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Volker Haag, Gerald Koch, Hans-Georg Richter, Robert Evans, José Antonio Silva Guzmán and Uwe Schmitt

Edited by Lloyd A. Donaldson

ABSTRACT

Anatomical and subcellular characteristics of juvenile and adult wood of seven species (Manilkara zapota (L.) P. Royen, Platymiscium yucatanum Standl., Lonchocarpus castilloi Standl., Roseodendron donnell-smithii (Rose) Miranda, Terminalia buceras (L.) Wright, Tabebuia rosea (Bertol.) DC., Lysiloma latisiliquum (L.) Benth. from Mexico, including a histometric evaluation, were investigated by light microscopy with a digitized image analysis system and by X-ray diffractometry using the SilviScan® system. The topochemical distribution of lignin and phenolic deposits in the tissue was studied by means of cellular UV-microspectrophotometry (UMSP). Extractive contents (acetone/water and water) were determined gravimetrically. The results of the structural and topochemical analyses were compared with the interrelations of certain anatomical and subcellular structures as well as the topochemical composition with regard to the physical and mechanical properties of the timbers investigated. The objective was to provide a detailed cellular and subcellular description of the heartwood of seven lesser-known timbers from Central America. All examined tree species show significant differences between juvenile and adult heartwood. For individual species, however, the differences vary greatly and have to be individually assessed in addition to general trends observed for all studied species. It has been shown that vessel size, fibre length, size of fibre lumina, and height and width of rays, as well as the content of extractives and topochemical composition of the cell walls, are suitable indicators for the differentiation of the two heartwood types. The results also contribute to a better understanding of the wood properties of the investigated timbers in relation to their utilization and added value increase.

Shahanara Begum, Osamu Furusawa, Masaki Shibagaki, Satoshi Nakaba, Yusuke Yamagishi, Joto Yoshimoto, Md Hasnat Rahman, Yuzou Sano and Ryo Funada

Edited by Lloyd A. Donaldson

ABSTRACT

The aim of the present study was to investigate the orientation and localization of actin filaments and cortical microtubules in wood-forming tissues in conifers to understand wood formation. Small blocks were collected from the main stems of Abies firma, Pinus densiflora, and Taxus cuspidata during active seasons of the cambium. Bundles of actin filaments were oriented axially or longitudinally relative to the cell axis in fusiform and ray cambial cells. In differentiating tracheids, actin filaments were oriented longitudinally relative to the cell axis during primary and secondary wall formation. In contrast, the orientation of well-ordered cortical microtubules in tracheids changed from transverse to longitudinal during secondary wall formation. There was no clear relationship between the orientation of actin filaments and cortical microtubules in cambial cells and cambial derivatives. Aggregates of actin filaments and a circular band of cortical microtubules were localized around bordered pits and cross-field pits in differentiating tracheids. In addition, rope-like bands of actin filaments were observed during the formation of helical thickenings at the final stage of formation of secondary walls in tracheids. Actin filaments might not play a major role in changes in the orientation of cortical microtubules in wood-forming tissues. However, since actin filaments were co-localized with cortical microtubules during the formation of bordered pits, cross-field pits and helical thickenings at the final stage of formation of the secondary wall in tracheids, it seems plausible that actin filaments might be closely related to the localization of cortical microtubules during the development of these modifications of wood structure.

