Showing papers in "Wood Science and Technology in 1977"
TL;DR: Later development, beginning with the dehydrogenation theory and experimental studies on the de-hydrogenative polymerization of p-hydroxycinnamyl alcohols, is reviewed in this article.
Abstract: Some pertinent results and views from the earlier history of lignin chemistry, pointing to the importance of the arylpropane skeleton, are outlined. Later development, beginning with the dehydrogenation theory and experimental studies on the dehydrogenative polymerization of p-hydroxycinnamyl alcohols, is then reviewed. Finally, recent degradative work resulting in a detailed picture of lignin structure is discussed.
1,586 citations
TL;DR: The structure of the reducing end group in xylan can be written: -β-D-Xylp-(1→4)-β- D-Xyphexylp(1→3)-α-L-Rhap-( 1→2)-α -D-GalpA-(1∆)-D-xyphex-hex-2enuronic acid as mentioned in this paper.
Abstract: The structure of the reducing end group in xylan can be written: -β-D-Xylp-(1→4)-β-D-Xylp-(1→3)-α-L-Rhap-(1→2)--α-D-GalpA-(1→4)-D-Xyl
In alkaline media the reducing xylose group is easily isomerized and removed by a β-elimination which leads to a reducing galacturonic acid end group. The 1, 2-linkage between rhamnose and the galacturonic acid explains the retarding effect on the alkaline peeling. Even under fairly mild conditions the galacturonic acid group is converted to other groups which are very stable in alkaline media. Model experiments permit the conclusion that OH-3 in the reducing group is subjected to β-hydroxyelimination. The 3-deoxy-2-O-α-L-rhamnopyranosyl-D-threo-hex-2-enuronic acid group formed is unstable in acid medium and escapes observation by the techniques employed for determination of the end groups.
Upon prolonged alkaline treatment and increased proportion of these groups is lost and a rapid peeling proceeds until a xylose group with a 4-O-methylglucuronic acid substituent is liberated. The consecutive reactions of this group are similar to those of the galacturonic acid groups.
The formation of 3-deoxyaldonic acid end groups, an important stopping reaction in cellulose, is of minor importance in xylan.
The financial support from the 1959 Ars Fond for Teknisk och Skoglig Forskning samt Utbildning is gratefully acknowledged.
137 citations
TL;DR: In this paper, a study on the shrinkage of wood representing the wide range of morphology variation in leaning trees was carried out on 13 trees of Eucalyptus regnans, one tree of Sieberi and four of Pinus radiata, and specimens taken at close intervals around the circumference of each stem.
Abstract: This is a study on the shrinkage of wood representing the wide range of morphology variation in leaning trees It involved 13 trees of Eucalyptus regnans, one of Eucalyptus sieberi and four of Pinus radiata, and specimens taken at close intervals around the circumference of each Data indicated a systematic modulation, between extremes at upper and lower sides of each stem, in longitudinal growth strains, relative proportions of thin, medium and thick-walled fibres, microfibril angle in the S2 layer of these, and both Klason and acid-soluble lignin content Analyses indicated that the microfibril angle in S2 was a prime factor in influencing both longitudinal and volumetric shrinkage reactions; proportion of thick-walled fibres in the tissue, thickness of S2 relative to S1, and variations in lignification also were involved Unusually thick-walled fibres were associated with visco-elastic strain recovery effects, which could form a substantial part of dimensional changes apparently attributable to shrinkage
64 citations
TL;DR: In this paper, a Freudenberg constitutional scheme for periodate lignin was proposed and the Freudenberg theory was applied to experimental results reported by Cousins on periodate Lignin.
Abstract: In previous papers, a theory was developed relating Young's modulus of hydrogenbond dominated solids to the density of this bond and to its parameters, and also to the moisture content of the solid. In this paper, the theory is applied to experimental results reported by Cousins on periodate lignin. The theory fits the observations and, furthermore, predicts that this particular lignin has 6.84 potential H-bonding sites per repeating unit of an assumed molecular weight of 1,000. No data for periodate lignin exist, but a Freudenberg constitutional scheme for lignin postulates a little over 7 potential sites for H-bonding per repeating unit of 1,000 molecular weight.
