The WUSCHEL (WUS) transcription factor is the central organizer of shoot apical meristem (SAM) stem cells, yet its functions in woody plants remain poorly understood. This review synthesizes current knowledge of WUS and WUS-related homeobox (WOX) family genes in forest trees, spanning evolutionary genomics, vascular cambium regulation, somatic embryogenesis(SE), hormonal and environmental signal integration, and biotechnological applications. Comparative genomic analyses reveal "transitional" WUS genes in gymnosperms, illuminating the evolutionary trajectory from ancient to modern meristem regulation. In the vascular cambium unique to woody plants, WOX4 maintains cambial cell identity and prevents ectopic xylem differentiation, while contrasting CLAVATA3/EMBRYO SURROUNDING REGION-related(CLE) peptide pathways-the CLAVATA3(CLV3)-WUS negative feedback in the SAM versus the TDIF-PXY-WOX4 positive axis in the cambium-highlight WUS/WOX functional diversification across meristems. We discuss how WUS and derived functional peptides overcome regeneration recalcitrance, a major bottleneck in forest tree genetic transformation, and examine how cytokinin(CK)-auxin cross-talk, light, nutrient, and abiotic stress signals modulate WUS/WOX expression. Finally, we outline strategies for deploying CRISPR-based WUS regulation to improve wood properties, plant architecture, and stress resilience in forest trees. This integrative perspective positions the WUS/WOX family as a central nexus linking stem cell biology, environmental adaptation, and applied tree breeding.

Catalpa bungei is a valuable timber species famous for its high-quality wood properties, which are greatly compromised by tension wood (TW) formation. However, the molecular mechanisms underlying TW remain unclear. In this study, we identified thatCbuMYB27 was specifically upregulated during TW formation in C. bungei. CbuMYB27 exhibits thehighest expression level in the stem and its encoded protein possesses transcriptional activation activity. Overexpression of CbuMYB27 in hybrid poplar (84K) resulted in increased cambium layers and xylem width. Further analysis revealed that CbuMYB27 negatively regulates lignin biosynthesis. Molecular analysis indicated that CbuMYB27 positively regulates cambial activity and negatively regulates lignin biosynthesis by directly activating cambium-related genes and suppressing lignin-biosynthetic genes, respectively. Protein interaction assays indicated that CbuMYB27 physically interacts with a bHLH transcription factor, CbuBIM1. Although CbuBIM1 cannot directly regulate the target genes of CbuMYB27, it antagonizes CbuMYB27-mediated transcriptional regulation of these downstream genes. Moreover, CbuBIM1 attenuates the promoting effect of CbuMYB27 in TW formation caused by bending stress. In summary, our findings identify a functionally antagonistic module of CbuMYB27- CbuBIM1, which is involved in TW formation by modulating cambium activity and lignin biosynthesis in C. bungei and thus provides a potential target for the improvement of wood quality in C. bungei.

Fast-growing wood species are often characterized by low density, unsatisfactory mechanical properties, and poor biological durability. Therefore, various modification techniques have been tested to improve these disadvantages. The aim of this research work was to investigate the effects of densification of Salix alba (white willow) under hot pressing for 15 and 30 minutes on its physical and mechanical properties. Vapor pre-treatment for four and six hours was also applied to mitigate the negative effects of cracks and checks caused by breakage in wood cell wall under pressure. Markedly, separate sets of specimens were impregnated with aluminum oxide nano-suspension to evaluate if an increase in thermal conductivity would improve the properties of wood. The results indicated that densification significantly enhanced both the physical and mechanical properties of the wood. The four-hour vapor pre-treatment demonstrated the optimal improving results in both hot pressing durations. Though impregnation of specimens with the nano-suspension improved some properties (including spring back, hardness, and physical properties), most of the studied mechanical properties did not show any statistically significant improvement. Therefore, it was concluded that densifying willow wood for 15 minutes with a four-hour vapor pre-treatment yields optimal results. The enhancement in mechanical properties due to nano-aluminum oxide was not substantial enough to justify the associated costs, and thus, its use is not recommended for industrial applications.

