Wood Fiber Cell Research Articles

Self‐Micropatterned Wood Hydrophone for Underwater Detection

AbstractA hydrophone is a core component of sonar and plays a significant role in underwater detection. High sensitivity and wide‐frequency responsiveness are crucial parameters for underwater mechanosensors. This study introduces an innovative wood‐based hydrophone for precise detection of water wave spectra and a wide range of underwater sounds. The wood hydrophone consists of a conductive wood electrode with deposited polypyrrole (PPy) microbranches (polypyrrole wood (PW)) and a cellulosic micropatterned anti‐swelling hydrogel (MPASH) serving as the dielectric layer. As pressure increases within the range of 6.4 Pa to 1.2 kPa, the densely distributed PPy microbranches within the wood fiber cell lumina contact with more tips of the self‐wrinkled micropatterns of MPASH. This interaction results in a four‐order‐of‐magnitude increase in capacitance, leading to an unprecedented sensitivity of 1153 kPa−1 toward microstresses. Due to the presence of multisized configurations in both PW and MPASH, the sensitivity of the wood hydrophone decreases gradually (268 kPa−1 up to 37 kPa). The receiving sensitivity of the wood hydrophone for acoustic waves is greater than ‐174 dB within the frequency range of 250–2300 Hz. This work presents a promising avenue for the development of underwater detection devices utilizing graded wood channels and micropatterned cellulosic hydrogels.

The formation of xylem tissues and secondary cell walls is diminished by severe and consecutive insect defoliation.

Insect defoliation causes unusual wood structures in forest trees. However, the characteristics of the unusual wood structure of hardwoods remain unclear. The aim of this study was to clarify the characteristics of the wood structure in trunks produced under severe insect defoliation in Betula maximowicziana trees. Samples from the trunks were taken from two sites (Naie and Furano) in central Hokkaido where insect defoliation by Caligula japonica occurred during 2006-2012. The cross-dating and microscopic observations with histochemical staining were done. White rings with thin-walled wood fibers and drastic reduction in annual ring width in the subsequent year were observed in both samples. From these results, the formation year of white rings were determined and severe defoliation was confirmed to trigger white ring formation. The characteristics may prove useful for the detection of the formation year of white rings. Then, we clarified the cell morphology of wood fibers in the white rings. Scanning electron microscopy and histochemical analyses indicated that the thickness of the S2 layer of wood fibers decreased, but xylan and lignin were still deposited in the cell walls of wood fibers in a white ring. However, the cell-wall thickness of wood fibers recovered after defoliation period. Our results suggest that B. maximowicziana would respond to a temporary lack of carbon due to insect defoliation by regulating the thickness of the wood-fiber S2 layer. For B. maximowicziana, insect defoliation during the late growing season has serious deleterious effects on wood formation and radial growth. This article is protected by copyright. All rights reserved.

Chromosome-scale genomes of commercial timber trees (Ochroma pyramidale, Mesua ferrea, and Tectona grandis)

Wood is the most important natural and endlessly renewable source of energy. Despite the ecological and economic importance of wood, many aspects of its formation have not yet been investigated. We performed chromosome-scale genome assemblies of three timber trees (Ochroma pyramidale, Mesua ferrea, and Tectona grandis) which exhibit different wood properties such as wood density, hardness, growth rate, and fiber cell wall thickness. The combination of 10X, stLFR, Hi-Fi sequencing and HiC data led us to assemble high-quality genomes evident by scaffold N50 length of 55.97 Mb (O. pyramidale), 22.37 Mb (M. ferrea) and 14.55 Mb (T. grandis) with >97% BUSCO completeness of the assemblies. A total of 35774, 24027, and 44813 protein-coding genes were identified in M. ferrea, T. grandis and O. pyramidale, respectively. The data generated in this study is anticipated to serve as a valuable genetic resource and will promote comparative genomic analyses, and it is of practical importance in gaining a further understanding of the wood properties in non-model woody species.

An Oxidative Enzyme Boosting Mechanical and Optical Performance of Densified Wood Films.

