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Journal ArticleDOI

Shrinkage of the gelatinous layer of poplar and beech tension wood

01 Jan 2001-Iawa Journal (Brill)-Vol. 22, Iss: 2, pp 121-131

AbstractMacroscopic 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.

Topics: Shrinkage (66%)

Summary (1 min read)

Longitudinal shrinkage in wood

  • Like all other wood properties, hygroexpantion presents a very important anisotropy.
  • The knowledge of the wood cell structure, as a multi-layer fibre composite, allows the modelling of the longitudinal shrinkage.
  • A high local level of growth stress is always related to presence of tension wood (Trénard & Guéneau 1975; Sassus 1994).
  • Finally a last superficial planning is done manually with a brand new razor blade in order to produce a nice transverse surface, the sample being always kept in moist condition.

Scanning electron microscopy

  • Both in poplar and beech, one cell is observed with two angle of view, at first perpendicular to the surface and then tilted 70° from that direction (Fig. 8).
  • The x coordinate is given directly by the first image while the y coordinate can be calculated with equation 1 using both images (Fig. 7).
  • These topographic profiles allow measurements of differential shrinkage between cell wall layers.
  • Thin sections Several poplar cells were observed after drying.
  • Mean measurements of differential restraint between G layer and compound middle lamella (CML) are 1.99 µm for a face, 1.83 µm for the other and 3.82 µm for the sum of faces.

Atomic force microscopy

  • The profile in water (Fig. 11 A') shows that there is already a small retract of Glayer before drying.
  • The profile in water after 2 hours in 80°C water (Fig. 11 B') shows very few additional retract of G-layer before drying.
  • The profile in air-dry conditions (Fig. 11 C') confirms the presence of a more important shrinkage in G-layer than in other layers.
  • After the blade moving, due to recovery of these different stress states, softer and thinner layers lay above stiffer ones like the G-layer.
  • Again, it can be argued that this separation allows a more complete release of growth stress in the G-layer, so that, this further differential shrinkage is another expression of growth stress only.

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Shrinkage of the Gelatinous Layer of Poplar and Beech
Tension Wood
Bruno Clair, Bernard Thibaut
To cite this version:
Bruno Clair, Bernard Thibaut. Shrinkage of the Gelatinous Layer of Poplar and Beech Tension Wood.
IAWA Journal, Brill publishers, 2001, 22, pp.121-131. �10.1163/22941932-90000273�. �hal-00004542�

SHRINKAGE OF THE GELATINOUS LAYER OF
POPLAR AND BEECH TENSION WOOD
by
Bruno Clair & Bernard Thibaut
LMGC – Bois, Université Montpellier II, CC 081, Place E. Bataillon,
34095 Montpellier, France (e-mail: clair@lmgc.univ-montp2.fr).
Published in IAWA Journal, Vol. 22 (2), 2001: 121–131
SUMMARY
Macroscopic longitudinal shrinkage in beech or poplar tension wood
is higher than in normal wood. This shrinkage is the result of cell
walls layers mechanical interactions. In order to complete the basic
data with a view to modelling the cell wall, we are interested in
shrinkage differences between cell wall layers and especially of G-
layer in poplar and beech. Wood samples in green condition are cut
with a razor blade, and then dried before observation. SEM
observation shows longitudinal shrinkage much more important in
gelatinous layer than in other layers. AFM topographic images of
same cells, both in water and in air-dry conditions, confirm this result.
Measurements on thin sections allow quantitative results around 4.7 %
longitudinal shrinkage for G-layer.
Key words: cell wall, gelatinous layer, shrinkage, tension wood.
INTRODUCTION
Longitudinal shrinkage in wood
Like all other wood properties, hygroexpantion presents a very important
anisotropy. Between green condition and ovendry condition, shrinkage ranges from
0.05 % to 0.3 % in longitudinal direction, 3 % to 6 % in radial direction and from
6 % to 12 % in tangential one (Skaar 1988). According to these values, the
hygroexpension in axial direction is not apparently a problem for the user. However,
two cases exist when longitudinal shrinkage starts to be more important: in reaction
wood (tension wood of angiosperms and compression wood of gymnosperms) and
juvenile wood (Skaar 1988). In these two types of wood, axial shrinkage can reach
1 % or more (Nepveu 1994). For these woods, shrinkage value cannot be considered
as negligible, because wood beams have generally their longer distances in axial
direction. These important differences can be explained by the wood fibre structure.

