Sap Wood Research Articles

Characterization of water states and pore size distribution in Beijing poplar using nuclear magnetic resonance techniques

ABSTRACT This study employs nuclear magnetic resonance (NMR) techniques to elucidate the water states and pore size distribution within Beijing poplar (Populus beijingensis W. Y. Hsu) across various temperatures. By analyzing the variation in moisture content (MC) at different freezing temperatures, the proportion and distribution of cell wall pores were determined using the NMR Cryoporometry (NMR-C) method. The results show approximately 60% of the pores in both the heartwood (HW) and sapwood (SW) of Beijing poplar have diameters were 1.5 nm, while the proportion of pores with diameters greater than 4.6 nm was less than 10%. Moreover, the MC of both more freely bound water (C-water) and OH bound water (B-water) is observed to decrease exponentially with decreasing temperature. B-water in Beijing poplar is found to maintain a higher MC than C-water across the temperature range from −3 to −60°C, indicating greater resistance to freezing. The findings of this study contribute to a comprehensive understanding of water states in Beijing poplar. Also the pore size distribution of Beijing poplar provides reference data for the selection of wood chemical modification groups.

Enhancing outdoor comfort in urban hot climates: investigating the cooling impact of two tropical trees through shade provision and transpiration

ABSTRACT One key ecosystem service widely known and attributed to trees in the urban environment is their ability to provide shade through their canopies and undertake evapotranspiration cooling. These in turn contribute to reduced atmospheric temperatures. A lesser-known aspect with little quantitative data is the heterogeneous temperature environment beneath the canopies at pedestrian or street level where the cooling will benefit thermal comfort. This study was conducted throughout 2022. It collected data where air temperature was measured under the canopies of two urban tropical tree species, Samanea saman and Peltophotum pterocarpum, at three different heights, which were 1, 3 and 5 m, respectively, from the ground. This was to investigate whether crown architectures and the associated shade and cooling effects via transpiration can have a significant change in the surrounding temperature. The study observed surface and air temperatures coupled with meteorological data across cool, warm, and hot periods of the year. It was observed that soil temperature increased alongside increases in atmospheric temperatures with a more significant rise observed for P. pterocarpum despite the observation of greater wind speeds for both night and day at the site where this species was situated. The soil moisture potential data indicated the reverse where S. saman showed more negative values with the greatest increase under warm conditions. Interestingly, sap flow rates also indicated that P. pterocarpum had more efficient rates whether conditions were cool, warm, or hot, suggestive of more active transpirational cooling. This was despite a lower leaf area index, smaller crown volume and sap wood area for this species. Relationship analyses between sap flow and air temperatures at different heights under the canopies showed a positive correlation. This demonstrates that apart from shade provided by the canopies, transpiration is also an important parameter for cooling. The mean daytime air temperature indicated that the greatest cooling effect was experienced at the lowest level from the ground (at 1 m), and this was consistent for both species across cool, warm, and hot conditions with a significant cooling effect of between 2.3 and 4°C. Temperature data under the canopy (1 to 5 m from the ground) compared to the air temperature of the grass that was shaded indicated temperature differences of between 2.3 and 7.9°C at 5 m and between 1.9 and 5.6°C at 1 m (for both species) with a bigger reduction attributed to S. saman.

Physiological, Biochemical, and Molecular Analyses Reveal Dark Heartwood Formation Mechanism in Acacia melanoxylon.