Nature has evolved elegant ways to alter the wood cell wall structure through carbohydrate-active enzymes, offering environmentally friendly solutions to tailor the microstructure of wood for high-performance materials. In this work, the cell wall structure of delignified wood is modified under mild reaction conditions using an oxidative enzyme, lytic polysaccharide monooxygenase (LPMO). LPMO oxidation results in nanofibrillation of cellulose microfibril bundles inside the wood cell wall, allowing densification of delignified wood under ambient conditions and low pressure into transparentanisotropic films. The enzymatic nanofibrillation facilitates microfibril fusion and enhances the adhesion between the adjacent wood fiber cells during densification process, thereby significantly improving the mechanical performance of the films in both longitudinal and transverse directions. These results improve the understanding of LPMO-induced microstructural changes in wood and offer an environmentally friendly alternative for harsh chemical treatments and energy-intensive densification processes thusrepresenting a significant advance in sustainable production of high-performance wood-derived materials.

Wood identification of Cyclobalanopsis (Endl.) Oerst based on microscopic features and CTGAN-enhanced explainable machine learning models.

Accurate and fast identification of wood at the species level is critical for protecting and conserving tree species resources. The current identification methods are inefficient, costly, and complex. A wood species identification model based on wood anatomy and using the Cyclobalanopsis genus wood cell geometric dataset was proposed. The model was enhanced by the CTGAN deep learning algorithm and used a simulated cell geometric feature dataset. The machine learning models BPNN and SVM were trained respectively for recognition of three Cyclobalanopsis species with simulated vessel cells and simulated wood fiber cells. The SVM model and BPNN model achieved recognition accuracy of 96.4% and 99.6%, respectively, on the real dataset, using the CTGAN-generated vessel dataset. The BPNN model and SVM model achieved recognition accuracy of 75.5% and 77.9% on real dataset, respectively, using the CTGAN-generated wood fiber dataset. The machine learning model trained based on the enhanced cell geometric feature data by CTGAN achieved good recognition of Cyclobalanopsis, with the SVM model having a higher prediction accuracy than BPNN. The machine learning models were interpreted based on LIME to explore how they identify tree species based on wood cell geometric features. This proposed model can be used for efficient and cost-effective identification of wood species in industrial applications.

High-Performance Lignocellulosic Self-Bonding Composites via Dialdehyde Modification and Water-Involved Low-Temperature Hot Pressing

Novel lignocellulosic self-bonding materials with high performance and low hygroscopicity are still in demand in the wood industry. We demonstrated a facile and efficient approach to prepare adhesive-free all-lignocellulosic composites with excellent performances via the dialdehyde modification replacing the conventional hydrogen groups. Less than 30% water involved as the plasticizer could successfully optimize the performances of self-bonding composites and, more importantly, realize low-temperature hot pressing at 75 °C. The internal sectional morphology showed that individual wood fiber cells collapsed, and lignin was repolymerized with hemicellulose and cellulose to enhance interfacial bonding. Chemical analysis demonstrated the intra- and intermolecular association of dialdehyde groups. The self-assembly lignocellulosic composites were superior to most of the reported adhesive-free bio-fiber materials, demonstrating better flexural strength (93.7 MPa), internal bond strength (6.2 MPa), tensile strength (20.2 MPa), and hardness (1.0 GPa). Thus, this technology can be extended to different wood species. The thickness swelling rate of lignocellulosic self-bonding composites was only 2.1% after soaking in water for 24 h. In addition, the adhesive-free lignocellulosic composites exhibited plastic body-like behavior and excellent machinability. The applications of all-lignocellulosic self-bonding composites can be extended to high-strength structural buildings and outdoor household material fields, which aligns with the concepts of eco-friendliness, degradation, and carbon storage.

Microscopic deformations in MDF swelling: a unique 4D-CT characterization

Medium-density fiberboard (MDF), a wood-based material that consists of a tight random network of wood fibers, deforms more than wood when exposed to water. For the first time, the microscopic deformations of MDF were tracked during swelling. A hygroscopic swelling setup imposing the material to deform throughout tomographic acquisition was used coupled to X-ray microtomography. An advanced reconstruction algorithm enabled reconstruction of images free of motion artefacts, and state-of-the-art digital volume correlation was applied to determine the mechanical strain fields at high resolution. Wood fiber bundles were then segmented from single fibers with deep learning using the UNet3D architecture. Combined with the strain fields, this segmentation showed that wood fiber bundles were the drivers of MDF swelling. This contrasts with the hygroscopic behavior of wood, where structured wood swells less than single fibers, which might be caused by a difference in penetration and distribution of the adhesive, in and on the wood fiber cell wall. The unique characterization of MDF’s dynamic behavior can already be used to develop manufacturing strategies to improve water resistance, therefore widening the uses of natural fiber-based materials.

