Ugai Watanabe

The importance of seasonal differences in the cellulose microfibril angle in softwoods in determining acoustic properties

The influence of the micro- and mesoscopic structure of wood cell walls on the acoustic properties of softwood was investigated in a synchrotron X-ray microbeam diffraction experiment with particular attention to the seasonal differences in crystallographic features. A multiple regression analysis was performed for data from 12 different softwood species in order to determine the dependence of longitudinal relative Youngs modulus (E/ρ) and loss tangent (tanδ) on seasonal cellulose microfibril angles (MFAs), crystal width of cellulose microfibrils etc. We conclude that a low MFA in both latewood and earlywood yields high E/ρ and low tanδ, which is an attribute of wood used as violin or piano soundboards. Among the softwood species we characterized Sitka spruce best fits this criterion.

Tangential Young's modulus of coniferous early wood investigated using cell models

Summary The relationship between the tangential Youngs modulus and the transverse cell shape in coniferous early wood was investigated by using cell models constructed by power spectrum analysis. The calculated Youngs moduli of the cell models explained qualitatively the change of the experimental Youngs moduli with density as well as the difference in the experimental values among species. The calculated Youngs moduli differed significantly among species depending on the cell model shapes when compared at the same density. With increasing element angle in the model, the Youngs modulus greatly increased without a significant change in the density, especially at the larger ratios of the axial length of the tangential cell wall to that of the radial cell wall.

Transverse Young's Moduli and Cell Shapes in Coniferous Early Wood

Summary The relationship between transverse Youngs moduli and cell shapes in coniferous early wood was investigated using cell models constructed by two dimensional power spectrum analysis. The calculated values of tangential Youngs modulus qualitatively explained the relationship between experimental values and density as well as the difference in experimental values among species. The calculated values of radial Youngs modulus for the species having hexagonal cells agreed well with the experimental values, whereas, for the species having square cells, the calculated values were much larger than the experimental values. This result was ascribed to the fact that the bending moment on the radial cell wall of square cell models was calculated to be small. It is suggested that the asymmetrical shape of real wood cells or the behavior of nodes during ell deformation is an important factor in the mechanism of linear elastic deformation of wood cells.

Liquid penetration of precompressed wood VI: Anatomical characterization of pit fractures

Pit fractures of refractory coniferous heartwoods caused by precompression in the radial direction were investigated and are discussed in terms of improved liquid penetration. Small cracks appeared at the boundary between the torus and margo, along the outer margin of the margo, and on the torus when specimens were compressed and deformation was fixed by drying. The remarkable cracks were generally observed for Cryptomeria japonica D. Don. Pseudotsuga menziesii Franco showed peculiar detachment of the torus from the pit border, and Larix leptolepis Gordon exhibited only small cracks on the torus. These fractures patterns were clearer when the precompressed specimens were recovered by water impregnation and then redried.

Cell wall thickness and tangential Young's modulus in coniferous early wood

To investigate the effect of wall thickening around cell corners on the tangential Youngs modulus of coniferous early wood, tapered beam cell models in which the variation of the cell wall thickness in the axial direction was taken into account were constructed for seven species. Their tangential Youngs moduli were compared with the experimental results. The calculated Youngs moduli of tapered beam cell models were larger than those of the models composed of the cell walls with uniform thickness, although both models showed almost the same density. For some species the calculated Youngs moduli of the models in which the cell wall thickness increased curvilinearly in the axial direction were much closer to the experimental values. The reduction of the radial cell wall deflection due to the increase of the stiffness around cell corners was considered to increase the tangential Youngs modulus of a wood cell.

Liquid penetration of precompressed wood VII: combined treatment of precompression and extraction in hot water on the liquid penetration of wood

The object of this study was to determine the cause of differences in the improvement in liquid penetration of precompressed wood species. The maximum amount of water uptake by the capillary rise method and changes in the aspirated pits seen with scanning electron microscopy before and after of preextraction and precompression were investigated using heartwood samples of four softwoods. The height of penetration and the weight by the capillary rise method for preextractive wood powders are discussed. Three wood species andLarix leptolepis showed marked increases in the amount of solution uptake after precompressed treatment only.Larix leptolepis wood required compression after extraction by boiling in water. These differences among wood species were caused by the accumulation of extractive material. It was also recognized that the accumulative material inLarix wood has plasticity and that inPseudotsuga is brittle. Based on these results it was found that it is difficult to destroy aspirated pits in the former and easy in the latter. On the other hand, the difference in penetration of each wood species was caused by the quantity and quality of the extraction material in addition to the extent of the wettability of the surface of the cell cavity as well as aspirated pit.

