Band 71, Heft 12

A noticeable proportion of low transcribed genes involved in wood formation in conifers may have been missed in previous transcriptomic studies. This could be the case for genes related to less abundant cell types, such as axial parenchyma and resin ducts, and genes related to juvenile wood. In this study, two normalized libraries have been obtained from the cambial zone of young individuals of Pinus canariensis C. Sm. ex DC, a species in which such cells are comparatively abundant. These two libraries cover earlywood (EW) and latewood (LW) differentiation, and reads have been de novo meta-assembled into one transcriptome. A high number of previously undescribed genes have been found. The transcriptional profiles during the growing season have been analyzed and several noticeable differences with respect to previous studies have been found. This work contributes to a more complete picture of wood formation in conifers. The genes and their transcription profiles described here provide a useful molecular tool for further studies focused on relevant developmental issues, such as wound response and the formation of traumatic wood, re-sprouting, etc., presumably related to those cells.

The genus Dalbergia contains approximately 250 species with many valuable trees being destroyed by targeted and illegal logging. DNA barcoding is a reliable method for the molecular identification of different species and resources conservation. In the present study, the specimen discrimination ability of internal transcribed spacer (ITS), mat K, rbc L and psb A- trn H barcoding were tested on Dalbergia sequences, downloaded from the National Center for Biotechnology Information (NCBI), and the combined barcoding ITS+ mat K+ rbc L was used to identify unknown specimens. It was found that ITS+ mat K+ rbc L have good discrimination rates based on the analysis methods best match (BM) and best close match (BCM). These barcodes also have the best performance concerning barcode gap distribution, and are able to discriminate unknown specimens from South-China. Furthermore, it was demonstrated that D. tamarindifolia and D. rubiginosa are also relatively close to sister-species D. pinnata and D. candenatensis within the phylogenetic Dalbergia tree. Considering the overall performance of these barcodes, we suggest that the ITS+ mat K+ rbc L region is a suitable barcode for identifying Dalbergia species.

High solvent recovery and monomeric sugar yield are essential for a viable biochemical conversion technology. The SO 2 -ethanol-water (SEW) or AVAP ® process has great potential to produce easily fermentable pulp fibers and sugars dissolved in the spent liquor stream. The SEW fractionation process is evaluated for delignification, xylan removal and potential reactions between ethanol and sugarcane straw (SCS) carbohydrates. α-ethyl-xyloside (aEX) and β-ethyl-xyloside (bEX) formed by reaction of ethanol with xylose are quantified. The fractionation experiments are carried out at 135°C, 145°C, and 155°C for 20–120 min at fixed liquor composition (SO 2 /EtOH/H 2 O=12:44:44, w/w) and liquor to feedstock ratio (4 l kg −1 ). The results are interpreted in terms of combined severity factor (CSF). Maximum ethyl xylosides (EX, or sum of aEX and bEX) and monomeric xylose concentrations are observed at CSF of 2.4±0.1. The maximum amount of EX in spent liquor accounts for nearly 1.4% of EtOH (feedstock basis). The implications for downstream recovery of EtOH and sugars from the spent liquor are discussed.

The stability and chemical reactions of lignans during alkaline cooking is not yet fully clarified although their degradation products may have a considerable effect on the pulp and its bleaching, such as spotting and color contamination. To fill this gap, a phenolic lignan (pinoresinol) and four non-phenolic furofuran lignans (gmelinol, paulownin, eudesmin and sesamin) were submitted to alkaline cooking at various conditions. The effect of cooking duration shows that non-phenolic lignans are more stable during a 3-h reaction time than pinoresinol. After a 24-h reaction, most of the lignans were decomposed or polymerized. The effect of cooking temperature shows that pinoresinol, eudesmin and sesamin are more susceptible to degradation with increasing temperature. The concentration of the alkaline liquors only affect significantly to pinoresinol because of its acidity. It was also observed that pinoresinol, gmelinol and eudesmin give rise to small amounts of vanillin and acetovanillone, while paulownin and sesamin were mainly polymerized or degraded. To confirm the reaction mechanism of the occurrence of acetovanillone in the reaction, 13 C-labeled pinoresinol was also submitted to alkaline cooking. It was revealed that the cleavage at β-β′ position occurred during alkaline reaction. The stability of these compounds during alkaline cooking are not affected by the hydroxyl group in the C-β′ position.

An occluding substance (gum) was observed in the vessels of Phellodendron amurense Rupr. and analysed by spectroscopic and chemical methods. Following safranin-alcian blue staining, the gum in sapwood (sW) turned to blue and in heartwood (hW) to red. The gum was studied in situ by UV and Raman microscopies, time-of-flight secondary ion mass spectrometry (TOF-SIMS). The gum was isolated by laser microdissection (LMD) and it was alkali hydrolysed and the degradation products were analysed by GC-MS. The staining experiments, and the UV and Raman microscopies indicated that the major component of the sW gum is constituted of polysaccharides, while in the hW gum the aromatic character is dominating. TOF-SIMS measurements were interpreted as showing the aromatic substances in the hW gum did not contain lignin. The GC-MS analysis revealed the presence of vanillic acid in the degradation products of hW gum.

The shear moduli (SM) of solid wood in longitudinal-radial (LR) and longitudinal-tangential (LT) planes were obtained via a torsional vibration (TV) test by varying the aspect ratios of Sitka spruce specimens and conducting subsequent numerical analyses. A pair of specimens with different aspect ratios was used to separate the SM in the LR and LT planes from each other, and the effect of the aspect ratio was examined. The experimental and numerical results indicated that the SM can be accurately obtained via TV test, when the aspect ratios of the specimens are appropriately determined.

Two specimen types, each from walnut and cherry wood, were prepared for tangential-radial (TR) and radial-tangential (RT) crack propagation systems at 65% of RH and 20°C before mode I and mode II fracture toughness was determined through Arcan tests. It was found that fracture toughness in mode I is in agreement with literature data. In the mode II test, however, the crack propagated in the direction normal to the shear plane and not parallel to it. The release rate of strain energy in terms of the opening failure in mode II was lower than that in mode I. It can be concluded that it is difficult to determine the fracture toughness of RT or TR propagation in hardwood specimens in mode II.

A new approach is presented in terms of the analysis of wood-cement (WC) compatibility, which is based on a similarity coefficient (C S ) that reflects the degree of resemblance between the curves of the “WC hydration temperature vs. time (24 h)” based on 15 g WC mixture and that of neat cement (C). This approach classifies clearly the compatibilities of different wood species on a scale of 0–100%, on which the most incompatible species have C S -values <5% and the upper compatibility class C S data around 95%, which is close to that of C, and which cannot be exceeded. The C S -value is well suited for modelling the inhibitory behaviour of all woods. In the discussion, the C S -approach is compared with other inhibitory indices proposed in the literature.