This study is focused on what factor mainly affects the mechanical properties of each wood species in the lateral direction. At first, the influence of the density which is closely related to mechanical properties in the longitudinal direction was also researched in the lateral direction. Thus, the elastic modulus, strength, and failure strain in the lateral tension were measured using thin cross-sectional samples of softwoods and hardwoods, having wide varieties in the density and anatomical features. The results obtained are as follows. The linear relationship between the density and the elastic modulus which has been verified in the longitudinal direction was not observed in the lateral tension for the samples with the annual ring inclination of 90°, which samples were influenced by ray arranged parallel to the tensile direction. However, samples with the annual ring inclination of 45° showed the high correlation between the density and the elastic modulus due to the shearing deformation of the cell shape. On the other hand, the proportional relationship between the elastic modulus and strength which has been verified in the longitudinal direction was not observed in the lateral tension except for the samples with the annual ring inclination of 90°. From the results obtained, it was revealed that the mechanical properties of wood in the lateral direction were significantly affected not only by the density but also by the structural features such as deformation of cell shapes, arrangement of ray or vessels, and the degree of the transition from the earlywood to the latewood.
As an effective utilization method of the oil palm trunks, particleboards were prepared using vascular bundles of the trunks. The vascular bundles were obtained by separating parenchyma from a trunk veneer using a hammer mill. The boards with density of 0.6 g/cm 3 , 0.7 g/cm 3 and 0.8 g/cm 3 and with resin content of 5%, 10% and 15% were prepared and comparatively evaluated. Isocyanate was used as an adhesive. Modulus of rupture, modulus of elasticity and thickness swelling of the specimens taken out from each board were measured according to JIS A 5908. Following results were obtained. 1) More than 90% of the particles were 20 mm to 50 mm in length. The particles of 20 mm to 30 mm accounted for 35% of the total. Some particles contained parenchyma, attached to the surface of a vascular bundle, but most of particles were vascular bundles only. 2)MOR of specimens obtained from a board with resin content of 10% or more sufficiently satisfied JIS A 5908. MOR and MOE of a board with resin content of 10% or 15% increased with increasing resin contents and densities on boards. The fracture strains were not changed with the resin contents and densities. MOR and MOE of the specimens obtained from boards with all conditions were higher than those prepared from purely oil palm trunk. 3)Thickness swelling of the specimens obtained from a board with resin content of 10% or more sufficiently satisfied JIS A 5908. Thicknesses swelling of the specimens obtained from board with all conditions were lower than coefficient of swelling of those prepared from purely oil palm trunk in the radial direction.
Background: Plant pathogens secrete enzymes that degrade plant cell walls to enhance infection and nutrient acquisition. Results: A novel endotransglucosylase catalyzes cleavage and transfer of -glucans and decreases the physical strength of plant cell walls. Conclusion: Endotransglucosylation causes depolymerization and polymerization of -glucans, depending on substrate molecular size. Significance: Enzymatic degradation of plant cell walls is required for wall loosening, which enhances pathogen invasion.
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