2 IAWA Journal,
From wood fibre structure to shrinkage modelling
The knowledge of the wood cell structure, as a multi-layer fibre composite, allows
the modelling of the longitudinal shrinkage.
One of the first models, which is still a reference, is the Barber and Meylan 's
one (1964) refined by Barber (1968). This model considers that the cell wall is
reduced to S
2
layer. S
2
layer is described like an amorphous hygroscopic matrix in
which are imbedded parallel crystalline microfibrils which act to restrain
hygroexpention in the direction parallel to their axes (Fig. 1) (Cave 1972a). Thus,
microfibril angle is the determinant factor of longitudinal shrinkage. Low angle of
microfibril in relation to axial direction induces low axial shrinkage (like in normal
wood) and high angle allows a higher shrinkage (like in juvenile or compression
wood). Later, other models integrating other components properties (cellulose,
hemicellulose and lignin), changes in matrix behaviour during drying and
introducing the different cell wall layers have been proposed to refine this first
theory (Barrett et al. 1972; Cave 1972b, 1978; Sassus 1998; Gril et al. 1999;
Yamamoto 1999).
Matrix Microfibrils Woody mater
Fig. 1: schematic representation of the "reinforced matrix" (Sassus 1998)
These models give a good understanding of macroscopic axial shrinkage for
different values of microfibril angle, for normal, compression and juvenile wood.
However, they cannot explain the behaviour of tension wood with gelatinous
layer. In fact, in G layer, microfibril angle is very low or nil (Chaffey 2000), even
when macroscopic longitudinal shrinkage is high (Clarke 1937; Chow 1946; Sassus
1998). Norberg and Meier (1966) had isolated portion of G layer and said that they
do not show high longitudinal shrinkage. The G layer is generally loosened from S
2
layer and this latter one is very thin in tension wood. So these authors and Boyd
(1977) assume that in that case, longitudinal shrinkage is produced by S
1
layer, G
layer being unable to prevent it.
MATERIAL AND METHODS
One poplar (Populus cv I4551) and one beech (Fagus sylvatica L.), were chosen for
this study. These species are known to have characteristic tension wood with G layer
and a high macroscopic axial shrinkage.
Populus cv I4551
During the growing period, a young one year old poplar tree in a container is tilted
35° from the vertical. At the end of that period, the stem has nearly regained its
verticality by producing tension wood on the upper side (Fig. 2). Wood sample
taken from this tension wood zone have characteristic anatomical features
presenting a large amount of fibre with G layer and very thin S
2
layer (Fig. 4 A).

Clair G layer shrinkage 3
35°
Fig. 2: Recovery of the verticality of a poplar stem after the container have been
tilted 35°. Tension wood is produced on the upper side.
Fagus Sylvatica (L.)
A 150 years old tree was chosen after measurement of peripheral growth stresses at
breast height level on the standing tree, on eight positions around the trunk. This tree
was typical of a strongly dissymmetrical distribution of growth stresses (Fig. 3). A
high local level of growth stress is always related to presence of tension wood
(Trénard & Guéneau 1975; Sassus 1994). Wood sample were taken around the
highest values of growth stress (Z position on Fig. 3). In spite of large G layer in the
fibre cell wall, S
2
layer remains thicker than in poplar wood (Fig. 4 B).
0
50
100
150
200
250
0 45 90 135 180 225 270 315
angular position of trunk periphery (in degree)
DRLM (µm)
selected beech typical low stressed beech
II
I
Z
Fig. 3: Growth stress measurement on standing beech tree, on 8 angular positions of
trunk periphery. I: tree with regular low levels of growth stress, II: tree with a zone
(Z) of very high tensile growth stress.
Fig. 4: SEM observation of poplar (A) and beech (B) with gelatinous layer (G)
(also indicated S
2
layer) (Scale bar: 20 µm)
Tension
Wood
A
B
G
S
2