Metabolome and transcriptome analyses identify the plant immunity systems that facilitate sesquiterpene and lignan biosynthesis in Syringa pinnatifolia Hemsl.

BackgroundSyringa pinnatifolia Hemsl. is a shrub belonging to the Oleaceae family. The peeled woody stems and roots of S. pinnatifolia are used in Chinese traditional medicine. This plant has been used for centuries, and modern pharmacological research has revealed its medicinal value. However, the wild populations of S. pinnatifolia have been decreasing, and it has been listed as an endangered plant in China. To elucidate the molecular mechanism leading to the synthesis of the major components of S. pinnatifolia for its further development and sustainable use, this study compared peeled stems and twigs at the metabolic and molecular levels.ResultsPeeled stems with the purple substance visible (SSP) and peeled twigs without the purple substance (TSP) were compared at different levels. Microscopic observation showed resin-like fillers in SSP and wood fiber cell walls approximately 1.0 μm thicker than those in TSP (wood fiber cell thickness approximately 2.7 μm). In addition, 104 volatile organic compounds and 870 non-volatile metabolites were detected in the non-targeted and widely-targeted metabolome analyses, respectively. Among the 76 differentially accumulated metabolites (DAMs) detected, 62 were up-accumulated in SSP. Most of these DAMs were terpenes, of which 90% were identified as sesquiterpenes in the volatile organic compound analysis. In the analysis of the non-volatile metabolites, 21 differentially accumulated lignans were identified, of which 18, including five subtypes, were accumulated in SSP. RNA sequencing revealed 4,421 upregulated differentially expressed genes (DEGs) and 5,522 downregulated DEGs in SSP compared with TSP, as well as 33,452 genes that were not differentially expressed. Analysis of the DEGs suggested that sesquiterpenes and lignans were mostly biosynthesized via the mevalonate and phenylpropanoid pathways, respectively. Additionally, in SSP, the enriched Gene Ontology terms included response to biotic stimulus and defense response, while the enriched Kyoto Encyclopedia of Genes and Genomes pathways included plant–pathogen interaction and many other pathways related to plant immunity.ConclusionsThis study provides metabolome and transcriptome information for S. pinnatifolia, suggesting that biotic stimuli, including pathogens, are potential and valuable approaches to promoting the biosynthesis of the metabolites linked to the medicinal properties of this plant.

Prior secondary cell wall formation is required for gelatinous layer deposition and posture control in gravi-stimulated aspen.

Cell walls, especially secondary cell walls (SCWs), maintain cell shape and reinforce wood, but their structure and shape can be altered in response to gravity. In hardwood trees, tension wood is formed along the upper side of a bending stem and contains wood fiber cells that have a gelatinous layer (G-layer) inside the SCW. In a previous study, we generated nst/snd quadruple-knockout aspens (Populus tremula × Populus tremuloides), in which SCW formation was impaired in 99% of the wood fiber cells. In the present study, we produced nst/snd triple-knockout aspens, in which a large number of wood fibers had thinner SCWs than the wild type (WT) and some had no SCW. Because SCW layers are always formed prior to G-layer deposition, the nst/snd mutants raise interesting questions of whether the mutants can form G-layers without SCW and whether they can control their postures in response to changes in gravitational direction. The nst/snd mutants and the WT plants showed growth eccentricity and vessel frequency reduction when grown on an incline, but the triple mutants recovered their upright growth only slightly, and the quadruple mutants were unable to maintain their postures. The mutants clearly showed that the G-layers were formed in SCW-containing wood fibers but not in those lacking the SCW. Our results indicate that SCWs are essential for G-layer formation and posture control. Furthermore, each wood fiber cell may be able to recognize its cell wall developmental stage to initiate the formation of the G-layer as a response to gravistimulation.