ABSTRACT The growth process shapes the structure of trees in forest, and the rate the stems thicken over time is linked with wood properties such as ring width and wood density. This study investigated the potential of bi-temporal terrestrial laser scanning (TLS) for measuring the secondary growth of coniferous trees and assessing wood properties derived from core samples using X-ray microdensitometry over a nine-year period in boreal forests. TLS-derived DBH measurements demonstrated high agreement with reference data (r > 0.96). Volumetric secondary growth ( Δ v ) slightly outperformed basal area increment ( Δ g ) in capturing secondary growth dynamics as moderate correlations were found between TLS-derived estimates and mean ring width (RWm; r = 0.60–0.67). In contrast, correlations with ring basal-area-weighted wood density (WDg) were weak but statistically significant (r = –0.16 to –0.18) for both TLS and core-sampled measurements. The findings suggest that TLS can be used to measure secondary growth, but the ability to predict wood density of coniferous species via secondary growth measurements – neither with TLS nor core-sampling – is limited due to internal anatomical factors not captured by external measurements. Overall, these findings support the integration of TLS into forest monitoring frameworks, as it provides equally reliable yet more versatile data than callipers for measuring secondary growth.

Secondary cell wall (SCW) formation and lignin biosynthesis are critical biological processes that determine wood properties. Masson pine (Pinus massoniana Lamb) is a fast-growing conifer species with significant economic value for the pulp and paper industry. While R2R3-MYB transcription factors are known as master regulators of SCW biosynthesis, the specific R2R3-MYB members regulating lignin formation in Masson pine remain largely uncharacterized. In this study, we identified 317 R2R3-MYB genes in the Masson pine genome. Phylogenetic analysis revealed that PmMYB289, a member of the P20 subgroup, is highly homologous to the Arabidopsis SCW regulators AtMYB52 and AtMYB54. Expression profiling demonstrated that PmMYB289 is predominantly expressed in highly lignified old stems. Transcriptional activation assays confirmed that PmMYB289 lacks autoactivation activity. Subcellular localization analysis revealed that PmMYB289 was localized to the nucleus. Ectopic overexpression of PmMYB289 in tobacco (Nicotiana benthamiana) resulted in dwarfed plant growth, reduced stem diameter, and curled leaves. Molecular analysis of these transgenic lines showed a significant downregulation of most key SCW biosynthetic genes, with the exception of NbPAL1. These findings indicate that PmMYB289 acts as a crucial transcriptional repressor in SCW biosynthesis, providing valuable genetic resources for the molecular breeding of superior Masson pine varieties.

Super retarding-flame wood.

Properties of Eucalyptus clonal wood from a tropical region for application in civil construction

The demand for teak wood (Tectona grandis) as a wood construction and furniture material continues to increase, while available teak wood supplies remain limited and insufficient to meet market needs. One strategy to address this challenge is the development of clonal teak plantations using shoot cuttings and coppice teak. Both planting systems have the potential to enhance teak plantation productivity, although differences in growth performance, wood quality, and financial returns may occur. This study aimed to observe and compare growth characteristics, wood properties, and financial feasibility of clonal teak plantations established using shoot cuttings and coppice teak in two compartments in Perhutani Forest Management Unit (FMU) Ngawi, East Java, Indonesia. The research was conducted in Compartments 61 A and 59B, Sidolaju Forest Resort (RPH), Kedunggalar Forest Management Sub-unit (BKPH), Ngawi Forest Management Unit (KPH), Perhutani East Java Regional Division, Indonesia. Growth parameters measured included diameter at breast height (D), total tree height (H), tree bole height (TBH), crown width (CW), and stand volume (Volume). Wood quality was assessed using nondestructive methods, namely pilodyn penetration (P) and stress wave velocity (SWV). Furthermore, the financial performance of the clonal teak plantations included positive net present value (NPV), internal rate of return (IRR), and benefit–cost ratio (BCR) for shoot cutting and coppice teak plantations. The results indicated that the planting system significantly affected H, CW, P, and SWV, but it had no significant influence on D, TBH, and stand volume. At 11 years after planting, the total standing volume of clonal teak plantations established using shoot cuttings and coppice reached 175.5 ± 4.1 m³/ha, and 157.9 ± 7.1 m³/ha, respectively. Financial analysis showed positive NPV, IRR, and BCR for both systems, with no significant differences between them. These findings suggest that both shoot cutting and coppice are suitable for large-scale clonal teak plantations, as they produce comparable wood volume and quality while offering strong economic prospects.