Acacia melanoxylon is highly valued for its commercial applications, with the heartwood exhibiting a range of colors from dark to light among its various clones. The underlying mechanisms contributing to this color variation, however, have not been fully elucidated. In an effort to understand the factors that influence the development of dark heartwood, a comparative analysis was conducted on the microstructure, substance composition, differential gene expression, and metabolite profiles in the sapwood (SW), transition zone (TZ), and heartwood (HW) of two distinct clones, SR14 and SR25. A microscopic examination revealed that heartwood color variations are associated with an increased substance content within the ray parenchyma cells. A substance analysis indicated that the levels of starches, sugars, and lignin were more abundant in SP compared to HW, while the concentrations of phenols, flavonoids, and terpenoids were found to be higher in HW than in SP. Notably, the dark heartwood of the SR25 clone exhibited greater quantities of phenols and flavonoids compared to the SR14 clone, suggesting that these compounds are pivotal to the color distinction of the heartwood. An integrated analysis of transcriptome and metabolomics data uncovered a significant accumulation of sinapyl alcohol, sinapoyl aldehyde, hesperetin, 2', 3, 4, 4', 6'-peptahydroxychalcone 4'-O-glucoside, homoeriodictyol, and (2S)-liquiritigenin in the heartwood of SR25, which correlates with the up-regulated expression of CCRs (evm.TU.Chr3.1751, evm.TU.Chr4.654_667, evm.TU.Chr4.675, evm.TU.Chr4.699, and evm.TU.Chr4.704), COMTs (evm.TU.Chr13.3082, evm.TU.Chr13.3086, and evm.TU.Chr7.1411), CADs (evm.TU.Chr10.2175, evm.TU.Chr1.3453, and evm.TU.Chr8.1600), and HCTs (evm.TU.Chr4.1122, evm.TU.Chr4.1123, evm.TU.Chr8.1758, and evm.TU.Chr9.2960) in the TZ of A. melanoxylon. Furthermore, a marked differential expression of transcription factors (TFs), including MYBs, AP2/ERFs, bHLHs, bZIPs, C2H2s, and WRKYs, were observed to be closely linked to the phenols and flavonoids metabolites, highlighting the potential role of multiple TFs in regulating the biosynthesis of these metabolites and, consequently, influencing the color variation in the heartwood. This study facilitates molecular breeding for the accumulation of metabolites influencing the heartwood color in A. melanoxylon, and offers new insights into the molecular mechanisms underlying heartwood formation in woody plants.

Comparative physiological, biochemical, metabolomic, and transcriptomic analyses reveal the formation mechanism of heartwood for Acacia melanoxylon

Acacia melanoxylon is well known as a valuable commercial tree species owing to its high-quality heartwood (HW) products. However, the metabolism and regulatory mechanism of heartwood during wood development remain largely unclear. In this study, both microscopic observation and content determination proved that total amount of starches decreased and phenolics and flavonoids increased gradually from sapwood (SW) to HW. We also obtained the metabolite profiles of 10 metabolites related to phenolics and flavonoids during HW formation by metabolomics. Additionally, we collected a comprehensive overview of genes associated with the biosynthesis of sugars, terpenoids, phenolics, and flavonoids using RNA-seq. A total of ninety-one genes related to HW formation were identified. The transcripts related to plant hormones, programmed cell death (PCD), and dehydration were increased in transition zone (TZ) than in SW. The results of RT-PCR showed that the relative expression level of genes and transcription factors was also high in the TZ, regardless of the horizontal or vertical direction of the trunk. Therefore, the HW formation took place in the TZ for A. melanoxylon from molecular level, and potentially connected to plant hormones, PCD, and cell dehydration. Besides, the increased expression of sugar and terpenoid biosynthesis-related genes in TZ further confirmed the close connection between terpenoid biosynthesis and carbohydrate metabolites of A. melanoxylon. Furthermore, the integrated analysis of metabolism data and RNA-seq data showed the key transcription factors (TFs) regulating flavonoids and phenolics accumulation in HW, including negative correlation TFs (WRKY, MYB) and positive correlation TFs (AP2, bZIP, CBF, PB1, and TCP). And, the genes and metabolites from phenylpropanoid and flavonoid metabolism and biosynthesis were up-regulated and largely accumulated in TZ and HW, respectively. The findings of this research provide a basis for comprehending the buildup of metabolites and the molecular regulatory processes of HW formation in A. melanoxylon.

Effects of succinic acid impregnation on physical properties of sapwood and heartwood from plantation-grown short-rotation teak

The aim of this study was to improve the properties of 15-year-old short rotation teak wood using a succinic acid (SA) treatment without excessively increasing the weight gain. The samples were classified as sapwood (SW) and heartwood (HW). Samples were immersed in 10% concentration SA solutions (w/w), followed by vacuuming at -50 kPa for 30 minutes, and applying 7 M Pa of pressure for 2 hours. They were then analysed for specific gravity (SGs), dimensional stability, including tangential/radial ratio (T/R Ratio) and water absorption (WA), weight percent gain (WPG), chemical uptake (CU) and void volume filled (WF). Our results showed that SGs increased in treated SW and HW by 2.33% and 1.23%, respectively, as compared to the untreated wood (0.60 and 0.66). The increase in SGs was the result of SA penetration into wood cell walls. The WPG and CU values increased slightly to 5.54% and 0.87 g cm−3 for SW and 3.46% and 0.62 g cm−3 for HW, respectively. The greater increase of SGs in treated SW is due to a greater ease of treatability in SW than HW. The T/R ratio of treated HW decreased by 29.34% from the initial T/R ratio, whereas SW remained unchanged. The WA of treated SW and HW decreased by 42.67% and 55.46%, respectively compared to untreated wood. Treated wood performed better on dimensional stability, especially in terms of T/R ratio and WA values for HW. Our results show that the impregnation of short rotation teak wood with SA provides a significant increase on dimensional stability with a negligible increase in weight gain.