46 citations
TL;DR: In this article, the metabolic differences in the formation of guaiacyl and syringyl lignins were explained in terms of the different functions of O-methyltransferases and reducing enzymes which participate in methylation and reduction of the hydroxycinnamic acid intermediates in the biosynthetic pathway of these two types of lignin.
Abstract: Metabolic differences in the formation of guaiacyl and syringyl lignins were explained in terms of the different functions of O-methyltransferases and reducing enzymes which participate in methylation and reduction of the hydroxycinnamic acid intermediates in the biosynthetic pathway of these two types of lignins. Sinapyl alcohol was dehydrogenated with peroxidase and H2O2 under various reaction conditions. Chemical properties of the dehydrogenation polymers (DHPs) formed were characterized, and the possible occurrence of syringyl lignin in hardwood was discussed. DHP and dimers of p-coumaryl alcohol were also characterized and discussed in relation to the formation of grass lignin which contains p-hydroxyphenyl propane as an additional lignin monomer.
34 citations
TL;DR: Graphical models have been developed to represent X-ray diffraction patterns for microfibril arrangements in each of the characteristic secondary wall layers of fibres in normal earlywood, latewood, compression wood, and tension wood as discussed by the authors.
Abstract: Graphical models have been developed to represent X-ray diffraction patterns for microfibril arrangements in each of the characteristic secondary wall layers of fibres in normal earlywood, latewood, compression wood, and tension wood. Models for usual combinations of typical layers S1, S2, and S3, and for complex tissues including more than one S2 layer class indicate a basis for a new analytical technique for diffractograms.
22 citations
TL;DR: In this paper, the thickness variation of the secondary wall layers along a mature tension wood fiber was examined, using serial transverse sections, and that of the gelatinous layer along a differentiating fiber was also studied.
Abstract: The thickness variation of the secondary wall layers along a mature tension wood fiber was examined, using serial transverse sections, and that of the gelatinous layer along a differentiating fiber was also studied. In a mature gelatinous fiber the G-layer was the thickest in the central region of the fiber and decreased in thickness toward the tips. The thickness of the S2 layer also decreased from the center toward the tips, whereas the S1 layer showed a uniform thickness throughout the fiber length. From the observations of some differentiating fibers it was concluded that the G-layer possesses a uniform thickness along the length of a fiber at the earliest stage of G-layer formation and that the more the fiber develops, the greater is the reduction in thickness of the G-layer from the center of the fiber toward the tips. The thickening process of secondary wall layers is discussed.
14 citations
TL;DR: In this article, the composition of crude and purified lignins was evaluated with regard to non-hydrolyzable residue, acid-soluble lignin and polysaccharide content, which varied from 0.9 to 2.5%, depending on isolation conditions.
Abstract: Isolation of six milled wood lignins (MWL) from spruce under different conditions resulted in variable yields between 2.2% and 11.8% related to wood lignin. The composition of crude and purified lignins was evaluated with regard to non-hydrolyzable residue, acid-soluble lignin and polysaccharide content, which varied from 0.9 to 2.5%, depending on isolation conditions. The polysaccharide moiety of the crude and purified lignins contained a high percentage of glucose, probably derived from cellulose. The molecular size distributions determined by gel chromatography on different gels showed a broad distribution for all isolated lignins. A probable maximum of 40,000 for the molecular weight of milled wood lignins was determined by ultracentrifugation. Some of the lignin fractions were examined in the electron microscope.
14 citations
TL;DR: Tangential pit features were studied in a 55-year old black spruce (Picea mariana (Mill) B.S.P.) tree by means of light and electron microscopy as discussed by the authors.
Abstract: Tangential pit features were studied in a 55-year old black spruce (Picea mariana (Mill) B.S.P.) tree by means of light and electron microscopy.
