Volume 76, Issue 7

The image information and spectral information of wood sections can be used to identify wood species. Hyperspectral images have both image information and spectral information, but they have disadvantages such as large data capacity, slow reading speed, and the necessity of expensive equipment for their acquisition. In this study, the classification results of Pterocarpus by using visible/near infrared (VIS/NIR) spectral information and RGB images were compared with hyperspectral images. The VIS/NIR spectral curves, Hyperspectral, and RGB images of five wood species of Pterocarpus with similar transverse-sections were collected. In feature-level fusion, the feature vectors are directly connected in series, and features fused by canonical correlation analysis are compared. In decision-level fusion, an extreme learning machine and a composite-kernel support vector machine (SVM) are used and compared. In the feature- and decision-level fusion methods, the recognition results of VIS/NIR spectral curves plus RGB images were largely similar to those of hyperspectral images. Therefore, a recognition effect similar to that of the hyperspectral image can be obtained by collecting the spectral information and image information of wood sections separately, which can reduce the cost of data acquisition and improve the speed of data processing.

Wood permeability is a macroscopic property resulting from complex pathways at the cellular level. In this study, high-resolution X-ray CT scans were performed during longitudinal imbibition in Norway spruce to investigate the role of wood rays and tracheids network in liquid migration. A customized setup was designed to maintain the bottom face of a wooden cylinder in contact with water, without vibration, despite the sample rotation required during each scan. The results highlighted a contrasted role of latewood and earlywood in water migration. Liquid imbibition was fast in latewood, because the bordered pits are less prone to aspiration than in earlywood, due to their smaller diameter and larger cell wall thickness. In earlywood, the migration pattern was complex due to pit aspiration that isolate tracheids clusters. Indeed, the images revealed a significant contribution of wood rays in the migration pathways. Consequently, tracheids were not progressively filled in the longitudinal direction from one tracheid to the next, but they were filled laterally with water coming from wood rays at different heights of the cells. This explained entrapped air bubbles in the lumens and led to a 3D heterogeneous liquid distribution.

Thioacidolysis is widely used for lignin structural characterization by cleaving β-aryl ethers to release syringyl (S), guaiacyl (G), and p -hydroxyphenyl (H) monomers followed by GC analysis. However, the traditional thioacidolysis method requires tedious extraction steps with chlorinated solvent underlying harmful to health, limiting its efficiency and application. Herein, an improved thioacidolysis method with high sensitivity for the quantitation of lignin-derived monomers was developed. The improved protocol used a quick, streamlined procedure to recover the monomeric products using ethyl acetate as extracting solvent and MS detector in multi-reaction monitoring mode to enhance its ability to detect extremely low concentration (0.1 ppb with signal-to-noise higher than 2) of monomeric products. Additionally, a fast GC program was established to speed up the GC quantitation. Several representative lignocellulose samples, including gymnosperm, angiosperm, and poaceae, were used to test this tailored method. The results demonstrated that the ratios of lignin monomer compositions determined by this method were consistent with that of traditional procedure despite the slightly higher monomer yields measured. More importantly, this method uses non-chlorinated solvent for microscale extraction and requires no evaporation step for workup, which is a green and efficient way for the quantification of lignin monomer compositions.

A new laboratory reactor to perform in situ studies of structural changes in wood during soda pulping using synchrotron X-ray tomography is presented. The reactor is of recirculation type to provide stable reaction conditions and mimic the industrial situation. Experiments have been performed using this reactor in situ at a synchrotron microtomography beamline to provide sequences of 3D images from which measurement of wood cell wall thickness have been possible for the first time. The results showed that the cell wall thickness increased significantly in the early stage of pulping (<10 min), which is due to the transportation of cooking chemicals through the tracheids, resin channels and pits into the cell wall, which is swollen with the increased pH. Subsequently, the cell wall thickness reduces over the processing time up to 60 min with a high rate, which is inferred to be due to the dissolution and transport of lignin and hemicellulose from the secondary walls, allowing for better transportation of active chemicals deep through the cell wall layers. After 60 min processing, the cell wall thickness reduction rate reduced, as dissolution of lignin and hemicelluloses from the cell walls ceased, while the remaining dissolution occurs mainly at the middle lamella.

Bacterial decay in compression wood (CW) tracheids of waterlogged archaeological wood (WAW) was investigated using light microscopy, confocal laser scanning microscopy, transmission electron microscopy (TEM), and TEM immunogold labeling. Erosion bacteria were identified as the main degraders, and the extent of cell wall degradation differed depending on the severity of CW tracheids (mild vs. severe). Mild CW tracheids showed preferential decay in the inner S 2 layer, with the locally degraded and/or fragmented S 3 layer remaining. In contrast, severe CW tracheids revealed gradual degradation of the cell wall from the erosion progressing from exposed faces of the cell wall as decay progressed. The overall decay was more extensive in mild than in severe CW tracheids, and degradation of the highly lignified outer S 2 layer (S 2L ) was only detected in mild CW tracheids. TEM immunogold labeling of 1,4- β -galactan, homogalacturonan (HG), heteroxylan, and heteromannan epitopes showed that there was no preferential degradation of pectins and hemicelluloses by action of diffusible enzymes and/or agents through the un-decayed cell wall during bacterial decay, in both mild and severe CW tracheids. Inter-CW tracheid bordered pit membranes showed higher decay resistance than CW tracheid walls. Degradation of HG and heteromannan epitopes was suppressed in pit membranes.