Inorganic component in oak waterlogged archaeological wood and volcanic lake compartments

Abstract. Waterlogged archaeological wood (WAW) is a rare and precious organic material that can hold outstanding cultural values. In order to protect WAW for the next generations, this material must be accurately characterised to set its proper conservation, storage and exhibition conditions in museum environments. In this study, the mineral content found in WAW retrieved in a volcanic lake was investigated by analysing wood ash through scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (SEM-EDS). This micro-destructive approach was coupled with morphological studies carried out through optical microscopy. SEM-EDS was also performed on the WAW and surrounding sediment to study the possible relationship between the mineral composition and the wood degradation state. The analysis revealed that calcium was the most abundant element in all poles, with weight percentages ranging between 24 % and 42 %. This element was more represented in heartwood (HW) than sapwood (SW). In sapwood the second most abundant element was arsenic. Sulfur, iron and potassium were present in all the analysed samples as well. Arsenic was also detected in the sediments; it was particularly concentrated in the samples taken near archaeological wood. The presence of this element can be linked to the volcanic origin of the lake, and its high concentration points to bioaccumulation processes induced by bacteria (erosion bacteria and sulfate-reducing bacteria) and biogeochemical processes favouring precipitation of insoluble compounds. The present work is the first investigation of the mineral content in archaeological wood establishing a contingent relationship with the surrounding volcanic lake sediments.

Effect of the Fungus Neoscylitiadium dimidiatum Penz. Reduction of Dry Weight and Specific Weight of Sapwood and Heartwood of the Trunks of Populus and Eucalyptus Trees

The study was carried out in the Forest Diseases Laboratory, Department of Forest Sciences, College of Agriculture and Forestry, University of Al Mosul. During the academic year 2021-2022, the Sakla wood is available in the wood stores in the city of Mosul. The study aimed at the effect of decay fungi on some local commercial woods, including populus and Eucalyptus The results of the field survey of wood stores in the city of Mosul showed that most of the wood was infected with brown rot fungus. As the severity of the infection varied in different proportions, the percentage of infection of populus wood columns was 75%, and the percentage of infection of Eucalyptus wood columns was 40%. The fungus Neoscylitiadium dimidiatum penz. caused a decrease in the dry weight of populus wood and Eucalyptus columns from the first month of incubation and continued gradually until the fifth month As the percentage of loss in the fifth month was 4.41% for the populus poles, and the percentage of loss was 3.33% for the Eucalyptus poles. The increase in the losses in the weight of the sap wood continued during the incubation stages and to a greater degree than the increase in the loss percentages in the heart wood.

High-Quality RNA Extraction and Evaluation of Reference Genes for qPCR Assay of <i>Pinus sylvestris</i> L. Trunk Tissues

Scots pine (Pinus sylvestris L.) is a species of tree with heartwood (HW), which is forming during aging of sapwood (SW). Due to clear-cut border between SW and HW P. sylvestris should be used as a model woody plant for studying patterns of HW formation. Currently, molecular genetic methods are used to study the processes of trunk tissues formation in woody plants often. A feature of trunk tissues of coniferous trees is a high content of secondary metabolites, a low content of nucleic acids, and potential partial degradation of RNA. In this work we discuss the choice of most successful method for extraction a high-quality RNA for real-time PCR (RT-PCR) in P. sylvestris trunk tissues along the radial vector “conductive phloem/cambial zone – differentiating xylem – exterior part of SW (1–2 annual rings) – interior part of SW (1–2 annual rings afore transition zone (TZ)) – TZ (2 annual rings afore HW)” for reproducible RT-PCR data. The expression stability of six potential reference genes (Actin1, α-Tubulin, β-Tubulin, Ef1a, GAPDH, UBQ) was assessed in all describe tissues. Differences in expression levels of target genes are shown by data normalization using reference genes with different stability of expression.