Study on the ultrastructure and properties of gelatinous layer in poplar

As a fast-growing commercial wood species, poplar often produces tension wood because of the leaning stems of logs, which has a great impact on the production and utilization. The gelatinous layer (G-layer) was the unique component of tension wood, almost entirely composed of cellulose, which was the main reason for the special performance of the poplar tension wood. This study used the transmission electron microscopy, Raman spectroscopy and nanoindentation to examine the ultrastructure and mechanical properties of every wall layer of the poplar cell wall in order to figure out the ultrastructure and properties of G-layer. In particular, the nanoindentation mapping was combined with manual screening to obtain the mechanical performance data of each layer. The fibers in the tension wood were gelatinous wood fibers with obvious G-layers, and the thickness was 2.53 μm, which was much larger than that of other wall layers. Compared with the wood fiber in the opposite wood, the S1 layer was thicker and the S2 layer was thinner, and the entire cell wall thickness was increased in tension wood. G-layer in tension wood had a very high cellulose content, and the Raman strength of lignin was weak. In general, the micromechanical properties of poplar tension wood were better, which was consistent with its macromechanical properties. The characteristics of G-layer, including high cellulose content, small microfibril angle and high crystallinity, made G-layer own better elastic modulus (14.08 GPa) and hardness (0.45 GPa) than other wall layers in the tension wood. Moreover, G-layer had a high proportion in the tension wood cell wall, so the average longitudinal elastic modulus and hardness of wood fiber cells in the tension wood were also higher than those in the opposite wood.

PtiCYP85A3, a BR C-6 Oxidase Gene, Plays a Critical Role in Brassinosteroid-Mediated Tension Wood Formation in Poplar.

In angiosperm trees, the gelatinous layer (G-layer) takes a great part of the fiber cell wall in the tension wood (TW). However, the mechanism underlying G-layer formation in poplar is largely unknown. In this work, we demonstrate that G-layer formation in poplar TW cells is regulated by brassinosteroid (BR) and its signaling. PtiCYP85A3, a key BR biosynthesis gene, was predominantly expressed in the xylem of TW, accompanied with a relatively higher castasterone (CS) accumulation, than in the xylem of opposite wood (OW). A wider expression zone of BZR1, a key transcriptional factor in BR singling pathway, was also observed in G-fiber cells on TW side than in wood fiber cells on the OW side, as indicated by immunohistochemistry assays. Transgenic poplar plants overexpressing PtiCYP85A3 produced thicker G-layer with higher cellulose proportion, and accumulated more BZR1 protein in the xylem of TW than did the wild type (WT) plants. Expression of most TW-associated CesAs, which were induced by 2, 4-epibrassinolide, an active BR, and inhibited by brassinazole, a BR biosynthesis inhibitor, were also up-regulated in the xylem of TW in transgenic plants compared to that in WT plants. Further studies with dual-luciferase assays demonstrated that the promoters of PtiCesAs were activated by PtiMYB128, a TW specific transcription factor, which was then regulated by BZR1. All these results indicate that BR plays a crucial role in the G-layer formation of TW fiber cells by regulating the expression of BZR1, PtiMYB128, and PtiCesAs in poplar.

Effects of wood rays on the shrinkage of wood during the drying process

To elucidate the origin of shrinkage anisotropy of wood during the drying process, wood from three tree species, Quercus sp., Juglans nigra, and Pometia pinnata, was analyzed using thin cryomicrotome sections and sequential drying on a micro-scale. The data on shrinkage, based on the transverse direction, were calculated using Image Pro Plus software to measure the thickness of the cell wall of fibers. The results showed that: (1) In the tangential direction, the shrinkage of wood fibers were all in the “smallest-bigger-smaller (-bigger-smaller)” pattern from A to C (A: The cells closest to the wood rays; C: The cells in the middle between the wood rays) and fibers next to the rays always have the minimum shrinkage at different moisture contents; (2) the width of the rays has no negative correlation with the shrinkage of wood fibers; and (3) the rays have the same effect on the shrinkage of wood fiber cells in both latewood and earlywood. In addition, the shrinkage of latewood is more severe than that of earlywood, which leads to tangential shrinkage.