4 IAWA Journal,
Wood samples were stored in green condition before further processing into small
blocks or thin sections.
Massive blocks
Wood sticks (2 cm in longitudinal direction, section 5 x 5 mm²)
are cut up by splitting in order to guarantee a good axial direction. Sticks were then
cut to obtain 5 mm size cubes. Finally a last superficial planning is done manually
with a brand new razor blade in order to produce a nice transverse surface, the
sample being always kept in moist condition.
Thin sections
Transverse sections, 80 µm thick, were cut under water drop with a
microtome equipped with disposable razor blade. These sections were glued on the
edge with fibre direction parallel to support, in order to allow observations on
transverse sections on both sides of the sample.
Scanning electron microscopy
Massive blocks or thin sections are dehydrated with absolute ethanol, passed to
critical point and coated (300 Å of platinum) before observation. Thus, observations
are made in oven dry condition with a Cambridge S360 Scan Electron Microscope
(Fig. 5).
The tilting of receptor allows to obtain images of a same object for different view
angles.
Fig. 5: SEM images of poplar: A massive bloc, B thin section; scale bars: 100 µm.
Atomic force microscopy
Smaller massive blocks (500 x 500 x 500 µm
3
), prepared the same way as before,
are observed in their transversal section in water and in air-dry condition. Four states
are studied: green condition, green condition after 2 hours in 80°C water, air-dry
conditions, wet conditions after air-drying. Atomic Force Microscope (Dimension
3100, Nanoscope IIIa, Digital Instruments) was used to obtain topographic images
of a 50 x 50 µm² area (around 10 cells). The same cells are observed successively in
these conditions (Fig. 6).
A B

Citations
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Journal ArticleDOI
TL;DR: This review presents a model of gelatinous-fibre organization and stresses the unique character of the gelatinous layer as a separate type of cell-wall layer, different from either primary or secondary wall layers.
Abstract: Gelatinous fibres are specialized fibres, distinguished by the presence of an inner, gelatinous cell-wall layer. In recent years, they have attracted increasing interest since their walls have a desirable chemical composition (low lignin, low pentosan, and high cellulose contents) for applications such as saccharification and biofuel production, and they have interesting mechanical properties, being capable of generating high tensional stress. However, the unique character of gelatinous layer has not yet been widely recognized. The first part of this review presents a model of gelatinous-fibre organization and stresses the unique character of the gelatinous layer as a separate type of cell-wall layer, different from either primary or secondary wall layers. The second part discusses major current models of tensional stress generation by these fibres and presents a novel unifying model based on recent advances in knowledge of gelatinous wall structure. Understanding this mechanism could potentially lead to novel biomimetic developments in material sciences.

163 citations


Cites background from "Shrinkage of the gelatinous layer o..."

  • ...Further, in atomic force microscopy analyses of cut surfaces of tension wood (kept under water to avoid drying effects) Clair and Thibault (2001) observed pronounced longitudinal shrinkage of the G-layer relative to S-layers, corresponding to a 4.7% strain, which is much greater than the recorded…...

    [...]


Journal ArticleDOI
TL;DR: Measurements show that mesoporosity is high in tension wood with a typical thick G-layer while it is much less with a thinner G- layer, sometimes no more than normal wood.
Abstract: The mechanism for tree orientation in angiosperms is based on the production of high tensile stress on the upper side of the inclined axis. In many species, the stress level is strongly related to the presence of a peculiar layer, called G-layer, in the fibre wall. The structure of G-layer has been recently described as a hydrogel thanks to N2 adsorption-desorption isotherms of supercritically dried samples showing a high mesoporosity (pores size from 2 to 50 nm). This led us to revisit the concept of G-layer that was until now only described from anatomical observation. Adsorption isotherms of both normal wood and tension wood have been measured on six tropical species. Measurements show that mesoporosity is high in tension wood with typical thick G-layer while it is much less with thinner G-layer, sometimes no more than normal wood. The mesoporosity of tension wood species without G-layer is as low as in normal wood. Not depending on the amount of pores, the pore sizes distribution are always centred around 6-12 nm. These results suggest that, among species producing fibres with G-layer, large structural differences of G-layer exist between species

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Cites methods from "Shrinkage of the gelatinous layer o..."

  • ...In previous research, the structure of the G-layer has been described as possessing gel-like characteristics: large shrinkage (Clair and Thibaut, 2001; Fang et al., 2007) and high rigidification during drying (Clair et al....

    [...]

  • ...In previous research, the structure of the G-layer has been described as possessing gel-like characteristics: large shrinkage (Clair and Thibaut, 2001; Fang et al., 2007) and high rigidification during drying (Clair et al., 2003)....