Heat-treated wood (HTW) has better dimensional stability but worse mechanical strength than untreated wood. This study aimed to overcome this shortcoming by sulfonating lignin in Balfour spruce ( Picea likiangensis var. balfouriana ) wood with sulfurous acid and Na 2 SO 3 followed by heat treatment. The mass loss of as-prepared HTW decreased while the crystallinity index increased slightly compared with those of HTW without sulfonation pretreatment. The cellulose structure of the as-prepared HTW was not damaged by the sulfonation pretreatment. The as-prepared HTW showed a higher MOE, MOR, and compressive strength (CS) of 34, 32, and 22%, respectively, compared with the HTW without sulfonation treatment. The improved mechanical properties were attributed to the increase of the relative mass fraction of lignin in the secondary walls of wood, as sulfonated lignin could migrate with water from the compound middle lamellae into the secondary wall under the combined driving forces of a concentration difference and steam pressure. These findings provide a way to enhance the mechanical properties of HTW while gaining better hydrophobicity.

In this study, Anatolian black pine ( Pinus nigra subsp. pallasiana ) was treated with fire retardants of 10, 20, and 30% aqueous solutions composed of di-ammonium phosphate (DAP), borax, boric acid, and glucose to determine the effectiveness of these chemicals in preventing the spread of fire. The treated wood was subjected to post-heat treatment at 120, 150, and 180 °C for 1 h to examine the effects of the post-heat treatment on pH changes, anti-swelling efficiency, water absorption, mechanical strength, accelerated weathering, leaching resistance, thermogravimetric analysis (TGA), UL-94 vertical burning test and crystallinity index. The post-heat treatment of fire-retardant treated wood reduced water intake and increased dimensional stability, while also improving mechanical and thermal properties in general. DAP/glucose complexes promote phosphorus fixation in wood and reduce leaching, resulting in long-term fire protection of wood in service. Because of these improvements in the post-heat treated wood by impregnated fire retardant, it can potentially be used as a reliable engineering material in a wide range of structural applications.

The revolutionary transformation of opaque wood into a transparent material, with combination of high optical transmittance and high haze, has gained widespread interest in the realms of advanced functional materials. However, the thickness of transparent wood composite (TWC) is limited to a few millimeters which restricts potential use. In this study, TWC were prepared using transverse sections of poplar ( Populus deltoides ) in thickness ranging from 1.5 to 15 mm by lignin modification bleaching followed by epoxy resin infiltration. The effects of bleaching duration as well as sample thickness on the optical properties of TWC were investigated. TWC was characterized using scanning electron microscopy and FTIR spectroscopy. The optical properties of TWC were measured using UV-VIS-NIR spectroscopy. The results indicated that light transmittance depended on severity of bleaching, lignin content and sample thickness.

Leaning stems of woody plants form reaction wood, in hardwood trees termed tension wood (TW). Typical TW fibers, gelatinous fibers (G-fibers), are characterized by an inner gelatinous cell wall layer (G-layer). Xyloglucan endotransglycosylases (XETs) was proposed as the essential enzyme in cell wall modifications in TW, by making xyloglucan (XG) cross-links between G- and S 2 -layers in G-fibers, and thus maintaining their contact. The determination of TW presence in a sample is of great importance for the forest products industry, biofuel production, and tree physiology studies. However, TW is not easy to detect visually. The colorimetric assay for XET activity determination as an indicator of TW presence in a sample was tested on powdered stem segments of juvenile Populus x euramericana trees exposed to severe long-term static bending. In parallel, histochemical and ultrastructural characterization of stem samples of bent and control trees was performed. The tested colorimetric assay for XET activity determination could be suggested as a useful and easily applicable tool for fast screening of powdered wood samples for the presence of TW.

During the process of searching for tyrosinase inhibitors from natural medicines, one new monoterpene rhamnoside ( 1 ) and 13 known compounds ( 2 – 14 ) were isolated from the ethanolic extract of Betula platyphylla barks by repeated column chromatography. These structures were identified by comprehensive spectroscopic data analysis such as high-resolution electrospray ionization mass spectra (HR-ESI-MS), nuclear magnetic resonance (NMR), optical rotatory dispersion (ORD) and acid hydrolysis. In vitro assay revealed that compounds 6 , 7 and 14 showed obvious inhibitory activity against tyrosinase.