Plant-Programmed Cell Death-Associated Genes Participation in Pinus sylvestris L. Trunk Tissue Formation.

Molecular genetic markers of various PCD (programmed cell death) variants during xylo- and phloemogenesis have been identified for the first time in Scots pine under lingonberry pine forest conditions in Northwest Russia (middle taiga subzone). PCD is a genetically determined process. Gene profiles of serine and cysteine proteases (endopeptidases), endonucleases, and metacaspases families are often considered markers of the final xylogenesis stage. In the present study, we examined the gene expression profiles of the BFN (bifunctional endonuclease) family-BFN, BFN1, BFN2, BFN3, and peptidase (cysteine endopeptidase, CEP and metacaspase, MC5) in the radial row, in addition to the vascular phloem and cambium (F1), differentiating xylem (F2), sapwood (SW), and transition zone during the active cambial growth period of uneven-aged pine trees (25-, 63- and 164-cambial age (c.a.) years old). We have shown that the expression patterns of the PCD-related genes did not depend on the cambial age but were largely determined by plant tissue type. In the radial row F1-F2-SW, we studied the activities of enzymes, including sucrose in metabolism (sucrose synthase, three forms of invertase); antioxidant system (AOS) enzymes (superoxide dismutase, catalase); and peroxidase andpolyphenol oxidase, which belonged to AOS enzymes and were involved in the synthesis of phenolic components of cell walls. The activity of the enzymes indicated that the trunk tissues of pine trees had varying metabolic status. Molecular genetic PCD regulation mechanisms during xylem vascular and mechanical element formation and parenchyma cells' PCD during the formation of Scots pine heartwood were discussed.

Integrated Transcriptomic, Metabolomic, and Physiological Analyses Reveal New Insights into Fragrance Formation in the Heartwood of Phoebe hui.

Phoebe hui is an extremely valuable tree that is the main source of the fragrant golden-thread nanmu wood. Although the fragrance of wood has been investigated in several trees, the potential substances and gene regulation mechanisms that are involved in fragrance formation are poorly understood. Here, three radial tissues, sapwood (SW), heartwood (HW), and the transition zone (TZ) in between them, were compared via integrative physiological, volatile-metabolomic, and transcriptomic analyses to identify the key metabolites and regulatory mechanisms involved in fragrance formation. During heartwood formation, gradual starch grain loss was accompanied by the deposition of lipids and extractives in the cell lumen. Extracts of terpenoids were synthesized and accumulated in the heartwood, including monoterpenoids (limonene and p-cymene) and sesquiterpenes (cubebene and guaiadiene); these were identified as being closely related to the special fragrance of the wood. Additionally, the expression of transcripts showed that the genes related to primary metabolism were specifically upregulated in the SW, whereas genes annotated in terpenoid biosynthesis were specifically upregulated in the HW. Therefore, we speculated that terpenoid biosynthesis occurs in situ in the HW via the HW formation model of Type-III (Santalum) using the precursors that were produced by primary metabolism in the SW. The expression levels of transcription factors (e.g., MYB, WRKY, and C2H2) acted as the major regulatory factors in the synthesis of terpenoids. Our results explain the special fragrance in P. hui and broaden the current knowledge of the regulatory mechanisms of fragrance formation. This work provides a framework for future research that is focused on improving wood quality and value.

Variation of wood color and chemical composition in the stem cross-section of oak (Quercus spp.) trees, with special attention to the sapwood-heartwood transition zone

The transformation of sapwood (SW) into heartwood (HW) during ageing of wood tissues is the result of physiological and biochemical changes initiated in the transition zone (TZ). These changes contribute to the evolution of active (living) wood cells in SW into less/non-active (dead) wood cells in HW. Previous studies established that the biosynthesis of extractive contents is the most prominent process that occurs in the TZ. To improve our understanding of the extent and characteristics of the TZ in oak wood, the present study reports the results of color parameters (using CIELab color space) and molecular structure and composition of polysaccharide and lignin compounds (using FTIR-ATR and Py-GC–MS). For that purpose, six wood cores from individual living oak (Quercus spp.) trees were collected from two forests with similar environmental conditions, located in the Basque Country (Northern Spain). The color data indicated significant differences between SW, TZ and HW by showing that SW samples were characterized by higher hue (h°) and lower redness (a*) values than the HW, and intermediate values for the TZ. They also suggested that the variations of wood color from SW to HW occur gradually, along a wide TZ counting 4–10 measurement points in a row, depending on the tree. Furthermore, FTIR and Py-GC–MS data gave evidence of the variation trends of polysaccharide and lignin contents in the radial direction, through various FTIR ratios (1735/1325, 1590/1735, 1590/1230, and 1230/1325 cm−1) and one pyrolysis ratio (acetic acid/total polysaccharide: Ps01/Tot_Ps). The observed variations in this present study suggest that the cross-sectional transition patterns can be related to the continuous lignification process of xylem parenchyma cells, as well as the storage of polysaccharide compounds. These results contribute to our fundamental knowledge on the TZ, which may be valuable in research and industrial applications where a clear delimitation of sapwood and/or heartwood is required.