Transition characteristics of a carbonized wood cell wall investigated by scanning thermal microscopy (SThM)

The transition characteristics of Quercus rubra wood fiber cell walls during carbonization were investigated by means of scanning thermal microscopy (SThM). Wood samples were carbonized at temperatures from 200 to 600 °C. SThM investigations indicated that the secondary wall (S2) and compound middle lamella (CML) of the wooden fiber cell wall (FCW) could easily be distinguished in the cross section because of the difference in thermal conductivity between them, but when the carbonization temperature was increased, the difference decreased and disappeared at carbonization temperatures above 325 °C. Confocal Raman microscopy studies indicated that the concentrations of cellulose and lignin differed significantly in the S2 and CML, and when carbonized at temperatures higher than 325 °C, the chemical component of the FCW became homogenous. The changes of the dimensions of FCW were also investigated. The FCW became noticeably thinner during carbonization. Compared to native wood, the thickness decreased by 62% when carbonized at 600 °C and the loss of thickness occurred simultaneously with weight loss. The key temperature was 300 °C, with most shrinkage and weight loss occurring before 300 °C.

Constructing 3D Model of Hardwood Structure

Model constructing was conducted with 3D Studio Max modeling technology for hardwood minute structure in three steps. In the first step, the single-cell models were built according to the true form and shape of various kinds of cells, including vessel elements, wood-fiber cells, longitudinal parenchyma cells and ray cells. In the second step, the single-tissue models for all the four kinds of wood tissues (vessel, wood-fiber, longitudinal parenchyma and wood ray) were constructed by setting the same kind of single-cell models together according to the cell grouping ways inside true wood. In the third step, according to the distributing and arranging ways of the four kinds of wood tissues inside true wood, the whole model of wood block in minute structure was constructed by assembling the four kind of single-tissue models in a block. After that, the virtual model in computer was materialized by means of modern 3D printing technology, and finally the solid model in minute structure of Ficus microcarpa wood was constructed.

Virtual characterization of MDF fiber network

A virtual design method for medium density fiberboards (MDF) is proposed with the aim to optimize the fiber orientation and lay-up of MDF. The new method estimates the stiffness and strength by using microstructure models of the MDF fiber network. The virtual design is used to improve the manufacturing technology of MDF plates with multilayer oriented fiber structure. Experimental investigations of the mechanical behavior of MDF microstructure for various fiber geometries, glue content and distribution are complicated, time consuming and expensive. On the other side, virtual microstructure design allows to develop a new wood fiber based material with less experimental work. Microstructure models help to better understand the non-linear damage mechanical behavior of a wood fiber network depending on fiber geometrical parameters. Such parameters as crack distribution and fiber deformation on micro-scale level are complicated to experimentally measure, but possible to model using computer simulations. The virtual design tool requires less empirical data. The model takes into account information on average wood fiber orientation, fiber diameter, fiber length and mechanical properties of wood fiber cell wall and glue. The numerical method for strength and stiffness analysis of MDF microstructure was calibrated using standard MDF with non-oriented fibers. It turned out that this method gives precise results for MDF with oriented fibers and even with multilayer structure. The proposed virtual microstructure design tool can significantly improve and speed-up the optimization manufacturing technology of MDF and other wood fiber based composites.

Contributions of Basic Chemical Components to the Mechanical Behavior of Wood Fiber Cell Walls as Evaluated by Nanoindentation

Selective chemical extraction was applied to gradually remove classes of chemical components from wood cell walls. Nanoindentation was performed on the control and treated wood cell walls to evaluate the contributions of the chemical components to the cell walls by measuring the elastic modulus, hardness, and creep compliance. Burger’s model was applied to simulate the process of nanoindentation and to gain insight into the response of visco-elastic properties to the chemical components. Wood extractives showed limited effects on the cell-wall mechanics; however, the removal of hemicelluloses and lignin resulted in reductions of 11.7% and 28.4%, respectively, in the elastic modulus and 14.8% and 30.4%, respectively, in the hardness. The extraction of hemicelluloses and lignin reduced the resistance of wood cell walls to creep. Furthermore, the extracted parameters from Burger’s modeling indicated that cellulose exhibited the greatest influence on the mechanical properties of wood cell wall, while hemicelluloses exhibited the greatest contribution to cell-wall viscosity, and lignin contributed extensively to cell-wall elasticity.

