X Ray ◽  
Stem Wood ◽  
Opposite Wood ◽  
Cellulose Crystallite ◽  
Branch Wood

Experimental measurements of cellulose crystallite width and microfibril angle (MFA) by X-ray diffractometry on SilviScan-2 and by conventional microtechniques revealed that the branch wood of the two species exhibited very similar trends in cellulose crystallite width and MFA. Cellulose crystallite width was greater on the upper side of the branches. Tension wood, as defined by the occurrence of gelatinous fibres, was found where cellulose crystallite width was greater than 3.0 nm and 3.1 nm in Eucalyptus grandis and E. globulus respectively. In the tension wood zones, MFA was lower than in the rest of the samples and so could be used to differentiate tension wood. On the lower side of the branches MFA determined from X-ray diffractometry unexpectedly exceeded 40° and fibres were often buckled in both the tangential and radial directions in both species. This local variation in the direction of the fibre axes contributed only slightly to the magnitude of the MFA determined by SilviScan-2. Even given this misalignment, the additional evidence gained from pit angles and cracks in fibre walls suggested that the MFA was indeed around 40° in the lower radius of the branches. This MFA is considerably larger than would be expected for eucalypt stem wood and it is suggested that opposite wood in eucalypt branches may provide a complimentary structural role to that of the tension wood. Experimental measurements of crystallite width produced by SilviScan-2 may be used to accurately locate tension wood zones in both species.

scholarly journals Growth stresses and cellulose structural parameters in tension and normal wood from three tropical rainforest angiosperm species

BioResources ◽  
2007 ◽  
Vol 2 (2) ◽  
pp. 235-251 ◽  
Author(s):  
Julien Ruelle ◽  
Hiroyuki Yamamoto ◽  
Bernard Thibaut
Keyword(s):  
Crystallite Size ◽  
Tension Wood ◽  
Tropical Rainforest ◽  
Structural Parameters ◽  
Microfibril Angle ◽  
Diffraction Method ◽  
Normal Wood ◽  
Experimental Calibration ◽  
Growth Stresses ◽  
Main Layer

Few studies have been conducted about relation between cellulose para-meters and biomechanical properties of wood in tropical angiosperms species. For this purpose, on 13 trees from 3 species of French Guyana tropical rainforest in a clear active process of restoring verticality, i) growth strains were measured in situ in order to determine the occurrence of tension wood within samples and ii) cellulose structural parameters were estimated on all the samples using X-ray diffraction method. Crystallite size was estimated from the full-width at half-maximum of the Miller index (002) arc diffraction and angle T was measured following Cave’s method. Relationships between these parameters and growth stresses were good and the variations between normal and tension wood were significant, i.e. a lower angle T and a larger crystallite size in tension wood. In order to have a good estimation of the microfibril angle in the main layer of the secondary wall for each species, an experimental calibration was done between angle T and microfibril angle observed with scanning electron microscopy.

THE ASSOCIATION BETWEEN CELLULOSE CRYSTALLITE WIDTH AND TENSION WOOD OCCURRENCE IN EUCALYPTUS GLOBULUS

IAWA Journal ◽  
2001 ◽  
Vol 22 (3) ◽  
pp. 235-243 ◽  
Author(s):  
Russell Washusen ◽  
Robert Evans
Keyword(s):  
Eucalyptus Globulus ◽  
Tension Wood ◽  
Rapid Assessment ◽  
Solid Wood ◽  
Normal Wood ◽  
X Ray Diffraction ◽  
Cellulose Crystallite ◽  
Hardwood Species ◽  
Commercially Important ◽  
Diffraction Patterns

The association between cellulose crystallite width and the occurrence of tension wood was assessed for Eucalyptus globulus Labill., a commercially important plantation hardwood species. Crystallite width (uncorrected for instrumental broadening) was determined from X-ray diffraction patterns collected on SilviScan-2, an instrument developed for the rapid assessment of wood microstructure. Comparisons of crystallite widths were made using 66 samples of tension wood and normal wood selected randomly from one tree known to have abundant tension wood. Tension wood was found to have significantly wider crystallites than normal wood. The mean crystallite widths were 3.6 nm for tension wood and 3.2 nm for normal wood. The normal wood crystallite widths were consistent with those reported in previous studies, allowing for an experimental broadening equivalent to about 0.5 nm in this work. This study demonstrates that SilviScan-2 is useful for the detection of tension wood in solid wood samples such as increment cores.

The nature of reaction wood. IV. Variations in cell wall organization of tension wood fibres

1955 ◽  
Vol 3 (2) ◽  
pp. 177 ◽  
Author(s):  
AB Wardrop ◽  
HE Dadswell
Keyword(s):  
Cell Wall ◽  
Tension Wood ◽  
Secondary Wall ◽  
Degree Of Crystallinity ◽  
Tropical Species ◽  
Normal Wood ◽  
Reaction Wood ◽  
Gelatinous Layer ◽  
Wood Fibres ◽  
Cell Wall Organization

The cell wall organization, the cell wall texture, and the degree of lignification of tension wood fibres have been investigated in a wide variety of temperate and tropical species. Following earlier work describing the cell wall structure of tension wood fibres, two additional types of cell wall organization have been observed. In one of these, the inner thick "gelatinous" layer which is typical of tension wood fibres exists in addition to the normal three-layered structure of the secondary wall; in the other only the outer layer of the secondary wall and the thick gelatinous layer are present. In all the tension wood examined the micellar orientation in the inner gelatinous layer has been shown to be nearly axial and the cellulose of this layer found to be in a highly crystalline state. A general argument is presented as to the meaning of differences in the degree, of crystallinity of cellulose. The high degree of crystallinity of cellulose in tension wood as compared with normal wood is attributed to a greater degree of lateral order in the crystalline regions of tension wood, whereas the paracrystalline phase is similar in both cases. The degree of lignification in tension wood fibres has been shown to be extremely variable. However, where the degree of tension wood development is marked as revealed by the thickness of the gelatinous layer the lack of lignification is also most marked. Severity of tension wood formation and lack of lignification have also been correlated with the incidence of irreversible collapse in tension wood. Such collapse can occur even when no whole fibres are present, e.g. in thin cross sections. Microscopic examination of collapsed samples of tension wood has led to the conclusion that the appearance of collapse in specimens containing tendon wood can often be attributed in part to excessive shrinkage associated with the development of fissures between cells, although true collapse does also occur. Possible explanations of the irreversible shrinkage and collapse of tension wood fibres are advanced.

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