Volume 73, Issue 6

Aquilaria Lam. is an important group of trees that produce agarwood, which is widely used for manufacturing medicine, perfumes and incense. The members of the genus Aquilaria are close to being extinct due to illegal harvesting and are now protected in many countries. In this study, five DNA barcodes [internal transcribed spacer (ITS), maturase K ( mat K), psb A- trn H, ribulose bisphosphate carboxylase ( rbc L) and trn L- trn F] and their combinations were evaluated for the discrimination of the major (16 out of 21) species of Aquilaria based on three criteria: sequence variation, genetic distances and the discrimination ability. In addition, we attempted to determine the phylogenetic relationship between Aquilaria and Gyrinops species using three phylogenetic analysis methods. We observed that the combination barcode ITS+ trn L- trn F had a good discrimination ability based on the best match and best close match methods, provided more genetic information, and clearly indicated the comprehensive phylogenetic relationship between most Aquilaria and Gyrinops species. Considering the overall performance of these barcodes, the ITS+ trn L- trn F is a suitable barcode for the identification of Aquilaria species.

Podocarpus latifolius [(Thunb.) R.Br. ex Mirb.], also known as real yellow wood, is a large evergreen tree with exceptionally high-quality wood. It is a member of the Podocarpaceae family, which includes many species widely grown for wood pulp as well as timber for construction. Despite its importance, studies focusing on its genetic characterization and molecular biology are limited. Therefore, this study reports the complete plastome of P. latifolius , which is a circular molecule of 134 020 base pairs (bp) in length, lacking a quadripartite structure. The P. latifolius plastome encodes 117 unique genes, consisting of 82 protein-coding genes, 31 transfer RNA genes and four ribosomal RNA genes. The analysis showed that the Podocarpaceae plastomes have experienced some intron and gene losses, inversions, and inverted repeat (IR) loss resulting in a diverse plastome organization at the species and genus levels. Therefore, to understand the extent of these genomic rearrangements, more sampling of the Podocarpaceae plastomes is necessary. A total of 149 editing sites were predicted in 28 genes, all of which were C to U conversions. Moreover, a total of 164 simple sequence repeats (SSRs) were identified in the P. latifolius plastome, the majority being mononucleotide repeat motifs with A/T sequence predominance. Overall, the data obtained in this study will be useful for population genetics, evolutionary history and phylogenetic studies of the species in this genus.

Plantations of naturally durable timber species could substitute unsustainably harvested wood from tropical forests or wood treated with toxic preservatives. The New Zealand Dryland Forests Initiative (NZDFI) has established a tree-breeding program to develop genetically improved planting stock for durable eucalyptus plantations. In this study the durable heartwood of Eucalyptus bosistoana , Eucalyptus globoidea and Eucalyptus argophloia was characterized by near infrared (NIR) spectroscopy and NIR data was calibrated with the extractives content (EC), determined by accelerated solvent extraction (ASE) extraction, by means of a partial least squares regression (PLSR) model. It was possible to predict the EC content in the range of 0.34–18.9% with a residual mean square error (RMSE) of 0.9%. Moreover, the three species could also be differentiated by NIR spectroscopy with 100% accuracy, i.e. NIR spectroscopy is able to segregate timbers from mixed species forest plantations.

Currently, there is an increasing interest in Mexico to grow teak in large-scale plantations. Teak is recognized for its natural durability combined with high mechanical strength. The present study aims at determining the quantitative and qualitative properties of teak wood for several age classes and provenances, originating mainly from three localities of south eastern Mexico, while the focus was on the extractives and the natural durability of teak samples. The percentage of heartwood (hW) formed by the plantation trees was within the range reported elsewhere for the corresponding age classes, while the hW% was in relation with the tree height and age. Further trends observed were: lower topo-chemical absorbance that was measured by ultraviolet microspectrophotometry (UMSP) of the inner hW compared to the outer hW; no clear correlation between the age and origin and the extractives’ composition accumulated in the hW; abundant presence of tectoquinone irrespective of the age and provenance; and finally, high resistance against white rot (WR) and brown rot (BR) fungi regardless of the age or provenance.

For robotic fabrication of wooden structures, the simple, quick and tight joining of elements can be solved using swelling hardwood dowels. This topic has been the focus of the present study, and the set-recovery capacity of densified wood (dW) as dowel material was investigated. European beech was compressed in the radial direction at 103°C and 10% moisture content (MC) to a compression ratio of 40%. Multiple swelling and shrinkage cycles were applied to measure swelling behavior, swelling pressure development and combined swelling and creep under compressive loading. It has been demonstrated that dW shows increased swelling and more persisting swelling pressures than native wood (nW). The set-recovery prevents significant contact-stress relaxation over multiple cycles of MC change. Application as a structural joining element for robotic fabrication was studied by shear lap joint tests on round double-dovetail swelling dowels.