The thermal modification alters the physical-chemical and mechanical properties of wood, potentially increasing its natural durability. Based on this, the objective of this study was to analyze the effects of thermal modification on wood from Eucalyptus grandis W. Hill ex Maiden × Eucalyptus urophylla S. T. Blake clones and its impact on chemical properties and biological resistance against drywood and subterranean termites. Wood samples from each clone were subjected to a heating ramp up to 185 and 200 °C. Chemically, the ash content (%) and total extractives (%) were analyzed. Biological resistance was assessed through choice feeding and no-choice feeding tests with drywood and subterranean termites. The parameters evaluated included mass loss, wood damage, number of holes (drywood termites), and termite mortality (no-choice feeding). After thermal modification, a decrease in total extractive content was observed. As for ash content, clone C showed an increase, while clone E presented a reduction. In the choice feeding tests with both termite groups, the samples thermally modified at 185 °C were the most consumed. In the no-choice feeding tests with drywood termites, clone C showed lower mass loss and fewer holes compared to clones A and E. It was concluded that thermal modification at the tested temperatures (185 and 200 °C) made the wood of E. grandis × E. urophylla clones more susceptible to attack by drywood and subterranean termites.

Thermal modification alters wood properties and helps improving dimensional stability against humidity changes, making it a promising treatment for wood used in stringed instrument construction. Its effects on the anisotropic mechanical and acoustical properties, however, remain incompletely understood. In this study, spruce samples were analyzed to quantify changes in physical, mechanical, and acoustical properties following thermal modification at 160 °C. Density, orthotropic viscoelastic constants, and damping were measured using non-destructive techniques, while microstructural effects were examined via x-ray microtomography. Finite element analysis of a guitar soundboard assessed impacts on eigenfrequencies, mode shapes, and acoustic radiation. Results indicate that thermal treatment causes a slight reduction in density, a modest increase in longitudinal and radial stiffness, and a significant decrease in damping, leading to enhanced radiation ratio and acoustic conversion efficiency. Microstructural observations suggest that removal of resins and volatile extractives may underlie these changes. Finite element analysis shows that eigenmodes shape remain largely unchanged, with only minor shifts in eigenfrequencies. The combination of improved radiation efficiency and reduced damping could influence sound radiation and string-to-soundboard coupling.

The genus Eucalyptus is of great economic importance for the Brazilian forestry sector and has been planted in various regions of Brazil, where the pulp and paper industry are the largest consumer of timber. The genus Eucalyptus is also recognized for its regrowth capacity, which is one of the factors contributing to its large-scale planting. Despite numerous studies on the regrowth quality of this genus, little is known about the quality and technological properties of regrowth wood, such as that of second-rotation trees, particularly for industrial use. Thus, the goal of this study is to evaluate the wood quality of second-rotation trees of two clonal hybrids of Eucalyptus urophylla S.T. Blake, aiming at their use in the production of pulp and paper. Two clonal hybrids of Eucalyptus urophylla S.T. Blake, approximately five years old, were used. To characterize wood quality, basic density, fiber dimensions, and wood quality indices for pulp and paper production were determined, including the Runkel ratio, wall proportion, Luce’s shape factor, stiffness coefficient, and flexibility coefficient. The wood from the first and second rotations showed similar patterns, especially in Clone 1. The results indicate that the second-rotation wood has the quality required for pulp and paper production.