13 citations
TL;DR: In this paper, it was shown that breaking of lignified covers of cell walls and fibrillar bundles by grinding increases the accessibility of the enzyme to the cellulose.
Abstract: Investigations on enzymic hydrolysis of cotton cellulose and spruce groundwood pulp with the multicomponent enzyme Onozuka SS have shown that lignin causes an almost total inhibition of the enzyme action. Breaking of lignified covers of cell walls and fibrillar bundles by grinding increases the accessibility toward the enzyme very effectively. Depolymerization of lignin is less important for improving the accessibility. The compact fibrillar structure of both cotton and wood cellulose also have an inhibitory effect on the penetration of the enzyme into the fiber. Beating loosens the compactness of the fibrillar structure and increases the accessibility. Only about 10% of the cellulose, probably highly crystalline, requires more drastic treatment e.g. ball-milling. Last units of polysaccharides linked to lignin in the lignin carbohydrate complex are resistant toward enzyme hydrolysis and require chemical cleavage. Total enzymic solubilization of lignified polysaccharides can therefore be attained only after a combined mechanical and chemical pretreatment.
13 citations
TL;DR: The physical properties and morphology of kraft paper handsheets obtained from tension wood of intensively managed, 5-year-old trees of Populus "Tristis No. 1" were compared to those produced from isolated normal wood of the same stems as mentioned in this paper.
Abstract: The physical properties and morphology of kraft paper handsheets obtained from tension wood of intensively managed, 5-year-old trees of Populus “Tristis No. 1” were compared to those produced from isolated normal wood of the same stems. Pulp yields of tension wood (TW) and normal wood (NW) were 60 and 53% respectively. Over a beating range of 0–45 minutes, strength properties of TW paper were in all cases noticeably inferior to those obtained from NW. During paper formation, the TW or gelatinous fibers resisted collapse, even upon extended refining, and produced thick, porous sheets of poorly bonded elements. It was concluded that the differential behavior of NW and TW pulps was in several respects analogous to those displayed by earlywood and latewood pulps, respectively, of softwood species as well as thin-vs. thick-walled hardwood fibers. Consequently, it appears that the inferior strength of TW paper is primarily a function of fiber morphology, and the difference in hemicellulose content between NW and TW (viz., lower pentosan content of TW) often cited in the literature as a potential major factor here probably contributes little if any significant effect on ultimate interfiber bonding and paper quality.
TL;DR: Mycelium of twenty species of wood-destroying fungi was cultivated in nutrient solutions with one of the following sugars as the only carbon source: glucose, arabinose, galactose, mannose and xylose.
Abstract: Mycelium of twenty species of wood-destroying fungi was cultivated in nutrient solutions with one of the following sugars as the only carbon source: glucose, arabinose, galactose, mannose and xylose. The growth of the species occurring in nature only on the wood of Angiosperms was equal or lower in the solutions with galactose and mannose than in the solution with glucose. The utilization of mannose was practically the same as that of xylose. The species which are specialized in nature in the wood of conifers grow better in the solutions with galactose and mannose, than in the solution with glucose; likewise mannose is beter utilized than xylose. Fungi attacking both kinds of wood do not exhibit any dependence on the utilization of the sugars used in these investigations.
TL;DR: In this article, the deformation and stresses in a circular wood log resulting from an arbitrary radial moisture distribution are examined, and the log is modeled as a layered cylinder, with each layer assumed to be linearly elastic, cylindrically orthotropic, and homogeneous.
Abstract: The deformation and stresses in a circular wood log resulting from an arbitrary radial moisture distribution are examined. In this paper the log is modeled as a layered cylinder, with each layer assumed to be linearly elastic, cylindrically orthotropic, and homogeneous. The general solution to the equations of elasticity for a representative layer is given; constants of integration in the solution are determined through application of appropriate continuity conditions at the layer interfaces. Numerical examples are presented for logs of Scots pine which illustrate the effect of nonuniform moisture content upon the displacement and stress distributions.