Jong Sik Kim and Geoffrey Daniel

Edited by Lloyd A. Donaldson

ABSTRACT

Although there is considerable information on the chemistry of gelatinous (G) layers in tension wood (TW) fibers consisting of S1+S2+G cell wall structure (poplar), little is known on the chemistry of G-layers in TW fibers organized with S1+G structure. This study investigated the distribution of lignin and non-cellulosic polysaccharides in ash TW fibers (S1+G) using histochemistry and immunolocalization methods. TW fibers studied were fully developed (mature fibers) and obtained from two (TW-1, TW-2) mature European ash trees (Fraxinus excelsior L.). Based on differences in microfibril angle (MFA) and TW trees used, TW fibers were mainly classified into three types; 1) Type-1 fibers with MFA almost parallel to the fiber axis that were found in TW-1, 2) Type-2 fibers with 12° MFA that were abundant at the end of growth rings of TW-1 and 3) Type-3 fibers with 10° MFA that were found in TW-2. The S3 layer was absent in all TW fibers. In this study, the secondary cell wall structure of Type-1 and Type-2/Type-3 fibers were defined as G and GL (gelatinous-like) layers, respectively. Lignin with syringyl (S) units was detected in G/GL-layers, in which intensity and patterns of lignin staining likely related to the difference in MFA between G- and GL-layers. With hemicelluloses, heteroxylan and heteromannan epitopes were detected in G/GL-layers but these were much less abundant than those in S2 layers of normal wood (NW) fibers. Like lignin, distribution patterns of heteromannan epitopes in G/GL-layers likely related to differences in MFA between fiber types. Sparse xyloglucan epitopes were also detected in G/GL-layers. Homogalacturonan epitopes were absent in G/GL-layers. All fiber types showed abundant a-1, 5-arabinan epitopes in G/GL-layers. Overall results indicate that the chemistry of ash TW fibers studied differs significantly from that of other species reported previously, specifically TW fibers composed of S1+S2+G structure.

Jie Wang, Liping Ning, Qi Gao, Shiye Zhang and Quan Chen

Edited by Lloyd A. Donaldson

ABSTRACT

The subject of this study is the structure and composition of buried Phoebe zhennan wood. Through comparative studies of the anatomy and composition with modern undegraded wood, the objective was to understand any changes that have taken place in the P. zhennan buried wood samples. The P. zhennan buried wood can be identified by wood structure characteristics and volatile components analysis. It is required that the microstructural features are identical to those of modern P. zhennan wood; simultaneously, the volatile components of the wood must contain six characteristic compounds with the same peak retention time. The P. zhennan buried wood sample which was used in the experiment was dated 8035–7945 BP (95.4% probability). Further research showed that the cell wall of P. zhennan buried wood had been damaged, the hemicellulose was heavily degraded but there was no obvious degradation of crystalline cellulose. Moisture was present mainly as free water and large amounts of mineral elements such as Fe, and Ni were detected in the ash of P. zhennan buried wood. Both the buried and modern wood of P. zhennan were acidic.

Lloyd Donaldson, Adya Singh, Laura Raymond, Stefan Hill and Uwe Schmitt

ABSTRACT

Douglas-fir (Pseudotsuga menziesii) has distinctly colored heartwood as a result of extractive deposition during heartwood formation. This is known to affect natural durability and treatability with preservatives, as well as other types of wood modification involving infiltration with chemicals. The distribution of extractives in sapwood and heartwood of Douglas-fir was studied using fluorescence microscopy. Several different types of extractive including flavonoids, resin acids, and tannins were localized to heartwood cell walls, resin canals, and rays, using autofluorescence or staining of flavonoids with Naturstoff A reagent. Extractives were found to infiltrate the cell walls of heartwood tracheids and were also present to a lesser extent in sapwood tracheid cell walls, especially in regions adjacent to the resin canals. Förster resonance energy transfer measurements showed that the accessibility of lignin lining cell wall micropores to rhodamine dye was reduced by about 50%, probably as a result of cell wall-bound tannin-like materials which accumulate in heartwood relative to sapwood, and are responsible for the orange color of the heartwood. These results indicate that micro-distribution of heartwood extractives affects cell wall porosity which is reduced by the accumulation of heartwood extractives in softwood tracheid cell walls.