The present study investigates simple cubic lattice structures fabricated through an FDM-based three-dimensional (3D) printing method using wood–polylactic acid (wood–PLA) bio-composite filament and develops a data-driven framework to predict their mechanical response. The design of experiments (DOE) was developed using a response surface methodology (RSM) based on a central composite design (CCD) that was implemented in Design-Expert software (Version 13). During fabrication, four different manufacturing parameters—the layer height, the printing speed, the nozzle temperature, and the infill density—were considered. The compressive strength and compressive modulus were evaluated experimentally, and the corresponding stress–strain responses were examined. The results reveal that the layer height is the most influential parameter, where lower layer heights (0.06–0.1 mm) significantly improve both the compressive strength and the modulus due to enhanced interlayer bonding and reduced void formation. The printing speed and the nozzle temperature also play critical roles, where lower printing speeds (≈40 mm/s) and moderate nozzle temperatures (≈195–205 °C) promote more uniform material deposition and improved interlayer bonding, while higher speeds (≥60 mm/s) and excessive temperatures (≈225 °C) lead to reduced bonding quality and a deterioration in mechanical performance. In contrast, the infill density exhibited a non-monotonic influence, where intermediate levels (around 70%) provided an improved performance under combinations of the low layer height (≈0.1 mm), the low printing speed (≈40 mm/s), and the moderate nozzle temperature (≈195–215 °C), suggesting an interaction-driven effect rather than a purely density-dependent trend. To complement the experimental findings, a machine learning model based on eXtreme Gradient Boosting (XGBoost) was developed using 12,000 data points that were derived from stress–strain curves. The model successfully predicted continuous mechanical responses with errors in the range of 2–8% for unseen specimens, suggesting its capability to capture the relationship between printing parameters and mechanical behavior within the studied design space. Overall, the study highlights that the mechanical properties of wood–PLA lattice structures can be effectively tailored by choosing an appropriate printing parameter control and demonstrates the feasibility of using machine learning to estimate mechanical performance without additional physical testing within the defined parameter domain.

ABSTRACT Growing environmental concerns over synthetic porous polymers have intensified the search for green and renewable natural substrates. Paulownia wood is a promising candidate due to its renewability, inherent porosity, and low density; however, its native lignin limits some high-value applications. Using an orthogonal experimental design, this study quantified the effects of five delignification variables on the chemical composition and physical properties of paulownia wood, aiming to optimize precursors for transparent, ultrastrong, and Highly hygroscopic wood. Delignification triggered competitive degradation: lignin removal was primarily governed by NaClO₂ concentration, while cellulose content was most sensitive to treatment time. The optimized process yielded tailored properties for three target materials. First, for the transparent wood precursor, the treatment significantly increased brightness while allowing for precise color adjustment. Second, substrate for ultrastrong wood was achieved through moderate delignification, which preserved the mechanical integrity of the cellulose scaffold. Third, Highly hygroscopic wood resulted from intensive delignification, leading to a substantial increase in water uptake and surface hydrophilicity. This work establishes quantitative structure–property relationships between delignification parameters and performance, offering theoretical and practical pathways for converting paulownia into high-value functional materials.

Ginkgo biloba is a valuable timber tree species, particularly suitable for high-end furniture manufacturing. Understanding the variations in its wood properties and their relationship with environmental factors is crucial for the selection and cultivation of superior timber germplasm. In this study, the analysis of 13 wood property indicators from 289 Ginkgo biloba across 20 regions revealed a relatively high variation coefficient (7.076% to 37.719%). With the exception of hemicellulose content, significant differences in other properties were observed among various regions. Correlation analysis demonstrated relationships among multiple traits, particularly indicating that an increase in tracheid wall thickness and the width-to-lumen ratio, along with a decrease in tracheid lumen diameter, could result in higher wood density. The ginkgo wood properties across multiple regions were assessed using principal component analysis and membership function method. The HC and LA regions were identified as sources of high-quality ginkgo wood, and several exceptional individual trees suitable for high-end furniture manufacturing were selected. Further investigation into the influence of environmental factors on ginkgo wood properties revealed that temperature, precipitation, and their fluctuations significantly affect wood density, tracheid morphology, and chemical composition. Regions with higher temperatures and precipitation, along with smaller fluctuations, exhibit greater wood density and larger tracheid, making them more suitable for furniture manufacturing.

