scholarly journals Evidence that release of internal stress contributes to drying strains of wood

Holzforschung ◽  
2012 ◽  
Vol 66 (3) ◽  
Author(s):  
Bruno Clair
Keyword(s):  
Tension Wood ◽  
Drying Shrinkage ◽  
Cellulose Microfibrils ◽  
Internal Stresses ◽  
Schematic Model ◽  
Normal Wood ◽  
Longitudinal Shrinkage ◽  
Fibre Direction ◽  
Desorption Process ◽  
Chestnut Wood

Abstract Wood shrinks during drying, with the departure of bond water. Along the fibre direction, the magnitude of this shrinkage is mainly governed by the orientation of cellulose microfibrils (MF) in the cell wall. However, tension wood has an unexpectedly high longitudinal shrinkage considering the fact that MFs are oriented nearly parallel to the cell direction. This effect is thought to be caused by the gel collapse of the G-layer; however, some species producing a tension wood without a G-layer also exhibit a higher longitudinal shrinkage than normal wood. The aim of this study is to analyse the contribution of maturation stresses to drying shrinkage. Longitudinal and tangential drying shrinkage of tension wood and normal wood were measured on two sets of matched chestnut wood samples. The first set was directly oven-dried, whereas on the second set, a hygrothermal treatment released the maturation stress before oven-drying. The analysis of the strains during each step of the procedure revealed that part of the drying shrinkage is caused by the release of internal stresses during the desorption process. Finally, a tentative schematic model is proposed, taking into account the cumulative contributions to longitudinal drying shrinkage.

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.

scholarly journals SHRINKAGE OF THE GELATINOUS LAYER OF POPLAR AND BEECH TENSION WOOD

IAWA Journal ◽  
2001 ◽  
Vol 22 (2) ◽  
pp. 121-131 ◽  
Author(s):  
Bruno Clair ◽  
Bernard Thibaut
Keyword(s):  
Cell Wall ◽  
Tension Wood ◽  
Normal Wood ◽  
Longitudinal Shrinkage ◽  
Sem Observation ◽  
Gelatinous Layer ◽  
Dry Conditions

Macroscopic longitudinal shrinkage of beech and poplar tension wood is higher than in normal wood. This shrinkage is the result of mechanical interactions of cell wall layers. SEM observation of cut, dried surfaces showed that longitudinal shrinkage is much greater in the gelatinous layer than in other layers. AFM topographic images of the same cells, both in water and in air-dry conditions, confirm this result. Measurements on sections indicate around 4.7% longitudinal shrinkage for the G layer.

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.

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.

scholarly journals The Nature of Reaction Wood

1948 ◽  
Vol 1 (1) ◽  
pp. 3 ◽  
Author(s):  
AB Wardrop ◽  
HE Dads Well
Keyword(s):  
Tensile Strength ◽  
Tension Wood ◽  
Reaction Wood ◽  
Fibre Structure ◽  
Longitudinal Shrinkage ◽  
High Tensile Strength ◽  
Wood Fibres

The structure of tension wood fibres is ofconsiderahle academic and practicalinterest, both in relation to considerations of the stimuli which produce them,and to studies of the influence of fibre structure on the properties of the wood asa whole. As is well known, the chief abnormal properties of tension wood lie inits unusually high longitudinal shrinkage, its high tensile strength, and its lowcompressive strength .

Wood quality in artificially inclined 1-year-old trees of Eucalyptus regnans — differences in tension wood and opposite wood properties

2011 ◽  
Vol 41 (5) ◽  
pp. 930-937 ◽  
Author(s):  
Shakti S. Chauhan ◽  
John C.F. Walker
Keyword(s):  
Tension Wood ◽  
Wood Quality ◽  
Basic Density ◽  
Wood Properties ◽  
Acoustic Velocity ◽  
Volumetric Shrinkage ◽  
Longitudinal Shrinkage ◽  
Eucalyptus Regnans ◽  
New Approach ◽  
Opposite Wood