Biphenyl structures (5–5 linkages) are one of the significant structural units in plant cell wall lignin. They can potentially play a role in providing branch points in lignins and influence the polymer structure of lignins. Variation of the biphenyl content was investigated for 21 wood species by alkaline nitrobenzene oxidation. The total yields of biphenyl-type products were similar among the six softwoods, and at least 6% of the phenylpropanoid units in lignin were involved in the biphenyl structures (>0.06 per C 6 -C 3 ). The biphenyl product yield of the 15 hardwoods ranged widely (0.002–0.05 per C 6 -C 3 ) and was lower in species having a higher syringyl/guaiacyl ratio (i.e. a species with less guaiacyl units). In addition, the proportion of biphenyl products in all guaiacyl-type products was not constant but decreased as the proportion of syringyl units increased. This indicates that the content of guaiacyl units is not likely the only factor influencing the biphenyl content.

The release of harmful volatiles, such as formaldehyde, is a major issue of the chemical modification of wood that limits the utilization of the modified wood in indoor environment. In this study, glucose (Glc) was activated with Fenton’s reagent under various conditions and the chemical structure of the activated Glc was characterized. Also, the reactivity of the activated Glc toward filter paper as a wood model was evaluated. The results show that the H 2 O 2 concentration controlled the activation ratio of Glc. Additionally, the Fe(II) concentration and activation temperature determined mainly the oxidation reaction rate. The Fenton reaction in an acidic solution resulted in higher activation efficacy of Glc and better fixation in the filter paper, compared to the reaction in an alkaline solution. The Glc cannot be fixed in the filter paper, but the activated Glc exhibited a fixation ratio of up to 48.2% due to the formation of carboxyl and aldehyde groups, as evidenced by Fourier-transform infrared (FTIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS). It was demonstrated that activation of Glc with the Fenton’s reagent is a feasible and eco-friendly approach and the activated products have a high potential for wood modification.

In order to close the water cycle in pulp mills with condensates instead of fresh water, the malodorous/hazardous volatile compounds and colored substances have to be removed by appropriate efficient methods. In the present work, the condensate from the evaporation of black liquor (BL) from a kraft mill was purified by a batch adsorptive process by means of commercial activated carbon (AC). The effluent was found to contain a wide range of aromatic and organosulfur volatile compounds, including toluene, ethylguaicol, syringaldehyde, dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), 2,3-dimethylthiophene, benzothiol and benzothiophene derivatives. Methanol was the major volatile organic component in the condensate (201 mg l −1 ), which was, however, poorly adsorbed on the AC surface. Aromatics and organosulfur contaminants were adsorbed almost completely in 2–5 min at 23°C under the optimized AC load (900 mg l −1 ). The treatment allowed the elimination of up to 99% of the obnoxious odor, color and turbidity of the condensate. The adsorption equilibrium followed the Langmuir model and the pseudo-second-order kinetics. The new process could be incorporated in the pulp mill with relatively low additional reagent costs.

An inorganic adhesive mix consisting of MgO, MgCl 2 , Na 2 SiO 3 , Na 3 PO 4 was used to prepare mineral bound particleboard (mbPB) without formaldehyde emission and with excellent fire retardant and smoke suppression properties. The mechanical properties, interior microstructure, fire retardancy and smoke suppression behavior of the mbPB was investigated based on scanning electron microscopy (SEM) and cone calorimetric observations. The results showed that the presence of massive hydrates of the inorganic adhesive covers the mbPB particles, which are responsible for the positive effects. The effective smoke suppression was accompanied by an essential carbon monoxide (CO) and carbon dioxide (CO 2 ) decrement in the gaseous effluents. The mbPBs are suitable as indoor material for wall, floor, and furniture as fire retardant and smoke suppressive materials.

Proper utilization of recycled rubber is of high environmental and resource concern. In this study, a composite (COMP) was created based on high-density fiberboard sawdust (HDFS), ground tire rubber (GTR) particles and virgin high-density polyethylene (HDPE) with the ratio of HDFS:GTR:HDPE=30:21:49 and with 1% PE wax as lubricant. A dual coupling agent system, i.e. bis-(triethoxysilylpropyl) tetrasulfide (TESPT, up to 5% based on the COMP total weight) together with maleated polyethylene (MaPE, 3, 5 and 8% based on the COMP weight), was applied. The rheological properties of the hybrid during the extrusion process was evaluated in a HAAKE miniLab rheometer, and the bending and tensile properties of injected COMP were tested. The results showed that addition of MaPE and TESPT has an evident influence on the shear viscosity and stress of the COMP fluid, and the two coupling chemicals have synergetic effects. Increased content of MaPE and/or TESPT improved the tensile and bending strength of the COMP, while excessive addition of TESPT (over 1%) decreased the bending modulus. To conclude, a dual coupling system, 5% MaPE plus 1% TESPT, seems to be advantageous for the COMP behavior.