Recycled HDPE reinforced with sol–gel silica modified wood sawdust

The goal of the work was improvement of mechanical and tribological properties of high density polyethylene (HDPE) while finding use for wood sawdust (wood flour). Two chemical modification methods have been used for wood sawdust treatment to improve compatibility between the HDPE matrix and wood sawdust. Traditional silane coupling was used as a first approach to modify the sawdust by 3-methacryloxypropyl-trimethoxysilane (3MPS) and thereby forming COSi bonds. As a second method, we decided to combine sol–gel process with 3MPS treatment to form SiOSi and COSi linkages. Silica nanoparticles are filling wood fiber cells and silica rods formation is seen; as a result, thermal expansivity decreases. As expected, the enthalpy of fusion and the degree of crystallinity go down with increasing filler concentration. Tensile modulus goes up as result of filler loading while the tensile strain at break goes down. As the result, brittleness B goes up somewhat, but overall the values of B are quite low. With one exception, residual depth in scratch resistance testing decreases as a consequence of introduction of the fillers. Addition of unmodified wood results in increasing dynamic friction, chemical modification of wood particles results in lowering friction. Combination of focused ion beam milling with scanning electron microscopy shows clearly positive effects of modification on adhesion between the phases.

Wood Density of Ten Native Trees and Shrubs and Its Possible Relation with a Few Wood Chemical Compositions

The present study was undertaken in Forest Science Faculty, Universidad de Nuevo Leon, Mexico on variability of Wood density and its possible relation to few wood chemical composition and wood fiber cell structure anatomy. The results reveal that among 10 specie studied, there exist a large variation in wood density (0.51 to 1.09), and few wood chemical composition such % carbon (37.14 to 44.07), nitrogen (9.18 to 19.22), sulphur (31.45 to 33/82), lignin (15/28 to 24.35), hemicellulose (19.94 to 27.36%), and % cellulose (33.69 to 45.92). In general, though there was no clear relationship between wood density and other chemical composition of wood. It was observed that the species having moderate to high wood density contained >40% carbon, >30% sulphur and >40% cellulose and more or less 20% lignin. It seems that carbon, sulphur, cellulose and lignin content contribute to greater density. The wood fiber cell with wall lignification seems to be related to higher wood density.

Poplar wood–methylol urea composites prepared by in situ polymerization. II. Characterization of the mechanism of wood modification by methylol urea

ABSTRACTA prepolymer was used to prepare wood/prepolymer composites by a pulse‐dipping machine. The mechanical properties and dimensional stability were evaluated. The characterization of natural and modified woods was performed by Fourier transform infrared spectroscopy, 13C‐NMR spectroscopy, X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) with energy‐dispersive X‐ray analysis (EDXA). Cross‐polarization/magic‐angle spinning 13C‐NMR analysis revealed that the in situ polymerization between the prepolymer and the hydroxyls in the wood structure took place with the reduction of hydroxyl groups. XPS analysis indicated that the content of carbon decreased, whereas the content of oxygen increased. SEM–EDXA indicated a good dispersion of the modifier in the wood fiber and other vertical cells. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42406.

Numerical prediction of the stiffness and strength of medium density fiberboards

A numerical two scale method for the prediction of tensile and bending stiffness and strength of medium density fiberboards (MDF) is proposed with the aim to study the fiber orientation influence on mechanical properties of MDF. The method requires less experimental data to optimize MDF and to improve industrial manufacturing technology of MDF. A new method for computing orientation tensors of the compressed fiber network is proposed. First, the virtual microstructure is generated by simulations of a fiber lay-down and a subsequent compression to obtain the necessary density. The density profile, fiber length, thickness, and orientation are used for the microstructure generation, which are obtained from μCT images and image analysis tools. Then a new damage model for the wood fiber cell walls and joints is introduced. The microstructural problem is formulated as a Lippmann–Schwinger type equation in elasticity and solved by using Fast Fourier Transformation (FFT). The macroscopic three point bending test is simulated with hexahedral finite elements and analytical methods based on Euler–Bernoulli theory. The difference between bending strength and stiffness numerically obtained and corresponding experimentally measured values is less than 10%. This study lays a foundation for the optimal design of MDF fiber structures and the optimization of industrial manufacturing processes. The first results show an increase of up to 60% for bending stiffness in the case of strongly oriented fibers.