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.

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.

Degradation of the Gelatinous Layer in Aspen and Rubberwood by the Blue Stain Fungus Lasiodiplodia Theobromae

IAWA Journal ◽  
1997 ◽  
Vol 18 (2) ◽  
pp. 107-115 ◽  
Author(s):  
Osvaldo Encinas ◽  
Geoffrey Daniel
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Tension Wood ◽  
Soluble Carbohydrates ◽  
Tropical Species ◽  
Cell Wall Degradation ◽  
Lasiodiplodia Theobromae ◽  
Gelatinous Layer ◽  
Weight Losses ◽  
Blue Stain

Studies on the degradative ability of the blue stain fungus Lasiodiplodia theobromae (Pat.) Griffon ' Maublanc have shown several strains to cause significant weight losses (c. 20%) in wood of temperate and tropical species, aspen (Populus tremula) and rubberwood (Hevea brasiliensis), both species that commonly form tension wood. In addition to the consumption of soluble carbohydrates, major changes occurred in the ultrastructure of fibre cell walls, with a rapid attack of the G-layer of the gelatinous fibres. Following G-layer degradation, earlywood fibres of both species showed true cell wall degradation with pronounced erosion attack, suggesting that prior destruction of the G-layer afforded greater accessibility and ease of attack of the outer secondary cell wall layers.

Cell Wall Morphogenesis and Structure in Tropical Tension Wood

IAWA Journal ◽  
1986 ◽  
Vol 7 (2) ◽  
pp. 155-164 ◽  
Author(s):  
Beatrice Satiat-Jeunemaitre
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Tension Wood ◽  
Ultrastructural Cytochemistry ◽  
Fibre Cell ◽  
Gelatinous Layer ◽  
Wall Deposition ◽  
Growth Constraints ◽  
Cell Wall Morphogenesis ◽  
Cell Wall Deposition

Differentiating tension wood was observed in order to analyse the changes occurring during cell wall morphogenesis. Specimens were taken from trees in Guyana. Wall texture was analysed by means of ultrastructural cytochemistry. Modifications were encountered in fibre and vessel walls of tension wood when compared to typical wood. The changes were twofold: variation in the layering of polylamellate walls, and the deposition of a gelatinous layer in the fibre cell walls. Results are discussed in terms of variations in the rhythmic nature of cell wall deposition. Data confirm that the morphogenesis of the wall is a modular process allowing the cells to adapt to growth constraints.

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.

Lignin distribution in mild compression wood of Pinus radiata

1999 ◽  
Vol 77 (1) ◽  
pp. 41-50 ◽  
Author(s):  
Lloyd A Donaldson ◽  
Adya P Singh ◽  
Arata Yoshinaga ◽  
Keiji Takabe
Keyword(s):  
Cell Wall ◽  
Fluorescence Microscopy ◽  
Pinus Radiata ◽  
Compression Wood ◽  
Middle Lamella ◽  
Confocal Fluorescence Microscopy ◽  
Interference Microscopy ◽  
Normal Wood ◽  
Lignin Distribution ◽  
Confocal Fluorescence

Lignin distribution in the tracheid cell wall of mild compression wood in Pinus radiata D. Don was examined by interference microscopy, confocal fluorescence microscopy, and ultraviolet (UV) microscopy. Two anatomically different samples of mild compression wood were compared with a sample of normal wood using quantitative interference microscopy and microdensitometry combined with confocal fluorescence microscopy to estimate the quantitative or semiquantitative lignin distribution in the S2 and S2L regions of the secondary cell wall and of the cell corner middle lamella (CCML). One of these samples was briefly examined by UV microscopy for comparison. Quantitative interference microscopy provided information on lignin concentration in different regions of the cell wall with values of 26, 46, and 57%, respectively, for the S2, S2L, and CCML regions of sample 1 and 20, 29, and 46%, respectively, for the same regions of sample 2. Microdensitometry of confocal fluorescence images provided semiquantitative information on the relative lignin distribution based on lignin autofluorescence. Comparison between the two compression wood samples using autofluorescence gave results that were in partial agreement with interference microscopy with respect to the relative lignification levels in the S2, S2L, and CCML regions. Some improvement was achieved by using calibration values for hemicellulose rather than holocellulose for interference data in the S2L region. Results for UV microscopy performed on sample 1 indicated that the lignification of the CCML region was comparable with that of the S2L region in this sample but with some variation among cells. All three techniques indicated significant variation in lignification levels of the S2L and CCML regions among adjacent cells and a significant reduction in the lignification of the CCML region compared to normal wood.Key words: lignin distribution, interference microscopy; confocal fluorescence microscopy, UV microscopy, mild compression wood, Pinus radiata D. Don.

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