Compressive Strength of Aged Timber Members in Traditional Building: Considering Differences in Heartwood and Sapwood

This paper compares the parallel-to-grain compressive strengths of wood sample specimens with defects with those of the associated timber log samples. The Chinese fir (Cunninghamia lanceolata) was examined using the static test method. We analyzed the effects of sampling position along the radial direction of the log sample and the age of timber on the parallel-to-grain compressive strength. We then developed time-dependent strength models of the heartwood (HW) and sapwood (SW). These models can be used to evaluate the strength of an aged timber member, using only the service duration, without taking material samples. The degradation of compressive strength over time was then analyzed using an existing multivariate time-dependent model that includes the stress level. The failure strength of the HW was found to be close to that of the SW when at low stress levels. The estimates of the compressive strength of timber members based on these models were better than those recommended by the Chinese National Standard.

Changes in the intensity of heartwood formation in Scots pine (Pinus sylvestris L.) ontogenesis

Summary An essential stage in woody plant ontogeny (heartwood (HW) formation) determines tree resistance to weather conditions, wood quality (moisture, colour, resistance to biodegradation), and regulates the proportion of functionally active sapwood (SW) in the total trunk biomass. In this study, the patterns of HW formation depending on tree age and cambial age within the same tree were studied in the North-West of Russia in Scots pine in a lingonberry pine forest. It is shown that HW either repeats the trunk profile or shows a maximum proportion on average at the height of 1.5 m. Models using the square root transformation and logarithm transformation have been proposed to predict the number of annual rings in HW depending on the cambial age. Multiple regression is proposed to predict the radial width in HW. Validation of the developed models on random trees gave a good result. HW formation begins at the age of 17–18 years and continues at the rate of 0.3 rings per year for 20–30-year-old trees, 0.4–0.5 rings per year for 70–80-year-old trees, and about 0.7 rings per year for 180-year-old trees. The lifespan of xylem parenchyma cells ranged from 10–15 years in 20-year-old trees to 70 years in 180-year-old trees. At the age of the previous felling (70–80 years) the HW area in the trunk biomass is about 20%, and in 180-year-old pine forests, it increases to 50%. These data can be used to assess the role of old-growth forests in carbon sequestration.

Urbanization intensifies tree sap flux but divergently for different tree species groups in China.

In recent years, positive and negative effects of urbanization on forest ecosystem have been reported by many studies, while some uncertainties about the impact of urbanization-induced spatial heterogeneity of environmental factors on forest systems still remain unclear. In this study, we analyzed the urbanization effects on sap flux of a common subtropical evergreen tree species Schima superba along an urban-rural gradient in Guangdong Province, South China, and identified the consistency of these results among different groups (evergreen, deciduous, and coniferous species) using data from 83 previously published studies in China. The mean sap flux density (Fd) of S. superba in Xiaoqingshan (XQS), Heshan (HS), Dinghushan (DHS), and Shimentai (SMT), along the urban-rural gradient was 40.9gm-2s-1, 32.1gm-2s-1, 17.0gm-2s-1, and 17.5gm-2s-1, respectively, presenting a decreasing trend with the diminishing urbanization. This pattern in Fd tended to enlarge with tree size and was well confirmed by the enhanced leaf transpiration rate (by 119%) and photosynthetic rate (by 8.8%) for the S. superba in another urbanization gradient from the urban (Hangzhou, denoted as "HZ") to rural sites (Jiande, denoted as "JD") in Zhejiang Province, East China, which has similar climatic condition and urbanization with Guangdong Province. We attributed such positive effects to the decreased sapwood density and specific leaf area (SLA), as well as the increased Huber value (sap wood area/leaf area) and the sap wood specific hydraulic conductivity (KS). We also found that pollutant emission exerted more impact on Fd than climatic factors change, since the variation of the latter was not large enough to cause significant change of Fd under the same climatic zone. In addition, we conducted a principal component analysis (PCA) based on the published 83 studies. Results showed Fd of evergreen tree species was related positively to principle 1 and negatively to principle 2, respectively, whereas the Fd of deciduous broadleaf and coniferous tree species was positively and negatively related to both principles, respectively. This study demonstrated the potential impact of urbanization-related pollutant emission changes on water use of forest trees and the growth among different groups.

