The quantity and quality of wood are controlled by cambial cell division and the process of xylem differentiation of cambial derivatives. This paper summarizes cell biological and tree physiological observations to understand the mechanism of regulation of wood formation. In particular, the roles of plant hormones in the control of seasonal changes in cambial activity are reviewed.

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The objective of the present study is to clarify the effects of smoke drying, this method of which has been used for drying plain wood for making lacquer ware, on wood property. Logs 35 cm in length were smoke-dried for 30 to 90 days. After drying, moisture content (MC), equilibrium moisture content (EMC), relative degree of crystallinity (RDC) of cellulose, mean shrinkage at 1% MC decrease, and static bending property and impact bending properties were investigated. During smoke drying for 90 days, mean and maximum temperature inside the treatment chamber were 33°C and 58°C, respectively, while mean and maximum temperature inside the log were 30°C and 45°C, respectively. Heartwood and sapwood showed almost the same MC of about 10%. There were no significant differences in EMC and RDC between naturally dried wood and smoke-dried wood. Mean shrinkage at 1% MC decrease in the radial and tangential directions of smoke-dried wood showed low values compared to those of naturally dried wood. In addition, specific Young's modulus in static bending increased with increasing duration of smoke-drying. These results suggest that decreased shrinkage in the radial direction and increased specific Young's modulus in static bending may result in increased quality of plain wood for lacquer ware.

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The contribution of lignin to the adsorption of several kinds of organic liquids onto wood was studied in relation to the amount of residual lignin of the samples. Three alcohols of different molecular size and dimethyl sulfoxide (DMSO), which was suggested to have a strong affinity for dry lignin in the preceding paper, were used as organic liquids. Dry and preswollen samples prepared by gradual delignification from wood meal were used as adsorbents. The results obtained were as follows : as the delignification progressed, the amount of adsorption of ethanol onto dry samples decreased remarkably, while the amount of adsorption of methanol hardly decreased. This means that vacant pores and/or adsorption sites loosely hydrogen-bonded to each other (which were suggested to exist in dry lignin in the preceding paper) are accessible to liquids having similar molecular sizes as ethanol. The amount of alcohols adsorbed onto preswollen samples increased in the final stage of delignification. This suggests that lignin contributes restraint of swelling of cellulose and/or hemicellulose in wood. The adsorbed amount of DMSO decreases with progressive delignification not only on dry samples but also on preswollen samples. Therefore, it can be concluded that DMSO has stronger affinity for lignin than for cellulose and hemicellulose not only in the dry wood but also in the preswollen wood.

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Wooden I-beams with Todomatsu (Abies sachalinensis) lumber and Karamatsu (Larix kaempferi) plywood were developed to meet the demand for a stable and quality controlled supply of floor framing members for wood frame construction from plantation timber resources. In this study, wooden I-beams of 235 mm depth and three flange sizes were manufactured by common wood working machines, and their bending, shear and partial bearing properties were examined. The tolerance limits of bending and partial bearing properties of the I-beams developed in this study were equal to or higher than those of dimension lumber with the same beam depth, although statistical analyses showed that their characteristic values were lower than those of North American I-beams of similarly shaped cross sections with MSR lumber flanges and OSB webs. From the results of examination, it was confirmed that the I-beams developed in this study could be satisfactorily substituted for dimension lumber of the same depth as joists and rafters for wood frame construction under ordinary loads, although careful consideration should be given to exceptional cases when shear force is critical in the structural design.

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Recently, it has been reported that bamboo is sometimes used as a raw material in some of kraft pulp mills. However, there are few findings on relationships between chemical features and cooking or bleaching response. In this study, Phyllostachys pubescens which was obtained in Ibaraki prefecture was chemically analyzed, and kraft-cooked and bleached by totally chlorine-free (TCF) bleaching. In addition, P. pubescens stems were compared with Hibiscus cannabinus bast, Cryptomeria japonica D. Don wood and Eucalyptus grandis wood. The lignin content of P. pubescens stems was similar to that of E. grandis wood, and the xylan content of P. pubescens was high compared with the other materials. In obtaining pulps with given kappa numbers, the delignification response of P. pubescens was equal to that of E. grandis and better than that of H. cannabinus bast. However, the pulp yield of P. pubescens was lower than that of E. gradis or H. cannabinus bast, and was equal to that of C. japonica. The hexenuronic acid ontent of P. pubescens kraft pulp was lower than that of H. cannabinus bast or E. grandis. The brightness of unbleached pulp prepared from P. pubescens was far higher than that from H. cannabinus and E. grandis. The P. pubescens pulp gave higher brightness after oxygen bleaching than the H. cannabinus or E. grandis pulps.

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