Shuqin Zhang, Rong Liu, Caiping Lian, Junji Luo, Feng Yang, Xianmiao Liu and Benhua Fei

Edited by Lloyd A. Donaldson

ABSTRACT

The flow of xylem sap in bamboo is closely associated with metaxylem vessels and the pits in their cell walls. These pits are essential components of the watertransport system and are key intercellular pathways for transverse permeation of treatment agents related to utilization. Observations of metaxylem vessels and pits in moso bamboo culm internodes were carried out using environmental scanning electron microscopy (ESEM) to examine mature bamboo fractures and resin casts. The results showed that bordered pits were distributed in relation to adjacent cell types with most pits between vessels and parenchyma cells and few pits between vessels and fibers of the bundle sheath. The pit arrangement was mainly opposite to alternate with apertures ranging from oval, flattened elliptical, or slit-like to coalescent. The vertical dimensions of inner apertures and outer apertures of the pits were about 0.9-2.7 μm and 1.1-3.8 μm, respectively. According to the relative position, and size difference between the inner apertures and their borders, the bordered pit shapes were categorized into three types, namely PI, PII and PIII (Fig. 3C). Half-bordered pit pairs were observed between vessels and direct contact parenchyma cells. Most vessel elements possessed simple perforation plates.

Juan Guo, Lin Xiao, Liuyang Han, Hao Wu, Tao Yang, Shunqing Wu and Yafang Yin

Edited by Lloyd A. Donaldson

ABSTRACT

The relationship between the cell wall ultrastructure of waterlogged wooden archeological artifacts and the state of water bound to cell walls and free in voids is fundamental to develop consolidating and drying technologies. Herein, a lacquer-wooden ware and a boat-coffin dating 4th century BC were selected as representative artifacts to study. Wood anatomy results indicated that they belonged to Idesia sp. and Machilus sp., respectively. They exhibited a typical spongy texture, as revealed by SEM observations, and their water contents had increased significantly. Solid state NMR, Py-GC/MS, imaging FTIR microscopy and 2D-XRD results demonstrated that the deterioration resulted from the partial cleavages of both polysaccharide backbones and cellulose hydrogen-bonding networks, almost complete elimination of acetyl side chains of hemicellulose, the partial depletion of β-O-4 interlinks, as well as oxidation and demethylation/demethoxylation of lignin. These further caused the disoriented arrangement of crystalline cellulose, and the decrease in cellulose crystallite dimensions and crystallinity. In consequence, mesopores and macropores formed, and the number of moisture-adsorbed sites and their accessibility increased. Moreover, results on free water deduced by the changes of pore structure and the maximum monolayer water capacity achieved by the GAB model indicated that water in waterlogged archeological wooden artifacts was mainly free water in mesopores.

Editors IAWA List of Microscopic Bark Features

Patrik Ahvenainen

ABSTRACT

Many endangered tropical hardwoods are commonly used in electric guitars. In order to find alternative woods, the current electric guitar woods need to be studied and classified as most research in this field has focused on acoustic instruments. Classification was done based on luthier literature, woods used in commercially available electric guitars, commercially available tonewoods and by interviewing Finnish luthiers. Here, the electric guitar woods are divided into three distinct classes based on how they are used in the guitar: low-density wood used in the body only (alder, poplar, basswood, ash), medium-density wood used in the body and neck (maple and mahogany), and high-density wood used in the fretboard only (rosewood and ebony). Together, these three classes span a wide range of anatomical and mechanical properties, but each class itself is limited to a relatively narrow parameter space. Statistically significant differences between these classes and the average hardwoods exist in the wood anatomy (size and organization of vessels, fibres, rays and axial parenchyma), in the mechanical properties (density, elastic modulus, Janka hardness, etc.) and in the average price per volume. In order to find substitute woods for a certain guitar wood class, density and elastic modulus can already be used to rule out most wood species. Based on principal component analysis of the elastomechanical and anatomical properties of commercially available hardwoods, few species are similar to the low- and high-density class woods. However, for all of the three electric guitar wood classes, non-endangered wood species are already commercially available from tonewood retailers that match the class characteristics presented here.