TL;DR: Warts have been observed in several bamboo species; they are present not only in vessel members and fibres, but also in the highly lignified parenchyma cells, especially in those of the elongated type.
Abstract: Warts have been observed in several bamboo species; they are present not only in vessel members and fibres, but also in the highly lignified parenchyma cells, especially in those of the elongated type. Among the 34 species studies only a few possess warts in all three cell types. The sizes of warts lie within the range observed for dicots and gymnosperms. There is no recognizable correlation between the occurrence of warts and the taxonomic grouping of bamboos. It has been suggested that the development of warts is associated with the lignification of the cell wall.
TL;DR: A large number of reducing xylose end groups are present in birch wood (Betula verrucosa) while all galacturonic acid moieties are non-reducing as discussed by the authors.
Abstract: A large number of reducing xylose end groups are present in birch wood (Betula verrucosa) while all galacturonic acid moieties are non-reducing. A large portion of the reducing xylose end groups are removed during treatments with alkali used for the islation of xylan, while reducing galacturonic acid moieties are formed by endwise degradation during this procedure.
TL;DR: The absence of microtubules during the main phase of secondary wall formation supports the view that differentiated tracheids in Pinus radiata D. Don are not involved directly in the biosynthesis of cellulose.
Abstract: Differentiating tracheids in Pinus radiata D. Don have been examined with the electron microscope. Despite the fact that one of the major differentiation processes is cellulose formation, little ultrastructural evidence has been found to indicate how this occurs. On the other hand, there is ample evidence of the incorporation of non-cellulosic material into both the expanding primary wall and the developing secondary wall. The only structure which could possibly be related to cellulose formation is a system of osmiophilic particles which have been found in the space between the plasmalemma and the developing wall, or attached to the most recently formed wall layer. The absence of microtubules during the main phase of secondary wall formation supports the view that these structures are not involved directly in the biosynthesis of cellulose.
TL;DR: In this article, a light and electron microscopical study of the removal of lignin during chlorite delignification and the changes in swelling during de-salting and alkali extraction was carried out on spruce wood.
Abstract: Cryo-ultramicrotomy was applied to holocellulose and alpha-cellulose from spruce wood (Picea abies Karst.) for a light and electron microscopical study of the removal of lignin during chlorite delignification and the changes in swelling during delignification and alkali extraction. The swelling state of the fibre walls during each stage of treatment was well preserved, and distinct differences could be observed. Staining with uranyl acetate brought out the fine structure of the fibre walls down to the range of elementary fibrils.
TL;DR: In this article, the xylem of straight Eucalyptus regnans trees of high growth stress was examined and radial dislocations in the secondary wall of many of the fibres were detected.
Abstract: Microscopical examination of the xylem of straight Eucalyptus regnans trees of high growth stress revealed the presence of radial dislocations in the secondary wall of many of the fibres. These features were characterized by a localized disruption in the microfibrillar orientation of the cellulose and were evident in both unlignified and lignified cell walls. Dislocations were not detected in trees having low peripheral growth stress. The origin of these features was suggested to lie in the expansion of the cell wall during the relaxation of longitudinal growth stresses following removal of the sample from the tree. A similar origin of the typically convoluted form of the gelatinous layer of tension wood fibres is discussed.
TL;DR: In this article, a modified fringe micelle diagram containing a considerable amount of chain association in the amorphous zones is given that meets the requirement dictated by the calculations of the monomolecular water vapor adsorption by three different celluloses from structural considerations.