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Journal ArticleDOI
TL;DR: It is proposed that, during cellulose crystallization, a part of the xyloglucan is trapped inside the crystal, inducing longitudinal tensile stress within it; another part of it is accessible and present between the G-layer and the outer wall layers.
Abstract: †Background Tension wood evolved in woody angiosperms to allow stems with secondary thickening to bend and thus maintain an optimal orientation. Stem bending is the result of longitudinal tensile stress that develops in tension wood tissues. In many species, a specialized secondary cell wall layer, the so-called gelatinous (G)-layer, develops, containing longitudinally orientated crystalline cellulose fibrils; these have been recently shown to generate the tensile stress by an unknown mechanism. The cellulose fibrils cannot, however, work in isolation. Both coherence between the fibrils and adherence of the G-layer to the adjacent cell wall layers are required to transfer the tensile stresses of the cellulose fibrils to the tissue. Previous work had not identified hemicelluloses within the G-layer. †Recent Progress Sugar composition and polysaccharide linkage analyses of pure G-layers isolated by sonication have recently identified xyloglucan as the main non-cellulosic component of the G-layer. Xyloglucan has been detected by immunolabelling with the CCRC-M1 monoclonal antibody and by in-situ activity assays using XXXG‐sulforhodamine substrate in the developing G-layers but not in the mature ones. However, xyloglucan endotransglucosylase/hydrolase (XTH) proteins persist in the G-layer for several years and the corresponding xyloglucan endotransglucosylase (XET) activity (EC 2.4.1.207) occurs in the adjacent layers. Correspondingly, several XTHencoding transcripts were found to be up-regulated in developing tension wood compared with normal wood. †Scope We propose that, during cellulose crystallization, a part of the xyloglucan is trapped inside the crystal, inducing longitudinal tensile stress within it; another part of it is accessible and present between the G-layer and the outer wall layers. XET activity that occurs persistently in the G-fibres maintains coherence between the G-layer and the adjacent secondary wall layers. It is postulated that these activities are essential for generation of tensile stress during fibre maturation in tension wood.

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Abstract: The institutionalized separation between form, structure and material, deeply embedded in modernist design theory, paralleled by a methodological partitioning between modeling, analysis and fabrication, resulted in geometric-driven form generation. Such prioritization of form over material was carried into the development and design logic of CAD. Today, under the imperatives and growing recognition of the failures and environmental liabilities of this approach, modern design culture is experiencing a shift to material aware design. Inspired by Nature’s strategies where form generation is driven by maximal performance with minimal resources through local material property variation, the research reviews, proposes and develops models and processes for a material-based approach in computationally enabled form-generation. Material-based Design Computation is developed and proposed as a set of computational strategies supporting the integration of form, material and structure by incorporating physical form-finding strategies with digital analysis and fabrication. In this approach, material precedes shape, and it is the structuring of material properties as a function of structural and environmental performance that generates design form. The thesis proposes a unique approach to computationally-enabled form-finding procedures, and experimentally investigates how such processes contribute to novel ways of creating, distributing and depositing material forms. Variable Property Design is investigated as a theoretical and technical framework by which to model, analyze and fabricate objects with graduated properties designed to correspond to multiple and continuously varied functional constraints. The following methods were developed as the enabling mechanisms of Material Computation: Tiling Behavior & Digital Anisotropy, Finite Element Synthesis, and Material Pixels. In order to implement this approach as a fabrication process, a novel fabrication technology, termed Variable Property Rapid Prototyping has been developed, designed and patented. Among the potential contributions is the achievement of a high degree of customization through material heterogeneity as compared to conventional design of components and assemblies. Experimental designs employing suggested theoretical and technical frameworks, methods and techniques are presented, discussed and demonstrated. They support product customization, rapid augmentation and variable property fabrication. Developed as approximations of natural formation processes, these design experiments demonstrate the contribution and the potential future of a new design and research field. Thesis Supervisor: William J. Mitchell Title: Alexander Dreyfoos Professor of Architecture and Media Arts and Sciences Department of Architecture, MIT