Corrective Interventions to End-Splitting and Surface Cracking in Kenya Grown <i>Eucalyptus grandis</i> Poles

This study determined the effect of three pole pre-drying handling techniques, on end-splitting and surface checking in Eucalyptus grandis poles from highland and low land areas in Kenya. A total of 144 Eucalyptus grandis trees were sampled from two sites; Kericho, representing the wet highlands and Londiani representing the drier lowlands regions of Kenya. Pole samples from both sites were subjected to the three pre-drying handling techniques for the first 30 days after felling and allowed to dry to the required moisture level under observations. The number of end splits and surface checks on each sample pole were counted and the length of the worst ones was measured in millimeters after every 15 days until all the poles reached 25% MC. The sap wood and heart wood ratios were determined from selected samples. Results showed that on the overall, poles from high land areas had the highest sapwood proportions and similarly had the highest number and the longest end splitting and surface checks. On the other hand, pre-drying techniques that allowed felled trees to dry slowly with their foliage intact for the first 30 days of felling produced the best quality poles, with fewer and shallower end splits and surface checks. The study recommended that felling and leaving poles to dry slowly with foliage intact be considered in reducing losses incurred as a result of wood stresses during drying of poles.

Awareness and adoption level of improved practices by pear growers of Tarn Taran district

Pear is one of the most important fruit crops of the temperate region. In Punjab, a low chill variety Patharnakh, has been widely cultivated and become the commercial fruit crop. The present investigation was conducted to assess the awareness and adoption of recommended pear production practices to narrow the adoption gaps so as to achieve sustainable production of quality fruits in Tarn Taran District to evaluate the effect of different technology variables on the awareness score and adoption level of recommended package of practices for pear. The study showed that the respondents along with awareness adopted some of the recommended practices for pear cultivation on priority such as timely irrigation to the plants (As = 1.0; Al =2.6), use of FYM along with chemical fertilizers and timely pruning and training of the fruit plants having good awareness and adoption values. However, they were moderate in terms of weed management (As = 0.58; Al =1.26) and practice of proper packaging and marketing of fruits (As = 0.56; Al =1.20). On the other side, management of mite (As = 0.06; Al =0.10) followed by use of micronutrients as balanced nutrition (As = 0.10; Al =0.22), use of Bordeaux mixture for sap wood and root rot and use of potassium nitrate (KNO3) for better yield were practices with least awareness and adoption values. The results indicated that, a mere awareness of technology does not lead to adoption. This gap can be bridged by imparting practical know-how with hands-on training to pear growers in niche area.

Compatibility of preservative with adhesive in Eucalyptus grandis laminates

ABSTRACT The fundamental factors responsible for the complexities in adhesive bonding of preservative-treated wood are predominantly wood species, preservative composition, and adhesive system. It is post-effect of these factors that process variables such as assembly times and bonding pressure exert secondary influences on adhesive-bond development in preservative-treated laminates. Hence, this study investigated the effect of copper azole (CA) and disodium octaborate tetrahydrate (DOT) impregnations on E. grandis heartwood (HW) and sapwood (SW) bonding with melamine–urea–formaldehyde and polyurethane adhesives. Based on the adhesives and bonding conditions investigated, the CA and DOT-treated E. grandis laminates do not satisfy at least one of the shear strength and delamination requirements according to EN 14080:2013. Contrary to delamination, shear strength was significantly affected by the HW–SW difference. This study established the basis for further considerations on adapting bonding conditions for improved adhesive-bond performance in CA and DOT-treated E. grandis laminates towards manufacturing durable hardwood composite for tropical and subtropical environments.