Transverse shrinkage of coniferous wood cells examined using replica method and power spectrum analysis

The shrinkage behavior of coniferous wood cells was investigated by the power spectrum analysis as well as by the replica method. During drying, cell lumens shrank in normal wood and expanded in compression wood, depending on their cell wall structures. The tracheids of Agathis bornensis with no distinct growth rings also showed the anisotropic shrinkage. The representative cell models before and after shrinkage constructed by the power spectrum analysis revealed that the difference in the anisotropic shrinkage among wood species greatly depended on their transverse cell shapes.

Seasonal variation in formation, structure, and chemical properties of phloem in Picea abies as studied by novel microtechniques

AbstractMain conclusionPhloem production and structural development were interlinked with seasonal variation in the primary and secondary metabolites of phloem. Novel microtechniques provided new perspectives on understanding phloem structure and chemistry. To gain new insights into phloem formation in Norway spruce (Picea abies), we monitored phloem cell production and seasonal variation in the primary and secondary metabolites of inner bark (non-structural carbohydrates and phenolic stilbene glucosides) during the 2012 growing season in southern and northern Finland. The structure of developing phloem was visualised in 3D by synchrotron X-ray microtomography. The chemical features of developing phloem tissues isolated by laser microdissection were analysed by chemical microanalysis. Within-year phloem formation was associated with seasonal changes in non-structural carbohydrates and phenolic extractive contents of inner bark. The onset of phloem cell production occurred in early and mid-May in southern and northern Finland, respectively. The maximal rate of phloem production and formation of a tangential band of axial phloem parenchyma occurred in mid-June, when total non-structural carbohydrates peaked (due to the high amount of starch). In contrast, soluble sugar content dropped during the most active growth period and increased in late summer and winter. The 3D visualisation showed that the new axial parenchyma clearly enlarged from June to August. Sub-cellular changes appeared to be associated with accumulation of stilbene glucosides and soluble sugars in the newest phloem. Stilbene glucosides also increased in inner bark during late summer and winter. Our findings may indicate that stilbene biosynthesis in older phloem predominantly occurs after the formation of the new band(s) of axial parenchyma. The complementary use of novel microtechniques provides new perspectives on the formation, structure, and chemistry of phloem.

Transverse shrinkage anisotropy of coniferous wood investigated by the power spectrum analysis

The transverse shrinkage behavior of early wood and late wood tracheids of radiata pine (Pinus radiata D. Don) was investigated by the power spectrum analysis. The representative cell model shapes before and after shrinkage constructed by the analysis revealed that the early wood tracheid showed anisotropic shrinkage, although the late wood tracheid showed almost isotropic shrinkage. To link the macroscopic shrinkage of coniferous wood with the results obtained by the power spectrum analysis, a two-layer model composed of early wood and late wood was adopted, and the relation between shrinkage anisotropy and late wood fraction was predicted. The results suggested that the shrinkage anisotropy depended significantly on the mechanical interaction between early and late wood.

Drying and anatomical characteristics of sugi wood attacked by bacteria during pond storage

Seven species of bacteria were isolated and identified from ponded sugi (Cryptomeria japonica D. Don) logs, and six species showed potent wood-degrading activities. To evaluate the effects of these isolated bacteria on the drying and anatomical characteristics of wood, small fresh blocks of sugi were immersed in water suspensions containing bacteria for 1–7 months. The permeability and drying properties were evidently improved. Most of the encrusting substances adhering to the cell lumens and the pit chambers were removed, and the pit membranes were destroyed. These anatomical changes due to bacterial activity were assumed to improve the permeability of sugi wood.