Abstract Transparent wood is a promising sustainable alternative to glass, yet its large-scale production is often constrained by harsh chemical delignification, poor polymer compatibility, and limited interfacial control. This study introduces a solvent-free strategy for enhancing the optical and mechanical properties of transparent balsa wood through volumetric plasma modification using Atmospheric Discharge with Runaway Electrons (ADRE). The plasma treatment generates fast electrons capable of activating the entire wood volume, forming oxygen-containing functional groups that improve surface energy and polymer affinity. Morphological analyses (optical microscopy and SEM) revealed that plasma-treated samples exhibit homogeneous resin infiltration and the elimination of interfacial voids observed in untreated transparent wood. FTIR spectra confirmed the introduction of polar carbonyl and hydroxy groups, indicating enhanced chemical interaction between cellulose and the acrylic matrix. Consequently, the plasma-treated transparent wood achieved a visible light transmittance of 91% at 550 nm and reduced haze by 11% compared to non-treated samples. Mechanically, the plasma-treated transparent wood exhibited the highest bending strength in three-point bending tests (89.6 MPa), outperforming non-treated transparent wood (84.5 MPa) and raw wood (41.4 MPa), while partially modified wood showed the lowest strength. Hardness also increased from 83.3 to 86.7 Shore D after plasma activation, corroborating the improved interfacial adhesion and structural integrity. This solvent-free plasma activation approach replicates the interfacial benefits of chemical acetylation without toxic reagents or lengthy processing, providing a scalable and environmentally benign route toward high-performance, optically clear, and mechanically robust cellulose-based composites.

The transition from pure to mixed-species forest stands is increasingly promoted to enhance ecosystem stability and multifunctionality. The growth conditions may influence the physical and mechanical properties of wood. This study evaluated wood density in pure and mixed stands of silver birch, Norway spruce, and Scots pine in Lithuania and analyzed its relationships with tree allometric parameters. Nine study plots representing pure (100%) and mixed (70/30%) stands were established under comparable site conditions. Wood density at breast height was assessed using resistance drilling (IML Resi PD500), and the increment core samples were analyzed with the LIGNOSTATION™ system. The mean values of wood density for silver birch differed by 11%, depending on the wood density determination method used. Differences between pure and mixed stands were insignificant and generally did not exceed 6%–10%. No consistent trend that was attributable to species mixing was identified. The combined data from pure and mixed stands indicate that the mean wood density, converted from microdrilling measurements, was highest in silver birch (546 kg m−3 ± 1.87 kg m−3), followed by Scots pine (476 kg m−3 ± 1.85 kg m−3) and Norway spruce (437 kg m−3 ± 1.66 kg m−3). Resistance drilling showed a moderate relationship with the core samples’ wood density (R2 = 0.59), supporting its suitability as a semi-nondestructive method. Diameter at breast height was the only tree parameter that was consistently significant across all predictive models. The combined model for all species explained up to 43% of wood density variation, while species-specific models had lower explanatory power. Overall, the results indicate that species mixing has a limited effect on wood density under the studied conditions and is unlikely to substantially alter wood quality in terms of wood density.

Abstract Key message Using laser scanning and industrial data, we found that over 70% of wood quality variability occurred within Norway spruce ( Picea abies H. Karst) trees. The most important wood quality predictors were stem size, crown vigor, and growth rate inferred from laser scans. Random Forest models based on the laser-scanned features captured 25% of the industrially measured wood quality variability with 39.9% RMSE on average. The low crown plasticity of Norway spruce introduced biological constraints to laser scanning-based wood quality modeling. Context Wood quality models that also predict wood and timber properties in addition to size and growth variables are essential for increasing the precision of forest management and forest use, yet they remain notoriously untransferable. Laser scanning offers a powerful tool for their parameterization, but its ability to capture the within-tree variability of wood quality is still poorly understood in many species. Aims Our aim was to test whether multi-viewpoint laser scanning can capture within-tree gradients of wood quality in Norway spruce trees ( Picea abies H. Karst.), thereby enabling more robust and transferable models. Methods We analyzed 479 mature Norway spruce trees, combining handheld and airborne laser scanning with industrial wood quality data. We modeled 18 industrially relevant variables related to log geometry, heartwood, knottiness, and timber strength IP value against laser-scanned features at stand, tree, and log levels. Results Most wood quality variability (73%) occurred within trees. Log-level laser features explained 25% of the variation across stands and log types in the test data, with average RMSEs of 39.9%. The most stable predictions were obtained for heartwood ring width, heartwood density, and knot percentage. Conclusion Overall, external crown and stem attributes captured key growth responses but failed to robustly represent most wood quality factors in Norway spruce. These results underscore biological constraints in laser scanning-based wood quality modeling depending on the species-specific adaptiveness of the crown structure to the environment.