Chemical characterization of sapwood and heartwood of Fraxinus angustifolia growing in Algeria

The result of this study is the chemical characterization of sapwood (SW) and heartwood (HW) of Fraxinus angustifolia native to Algeria. Lipophilic and hydrophilic extractives were isolated by means of an accelerated solvent extractor (ASE) using hexane and the acetone/water mixture respectively. The acid hydrolysis and methanolysis methods were used to determine cellulose and hemicelluloses contents. The Tappi Standards T 222 and UM 250 allowed Klason and acid-soluble lignin quantification respectively. Alkaline hydrolysis of wood samples followed by HPLC analysis was performed to determine the acetyl groups. The method detailed in TAPPI T 211 (2002) for determining the ash content was used. It was found that the SW and HW of Fraxinus A. had almost similar amounts of the main components, averaging 40.00 wt% cellulose, 28.00 wt% hemicelluloses within 18.00 wt% of xylan, 22.00 wt% lignin, 3% extractives and 0.83 wt% ash. However, the HW contained more triglycerides (0.08 wt%) than the SW (0.02 wt%). On the other hand, mannitol was the most predominant hydrophilic extractive in SW (1.60 wt%) than in HW (1.02 wt%). These findings are useful for practitioners in the paper, biofuel, cosmetics, food, pharmaceutical and chemical industries for the assessment of Fraxinus A. wood chemical treatment parameters.

Wood Extractives of Silver Fir and Their Antioxidant and Antifungal Properties.

The chemical composition of extractives in the sapwood (SW), heartwood (HW), knotwood (KW), and branchwood (BW of silver fir (Abies alba Mill.) was analyzed, and their antifungal and antioxidant properties were studied. In addition, the variability of extractives content in a centripetal direction, i.e., from the periphery of the stem towards the pith, was investigated. The extracts were analyzed chemically with gravimetry, spectrophotometry, and chromatography. The antifungal and antioxidative properties of the extracts were evaluated by the agar well diffusion method and the diphenyl picrylhydrazyl radical scavenging method. Average amounts of hydrophilic extractives were higher in KW (up to 210.4 mg/g) and BW (148.6 mg/g) than in HW (34.1 mg/g) and SW (14.8 mg/g). Extractives identified included lignans (isolariciresinol, lariciresinol, secoisolariciresinol, pinoresinol, matairesinol) phenolic acids (homovanillic acid, coumaric acid, ferulic acid), and flavonoids epicatechin, taxifolin, quercetin). Secoisolariciresinol was confirmed to be the predominant compound in the KW (29.8 mg/g) and BW (37.6 mg/g) extracts. The largest amount of phenolic compounds was extracted from parts of knots (281.7 mg/g) embedded in the sapwood and from parts of branches (258.9 mg/g) adjacent to the stem. HW contained more lignans in its older sections. Hydrophilic extracts from knots and branches inhibited the growth of wood-decaying fungi and molds. KW and BW extracts were better free radical scavengers than HW extracts. The results of the biological activity tests suggest that the protective function of phenolic extracts in silver fir wood can also be explained by their antioxidative properties. The results of this study describe BW as a potential source of phenolic extractives in silver fir.

Comparative metabolomics analysis reveals the color variation between heartwood and sapwood of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook

To reveal the correlation between the metabolites profiles and the wood color variation, metabolomics analysis of heartwood (HW) and sapwood (SW) of Chinese fir at two different ages was performed. The metabolite profiling was obtained using ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometer (UPLC/Q-TOF-MS/MS). The results demonstrated that a total of 12,581 metabolites were obtained, of which 850 were annotated to the Human Metabolome Database (HMDB). Principal component analysis (PCA) and orthogonal partial least squares-discriminantion analysis (OPLS-DA) displayed a distinctly variation from HW group and SW group, 21 phenolic compounds including flavonoids, coumarins and derivatives, and stilbenes accumulated most in the HW group, which could be responsible for the darker of HW. As for variation in metabolites between tree ages, the HW and SW from older Chinese fir accumulated greater frequency of secondary metabolites than those from the younger ones. The metabolic pathway enrichment analysis revealed the flavonoid biosynthesis pathway extremely changed between the groups of HW and SW, HW-24Y and HW-19Y, and SW-24Y and SW-19Y, respectively, implying that the identified flavonoid metabolites in this study could clarify the wood color difference between HW and SW in kaihua 3 clone Chinese fir. The results of this study may provide valuable information regarding how the metabolic compositions and the potential of flavonoid pathway alter the wood coloring.