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Abstract: Many biological materials have the property of being responsive to their environment combined with the ability to adapt to possible changes in this environment. Two prototypical responsive biological materials are presented and confronted with each other: bone and wood. These biomaterials have attracted research interest of materials scientists mainly investigating structure–property relationships. Ageing and diseases of bone and the widespread use of wood as construction material, fuel research from a medical and technological perspective. After describing the structure of bone and wood, the mechanisms of adaptation – adaptive growth and remodelling – are introduced, which allow structural changes in these biomaterials. Four examples are presented how these mechanisms are used for adaptation on different length scales starting from the shape at the macroscopic scale to the composite structure at the nanoscopic scale. In all these examples the biomaterials respond to mechanical stimuli and try to improve their mechanical performance. While some of the embarked strategies are very similar in bone and wood, like the arrangement of fibres and the architecture of the nanocomposite, differences can be observed in other situations like growing a supportive cylindrical structure or in the reorientation of structures. At the core of these differences is the capacity of living bone to deposit material where needed, but also to remove superfluous material. In contrast, a tree can only grow by adding new material.

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References
More filters

Book
01 Jan 1988
Abstract: Wood is formed in an essentially water-saturated environment in the living tree, and the cell wall remains in this state until the water flow from the roots is interrupted, such as by felling the tree. The wood then begins to lose most of its moisture by drying, resulting in changes in most of its physical properties. These changes, and their relationship to the environment to which the wood is subsequently ex posed, are the subject of this book. The text consists of six chapters. The first chapter discusses cer tain empirical relationships between wood and water, methods of measuring wood moisture content, factors which affect its equilib rium moisture content, and the effect of moisture content on wood strength. The second chapter treats the thermodynamics of moisture sorption by wood, inc1uding enthalpy, entropy, and free energy changes. The third chapter discusses some of the theories which have been proposed to explain the sorption isotherms for hygroscopic ma terials such as wood. Chapter 4 considers hygroexpansion or the shrinking and swelling of wood associated with moisture change. Chapter 5 is concerned with how moisture moves through the cell wall of wood in response to both moisture and temperature gradients. The sixth and final chapter discusses the theoretical and practical aspects of the electrical resistance and dielectric properties of wood, in c1uding the principles involved in their application in electrical moisture meters."

766 citations


"Shrinkage of the gelatinous layer o..." refers background in this paper

  • ...However, two cases exist when longitudinal shrinkage starts to be more important: in reaction wood (tension wood of angiosperms and compression wood of gymnosperms) and juvenile wood (Skaar 1988)....

    [...]

  • ...3 % in longitudinal direction, 3 % to 6 % in radial direction and from 6 % to 12 % in tangential one (Skaar 1988)....

    [...]

  • ...Between green condition and ovendry condition, shrinkage ranges from 0.05 % to 0.3 % in longitudinal direction, 3 % to 6 % in radial direction and from 6 % to 12 % in tangential one (Skaar 1988)....

    [...]


Journal ArticleDOI
Abstract: On the Longi tudinal Permeabi l i ty of Green Sapwood of Abies alba Miller and Piceaabies Karst. to Organic Solvents Summary Different organic solvents were passed through green cylindric samples of sapwood of Abies alba Miller and Picea abies Karst, at a pressure equal to 5 cm water column. By this means the factors influencing the rate of flow could be determined. 1. The rate of flow of an organic solvent is essentially dependent on its viscosity. 2. Although viscosity of the solvent influences the rate of flow especially at the onset of filtration, a high surface tension of the solvent can cause a continuous decrease of the rate of flow with the progress of the experiment. On the contrary a low surface tension effects only a small decrease in the rate of flow. 3. Hydrophobie solvents cannot be filtrated through untreated green sapwood even under application of a higher pressure. 4. For the solvents used here, no influence of the molecular size on the rate of flow is detectable.