ABSTRACT Shrinkage induced defects in conventional drying severely restrict the applicability of plantation-grown eucalyptus wood, whereas steaming treatment (ST) can modify wood properties and drying characteristics to reduce or eliminate this issue. In this study, Eucalyptus urophylla × E. grandis was subjected to ST at 80 °C and 100 °C for 3, 6, and 9 hours, with effects on moisture content (MC), dimensional stability, drying kinetics, water uptake, and hygroscopicity systematically assessed. Results showed ST enhanced wood drying efficiency by accelerating drying rates (by 11.5% above and 8.5% below FSP) and increasing water uptake (up to 32% at 100 °C). It simultaneously promoted dimensional expansion (maximum 1.5%) while effectively inhibiting shrinkage and collapse, reducing total dry shrinkage by 10%. Additionally, ST significantly lowered wood hygroscopicity, decreasing the equilibrium moisture content (EMC) by an average of 24%, with the 100 °C/6 h group showing the lowest EMC (12.5%). The optimal steaming condition was determined to be 100 °C for 6 hours, achieving a balance of improved drying efficiency, reduced shrinkage and moisture absorption.

Structures made of wood are used extensively in applications that require mechanical reliability under variable environmental conditions. Several softwood species were investigated, including pine (Pinus sylvestris L.), spruce (Picea abies), and larch (Larix decidua). This study investigated the tensile deformation behavior of each species with a special focus on the mechanical energy demand of the tensile process. Samples were conditioned in an aqueous saline medium for defined exposure periods and compared with controls. The energy of deformation was determined from stress-strain relationships of tensile tests under identical loading conditions. Results indicate that saline conditioning alters the tensile response of the examined wood species in a species-dependent way. Tensile strength increased in pine wood after exposure, whereas spruce and larch showed different trends depending on conditioning duration. A wide range of tensile strengths was recorded for all samples, ranging from 5.4 MPa to 102.0 MPa. Controlled saline exposure significantly influences the mechanical behavior of softwood species, as indicated by the findings. Evaluating wood performance under modified environmental conditions, both deformation energy and strength parameters should be considered. The main novelty of this study is the introduction of an energy-based description of tensile deformation, in which the total tensile work is calculated from force-displacement relationships, enabling differentiation of specimens with similar tensile strengths but fundamentally different deformation and failure properties. A practical advantage of the proposed energy-based approach is that it provides additional insight into the deformation tolerance and failure behavior of saline-conditioned wood, thus enabling a more reliable assessment of material performance under unpredictable environmental conditions.

Commercially grown Eucalyptus plantation trees are mostly used for low value applications such as pulp, board, and energy products. The broad aim of the research described in this paper was to assess and develop the use of fast-growing Eucalyptus species in South Africa for use in high value engineered wood products. As a first step the variation in the most important wood and processing properties was established for two species (E. grandis and E. nitens) and a hybrid (E. saligna x urophylla) commonly used in commercial forestry in South Africa. Standing tree dynamic modulus of elasticity, log splitting and log dynamic modulus of elasticity (MOEdyn) were determined as a function of species, site, and log height position. Log and board end-splitting is arguably the defect having the largest value impact for Eucalyptus species processed into sawn timber. Log end-splitting was assessed using a visual splitting score which included length, opening width and position of splits in a log. The stiffness of timber is an important mechanical property affecting the grade and value of engineered wood products and was assessed firstly on standing trees using the Fakopp Treesonic device, and then on the logs using Fibre-gen’s Director HM200 device through evaluation of the acoustic wave speed (AWS) and subsequently MOEdyn. Linear mixed effects models were developed to examine the effects of species, site, and log height position on the MOEdyn of logs. All three factors played a role, to some extent, in the measured properties of logs. The research showed that an understanding of the variation of end-splitting and MOEdyn of Eucalyptus logs is important to select the best resource for engineered wood products and also to help improve processing decisions for each log resource.