This paper presents a new approach to assess wood quality in 1-year-old Eucalyptus regnans F. Muell. Twenty-two seedlings were grown tilted to induce tension wood and acoustic velocity, basic density, longitudinal shrinkage, and volumetric shrinkage of both opposite wood and tension wood were assessed subsequently. Longitudinal growth strains were also estimated in the leaning stems by sawing along the length through the pith and measuring the bending of the two halves. The derived longitudinal growth strain, which varied from 708 to 2319 µε, was uncorrelated with stem and wood characteristics. Wood characteristics differed significantly between upper-side wood (predominantly tension wood) and lower-side wood (opposite wood). Tension wood was characterized by a higher acoustic velocity (high stiffness), basic density, and volumetric shrinkage compared with opposite wood. Tension wood also exhibited significant collapse and dimensional distortion such as twisting. Longitudinal shrinkage exhibited a significant negative relationship with acoustic velocity in opposite wood and a positive relationship with the basic density in tension wood. This new approach has potential in early selection of breeding material with superior normal wood properties from 1-year-old material by isolating the influence of tension wood. This approach can also be useful in understanding the variability in propensity of tension wood production in breeding populations.

Hygrothermal recovery of compression wood in relation to DMSO swelling and drying shrinkage

Holzforschung ◽  
2020 ◽  
Vol 74 (8) ◽  
pp. 789-797
Author(s):  
Shuoye Chen ◽  
Miyuki Matsuo-Ueda ◽  
Masato Yoshida ◽  
Hiroyuki Yamamoto
Keyword(s):  
Compression Wood ◽  
Wood Specimen ◽  
Microfibril Angle ◽  
Drying Shrinkage ◽  
Growth Stress ◽  
Normal Wood ◽  
Dimensional Changes ◽  
The Matrix ◽  
Dmso Treatment ◽  
Hygrothermal Treatment

AbstractTo understand the irreversible dimensional changes caused by hygrothermal treatment of green wood, i.e. hygrothermal recovery (HTR), green hinoki compression wood (CW) and normal wood (NW) were hygrothermally (HT) treated in water at 100°C for 120 min and their HTR strains were determined. The specimens were then swollen using dimethyl sulfoxide (DMSO) and then completely dried after solvent exchange with water at room temperature. Their HTR strains were then compared with their DMSO swelling and drying shrinkage strains. The volumetric HTR strains in the CW were about twice as large as those in the NW. Moreover, the microfibril angle (MFA) was found to be an important factor for controlling the HTR intensity. A clear commonality between the HTR behavior and both DMSO swelling and drying shrinkage behavior was identified, which indicates that HTR is caused by volumetric changes in the matrix substances. HTR has been defined as a phenomenon due to the release of locked-in growth stress when a wood specimen is HT treated. To determine whether DMSO treatment has a similar effect as hygrothermal treatment, both HT-untreated and HT-treated specimens were swollen using DMSO, and their dimensional changes during and after DMSO treatment were compared. The results showed that DMSO treatment is a possible alternative for releasing the locked-in growth stress.

scholarly journals Diversity of anatomical structure of tension wood among 242 tropical tree species

IAWA Journal ◽  
2019 ◽  
Vol 40 (4) ◽  
pp. 765-784 ◽  
Author(s):  
Barbara Ghislain ◽  
Julien Engel ◽  
Bruno Clair
Keyword(s):  
Wood Density ◽  
Tree Species ◽  
Tension Wood ◽  
Wood Anatomy ◽  
Tropical Tree ◽  
Blue Staining ◽  
Common Mechanism ◽  
Vertical Position ◽  
Normal Wood ◽  
Tropical Tree Species

ABSTRACT Angiosperm trees produce tension wood to actively control their vertical position. Tension wood has often been characterised by the presence of an unlignified inner fibre wall layer called the G-layer. Using this definition, previous reports indicate that only one-third of all tree species have tension wood with G-layers. Here we aim to (i) describe the large diversity of tension wood anatomy in tropical tree species, taking advantage of the recent understanding of tension wood anatomy and (ii) explore any link between this diversity and other ecological traits of the species. We sampled tension wood and normal wood in 432 trees from 242 species in French Guiana. The samples were observed using safranin and astra blue staining combined with optical microscopy. Species were assigned to four anatomical groups depending on the presence/absence of G-layers, and their degree of lignification. The groups were analysed for functional traits including wood density and light preferences. Eighty-six% of the species had G-layers in their tension wood which was lignified in most species, with various patterns of lignification. Only a few species did not have G-layers. We found significantly more species with lignified G-layers among shade-tolerant and shade-demanding species as well as species with a high wood density. Our results bring up-to-date the incidence of species with/without G-layers in the tropical lowland forest where lignified G-layers are the most common anatomy of tension wood. Species without G-layers may share a common mechanism with the bark motor taking over the wood motor. We discuss the functional role of lignin in the G-layer.

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