153 citations


Journal ArticleDOI
Abstract: Introduction It is well known that when wood dries it shrinks very unequally in the three main directions. Kelsey (8) has given an excellent review of the subject and of theories that have been advanced. The present article attributes the anisotropy to the presence of crystalline microfibrils in the cell walls and attempts to predict mathematically how the shrinkage should depend on their orientation. Wood, particularly softwoods, may be thought of, with some idealisation, äs an aggregation of long parallel cells firmly bonded together by an amorphous material, the middle lamella. In the cells themselves one can distinguish a thin primary wall enclosing a thick threelayer secondary wall. These walls appear to be a mass of amorphous lignin and hemicelluloses in which are embedded long microfibrils of crystalline cellulose. In the middle layer of the secondary wall, which is the major part of the cell, the microfibrils are arranged in a steep helix around the cell axis, making some angle (from here referred to äs the microfibril angle) with the cell axis that may ränge from zero to perhaps 50° according to the species of tree and the position of the wood within the tree. The arrangement of microfibrils is not entirely regulär, they scatter somewhat in direction and it has been suggested that there are regions of greater or less disorder in the array (\"fringed micelle\" theory). On the walls lying parallel to the direction of the wood rays (the radial walls) the microfibrils wind past numerous pits which it has been suggested can lead to the effective microfibril angle being different from that in the walls lying at right angles to the direction of the wood rays (the tangential walls). It seems to be generally agreed that the amount of shrinkage and the anisotropy is governed in some way by the \"fine structure\" of the cell walls and the wood anatomy. There is, however, some divergence äs to what is meant by \"fine structure\". In this paper we are principally concerned with the part played by the cellulose microfibrils and in particular the way in which the shrinkage is affected by changes in the microfibril angle. Although, when the helical structure of the wall became known, it was expected that shrinkage anisotropy could be explained almost entirely in terms of the helix angle, this has not found favour with recent workers. Thus Boutelje (3) considers that the microfibril angle is a factor of only secondary importance. His picture of the cell wall is that it is a structure of concentric laminations and he suggests that the greater part of the adsorbed water is contained between these laminations. It is this laminate structure, he suggests, which leads to the transverse shrinkage anisotropy and to the very small amount of longitudinal shrinkage.

144 citations


Journal ArticleDOI
Abstract: To elucidate the origin of the shrinking anisotropy of wood during the drying process, as well as to begin to gain an understanding of the interaction between the moisture and the cell wall components, the shrinking process of a single wood fiber regarding water desorption was simulated by using an analytical model which was developed in the previous report (Part 1). Resulting data were compared with the experimental ones in this paper. The following conclusions were obtained: (1) The matrix substance, as a skeleton in the secondary wall, tends to shrink isotropically. However, the cellulose microfibrils, as a rigid framework of the cell wall, almost did not shrink at all due to the water desorption. As result, wood shrinks anisotropically during a drying process. The microfibril angle in the S2 layer is one of the most important factors related to the degree of shrinking anisotropy of the wood while drying. (2) According to the simulation, the expansive strain caused in the matrix skeleton by the water sorption increases by 15% (= 150,000 micro-strains) from the oven-dried condition to the green condition. Based on this value, the moisture content at the fiber saturation point is calculated to be about 35%, which is close to the experimentally obtained one. These results give quantitative evidences that the hygroexpansion of the wood cell wall is controlled by the mechanism of the reinforced matrix hypothesis.

93 citations


"Shrinkage of the gelatinous layer o..." refers background or methods in this paper

  • ...…other components properties (cellulose, hemicellulose and lignin), changes in matrix behaviour during drying and introducing the different cell wall layers have been proposed to refine this first theory (Barrett et al. 1972; Cave 1972b, 1978; Sassus 1998; Gril et al. 1999; Yamamoto 1999)....

    [...]

  • ...Later, other models integrating other components properties (cellulose, hemicellulose and lignin), changes in matrix behaviour during drying and introducing the different cell wall layers have been proposed to refine this first theory (Barrett et al. 1972; Cave 1972b, 1978; Sassus 1998; Gril et al. 1999; Yamamoto 1999)....

    [...]


Journal ArticleDOI
TL;DR: After considering both earlier evidence and the present results, it was concluded that the gelatinous layer has neither a honeycomb nor a homogeneous texture, as has been suggested, but that it consists of concentric lamellae of cellulose microfibrils.
Abstract: Pronounced tension wood from four North-American hardwood species has been examined by light and electron microscopy. Delignified fibers were also studied. The gelatinous layer was in all cases loosely attached to S2 but varied considerably in thickness within each species and was in one case terminated towards the lumen by a layer resembling S3. A terminal lamella was not observed. After considering both earlier evidence and the present results, it was concluded that the gelatinous layer has neither a honeycomb nor a homogeneous texture, as has been suggested, but that it consists of concentric lamellae of cellulose microfibrils. In the absence of hemicelluloses and lignin, the microfibrils are probably bound together less firmly than they are in other cell wall layers. The gelatinous layer is more readily separated from the remainder of the cell wall by mechanical forces than by chemical reagents.

76 citations