Abstract: Calculations of the monomolecular water vapor adsorption by three different celluloses (cotton, wood pulp and cellophane) from structural considerations are in agreement with the BET determined values for crystallite diameters of 16 to 200 A on the basis of adsorption being confined to the fraction f of the three hydroxyl groups per anhydroglucose unit that are available on the surface of the crystallites and within the amorphous zones, when f ranges from 016 to 029 These low values of f are compatible with the fact that the void volume of the amorphous zones does not exceed about 6% More exact values for f are needed before more definite values for the crystallite diameters can be estimated A modified fringe micelle diagram containing a considerable amount of chain association in the amorphous zones is given that meets the requirement dictated by the calculations Another approach, involving direct estimation of the adsorbing surface areas of crystallites and amorphous zones, on the basis of adjacent surfaces being shared by water molecules adsorbed between them, gives surface areas somewhat larger than the BET values using the same f values Agreement with values from the former approach is obtained if only 75% of the surface per anhydroglucose unit is considered effective for adsorption
TL;DR: In this article, a technique was developed for the determination of the effective dissolved oxygen diffusivity in liquid-saturated softwood in a diffusion cell under ambient pressure, which was found to be 4.6 kcal/mole.
Abstract: A technique was developed for the determination of the effective dissolved oxygen diffusivity in liquid-saturated softwood in a diffusion cell under ambient pressure. From the measurements in the temperature range 2° to 50°C, the activation energy of diffusion was found to be 4.6 kcal/mole. The diffusivity in summerwood is about one half of that in springwood. The diffusivity of dissolved oxygen through composite springwood and summerwood layers was based upon samples of two Douglas fir sapwood blocks saturated with water. In the radial and tangential directions, diffusivity was 1.4 to 2.3x10-6cm2/s, which is about 6 to 10% that of dissolved oxygen diffusivity in water. The diffusivity in the longitudinal direction is about 5.5 times that in the other two directions. The diffusivity of dissolved oxygen through liquor-saturated wood and the effect of delignification on oxygen diffusion were also determined.
TL;DR: In this article, fast or abnormal (tumor) growth does not substantially affect wood substance and cell wall density, and void volume of dry cell walls is also not substantially affected.
Abstract: Fast or abnormal (tumor) growth does not substantially affect wood substance and cell wall density. Consequently, void volume of dry cell walls is also not substantially affected.
TL;DR: In this article, the authors used a three-dimensional finite element method to study how non-axisymmetric cuts affect the stress pattern of trees and showed that some oblique cuts reduce high stresses near the pith.
Abstract: Naturally-occurring growth stress patterns in timber are modified by cutting. Stresses in cut timber may cause destructive cracks and splits. This research uses a three-dimensional finite element method to study how non-axisymmetric cuts affect the stress pattern. The results show that some oblique cuts reduce high stresses near the pith. Experimental work supports the calculations.
TL;DR: In this paper, preliminary investigations were carried out aiming at the establishment of relationships between chemical, physical, and mechanical properties of beech wood under the influence of heating in water at 50°C and 100°C at pH values from 28 to 85 and with heating times up to 25 hours.
Abstract: Preliminary investigations were carried out aiming at the establishment of relationships between chemical, physical, and mechanical properties of beech wood under the influence of heating in water at 50°C and 100°C at pH values from 28 to 85 and with heating times up to 25 hours It was found that heating of beech wood in water at 50°C does not produce remarkable changes in its properties When green wood was heated at 100°C, insignificant changes in its density, shrinking, and α-cellulose content were observed, whereas a considerable decrease in strength was found when tested in a wet state It was further observed that on prolonged heating, the reactions of the wood and the solutions used as a heating medium under-went distinct changes, attaining an equivalent value approximating the final pH of the wood
TL;DR: In this article, the authors show that for axisymmetric geometries, while cracking may be reduced by making cuts of special shapes, a compensating amount of wood is destroyed by making the cut.
Abstract: Using the assumptions made on growth-stress related parameters in Part I, several optimization problems are posed. Finite element and optimization techniques show that for axisymmetric geometries, while cracking may be reduced by making cuts of special shapes, a compensating amount of wood is destroyed by making the cut. Also included in this study are banding of the log and stepped cuts with application of radial pressure. The results show that some combinations of radial pressure and the extent over which it is applied remove the most highly stressed wood.