Lignans are phenylpropanoid dimers, where the phenylpropane units are linked by the central carbon (C8) of their propyl side chains. Lignans vary substantially in the chemical structure of their basic carbon frameworks, oxidation levels, and aromatic substitution patterns. O-Methylation on the aromatic rings is often crucial in determining the final product distribution. In the secondary or specialized metabolic processes of plants, O-methylation is usually catalyzed by S-adenosyl-L- methionine-dependent O-methyltransferases (OMTs). We have so far isolated six cDNAs encoding lignan OMTs: Carthamus tinctorius matairesinol OMT (CtMROMT), Sesamum indicum OMT1 (SiOMT1), Sesamum radiatum OMT1 (SrOMT1), Anthriscus sylvestris matairesinol OMT (AsMROMT), A. sylvestris thujaplicatin OMT (AsTJOMT), and Forsythia koreana matairesinol OMT (FkMROMT). Phylogenetic tree analysis indicated that CtMROMT and AsMROMT formed a small clade with plant OMTs including caffeic acid O-methyltransferase from Rosa chinensis var. spontanea (RcOMT3) and reticuline 7-O-methyltransferase from Papaver somniferum (PsOMT1). By contrast, in the phylogenetic tree SiOMT1 and SrOMT1 were located closely to the clade containing 5-hydroxyconiferaldehyde OMTs ［CAldOMTs, caffeic acid OMTs (CAOMTs)］. AsTJOMT and FkMROMT were located in a small clade which is somewhat close to the clade of SiOMT1, SrOMT1, and CAldOMTs. In addition, two lignan OMT genes, PhOMT1 and PhOMT3, were detected in Podophyllum hexandrum that is known to produce an antitumor lignan, podophyllotoxin. PhOMT1 showed slight sequence similarity to AsTJOMT and FkMROMT, while PhOMT3 shared low sequence similarity with the other 7 lignan OMTs. These lignan OMTs show diverse substrate specificities and different meta/para selectivity in phenolic O-methylation. Taken together, the lignin OMTs may have arisen independently in various lignan-producing plants via acquisition of substrate specificity for lineage-specific lignan structures. These findings on lignan OMTs provide useful information for further identification of cDNAs encoding other lignan OMTs, as well as clues to understand diversity and plasticity of plant secondary metabolism beyond lignan biosynthesis.

The objective of this study was to investigate the effect of initial moisture content and steaming time of chips on medium density fiberboard (MDF) properties. Acacia mangium (Acacia mangium Willd.) chips with specific moisture content levels (10, 30, 60 and 90%) controlled in advance were steamed for 3 to 18 minutes under a steam pressure of 0.70 MPa before refining of fibers. In the case of chips with higher moisture content, the content of short fibers decreased and the modulus of rupture (MOR) of MDF increased by steaming. MOR and internal bond (IB) decreased with increased steaming time. It is presumed that the decrease was due to degradation of hemicellulose. It is concluded that high MOR values can be obtained by using chips with high moisture content and short steaming time when Acacia mangium is used as the raw material for MDF.

This work proposed a chemical pretreatment using a NaOH-thiourea aqueous solution at -5°C for modifying properties of a high yield mechanical pulp from moso bamboo (Phyllostachys pubescens). The effects of alkali dosage, of soaking time and of the following chilling time on the bamboo chips were evaluated. The optimal conditions were chosen as alkali dosage of 6%, soaking time of 15 min, and chilling time of 60 min. The refining energy of the bleached chemi-mechanical pulp was reduced by the chemical pretreatment using NaOH-thiourea aqueous solution, and further the screened yield, the brightness and the strength properties of the pulp were higher than those of the bleached mechanical pulp. However, there were no significant differences in the analysis of XRD and SEM between the NaOH-thiourea aqueous treated mechanical pulp and two bleached mechanical pulps.

For utilization of various biomass such as herbaceous tissue or leaves, a rapid and suitable lignin determination method is required. Here, we report a modification of the thioglycolic acid (TGA) method for rapid determination of lignin content in various samples. Our data demonstrated that 1 h instead of 16 h is enough to extract TGA lignin by NaOH, and no time but inverting is required to precipitate TGA lignin by concentrated HCl, indicating that the incubation time of the TGA method can be reduced from 23 h to 4 h. Lignin content in various samples determined by this rapid TGA (rTGA) method using absorbance at 280 nm was the same as with the conventional method. Furthermore, lignin obtained by the rTGA method was freeze-dried and weighed. This gravimetry of the rTGA (grTGA) method determined lignin content almost identical to that obtained with the Klason method in wood samples. Lignin contents of Japanese cedar leaves determined by the grTGA and Klason methods were 16.2% and 37.8%, respectively. The Wiesner reaction revealed that leaves of Japanese cedar have limited lignified tissue, suggesting that the grTGA method is more suitable for determining lignin in leaves. The grTGA method requiring no standard curve may be a rapid lignin determination method applicable to a wide variety of samples.

Wood identification of historical buildings is necessary not only to investigate the original wood species but also as part of other research such as the history of the buildings, the wood selection and the regional wood transportation. In 2016, a huge earthquake occurred in Kumamoto Prefecture, Japan, causing many historical buildings to collapse. Among the historical buildings which were affected, the valuable ”Western School Teacher^'s Hall” was completely destroyed. The aim of this study is to identify the wood species used for the building and to record and utilize this information for future reconstruction. Samples were taken from deteriorated members and hand sectioned samples were observed under an optical microscope. Then they were identified on the basis of microscopic anatomical features. As a result, it was revealed that 8 tree species, namely Cinnamomum camphora, Fraxinus sp., Zelkova serrata, Cryptomeria japonica, Chamaecyparis obtusa, Pinus subgen. Diploxylon, Thujopsis dolabrata and Kalopanax septemlobus were used. Our results would provide basic information for future restoration.

Durability performance of nailed joints of wood-based panels is of importance in structural applications. In this study, the effect of timing of nailing during accelerated aging treatment on the nailed joint performance of particleboard and plywood was investigated. The retention of lateral nail resistance (LNR) and nail head pull-through (NHP) for the Dry-1 condition, where nailing was performed before accelerated aging treatment, kept almost same value as those for the Dry-2 condition, where nailing was performed after accelerated aging treatment. These results showed that the timing of nailing during accelerated aging treatment did not affect LNR and NHP. On the other hand, nail withdrawal resistance (NWR), as defined by ASTM, for the Dry-1 condition was clearly lower than that for the Dry-2 condition.

In order to develop 2-hour-fireproof cross laminated timber (CLT) floor and wall structures, covering them with wood impregnated with fire-retardant agent was studied. In the fire test of the CLT wall specimen, two layers of fire-retardant impregnated wood (Cryptomeria japonica D. Don) were alternately laminated with screws to the load-bearing CLT and a fire test was conducted for 2 hours. The total thickness of the covering material was 90 mm. However, the CLT burned due to early drop-off of the top layer and shrinkage of the second layer, and the wall specimen did not show 2-hour fire-resistance performance. Based on this test result, in the fire test of the floor, the covering material was specified as a fire-retardant impregnated wood panel of three layers of 30 mm thick treated wood and a 10 mm thick untreated wood layer laminated and bonded together with adhesives. The panels were joined by two types of spline made of fire-retardant impregnated wood, and were attached to the CLT with screws. The screw holes were filled with untreated wood. In the 2 hour-fire tests of the floor specimens, flames died out and charring stopped in the covering layer. This result shows that covering with fire-retardant impregnated wood panels makes the CLT 2-hour fireproof.