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There is controversy concerning the presence of xyloglucans in gelatinous (G) layers of Populus spp. tension wood, particularly in mature G-fibers. Transmission electron microscopy (TEM) immunogold localization combined with LM15 antibody (recognizes XXXG-motif of xyloglucans, heptasaccharide) was used to investigate the distribution of xyloglucan epitopes in both transverse and radial sections of P. tremula tension wood. Results provided clear evidence for the presence of xyloglucans in both mature and developing G-layers. Developmental decrease of LM15 epitope localization in G-layers was also detected during G-fiber maturation. High magnification TEM observations showed specific localization of LM15 epitopes on newly synthesized cellulose macrofibrils present in the innermost layer of developing G-layers adjacent to the cell lumen, suggesting linkage between xyloglucans and cellulose macrofibrils. Possible mechanisms were discussed for developmental changes of xyloglucan with respect to the different results reported in the literature. [ABSTRACT FROM AUTHOR]

Angiosperm trees produce tension wood to actively control their vertical position. Tension wood has often been characterised by the presence of an unlignified inner fibre wall layer called the G-layer. Using this definition, previous reports indicate that only one-third of all tree species have tension wood with G-layers. Here we aim to (i) describe the large diversity of tension wood anatomy in tropical tree species, taking advantage of the recent understanding of tension wood anatomy and (ii) explore any link between this diversity and other ecological traits of the species. We sampled tension wood and normal wood in 432 trees from 242 species in French Guiana. The samples were observed using safranin and astra blue staining combined with optical microscopy. Species were assigned to four anatomical groups depending on the presence/absence of G-layers, and their degree of lignification. The groups were analysed for functional traits including wood density and light preferences. Eighty-six% of the species had G-layers in their tension wood which was lignified in most species, with various patterns of lignification. Only a few species did not have G-layers. We found significantly more species with lignified G-layers among shade-tolerant and shade-demanding species as well as species with a high wood density. Our results bring up-to-date the incidence of species with/without G-layers in the tropical lowland forest where lignified G-layers are the most common anatomy of tension wood. Species without G-layers may share a common mechanism with the bark motor taking over the wood motor. We discuss the functional role of lignin in the G-layer. [ABSTRACT FROM AUTHOR]

Tension wood (TW) in hybrid aspen trees forms on the upper side of displaced stems to generate a strain that leads to uplifting of the stem. TW is characterized by increased cambial growth, reduced vessel frequency and diameter, and the presence of gelatinous, cellulose-rich (G-)fibers with its microfibrils oriented parallel to the fiber cell axis. Knowledge remains limited about the molecular regulators required for the development of this special xylem tissue with its characteristic morphological, anatomical, and chemical features. In this study, we use transgenic, ethylene-insensitive (ETI) hybrid aspen trees together with time-lapse imaging to show that functional ethylene signaling is required for full uplifting of inclined stems. X-ray diffraction and Raman microspectroscopy of TW in ETI trees indicate that, although G-fibers form, the cellulose microfibril angle in the G-fiber S-layer is decreased, and the chemical composition of S- and G-layers is altered than in wild-type TW. The characteristic asymmetric growth and reduction of vessel density is suppressed during TW formation in ETI trees. A genome-wide transcriptome profiling reveals ethylene-dependent genes in TW, related to cell division, cell wall composition, vessel differentiation, microtubule orientation, and hormone crosstalk. Our results demonstrate that ethylene regulates transcriptional responses related to the amount of G-fiber formation and their properties (chemistry and cellulose microfibril angle) during TW formation. The quantitative and qualitative changes in G-fibers are likely to contribute to uplifting of stems that are displaced from their original position. [ABSTRACT FROM AUTHOR]

Beech wood has a high frequency of defects such as red heartwood, reaction wood (tension wood). For the experimental measurements four logs without visible defects like red heartwood, which can noticeably affects the measurements' results were qualified. The drying medium temperature in the first phase of the process before the moisture content of the specimens fell below the FSP was maintained at 45 °C. Then, the temperature was gradually increased to the maximum value 65 °C. The results showed that different initial wood moisture content does not affect to final value of tension and normal wood. The colorimetric parameter L* was much higher for tension wood. After steaming, there were greater differences in the colorimetric parameters, respectively, a* and b*. After drying the difference of all colorimetric parameters between tension and normal wood was significantly less. The color changes were only noticed in the surface layers of specimens. Differences were small, and thus, the impact of the tension wood on the color changes was not confirmed. However, since the lightness of tension wood plays a key role for its visual detection, it may be adequate to only measure the lightness parameter (L*). [ABSTRACT FROM AUTHOR]

The objective of this study was to characterize the wood anatomical structure of a rubber tree clone, under the influence of two different canopy grafts. The following rubber trees were selected in the system of a doublegrafted PB 311 + FX 2784 and PB 311 + MDF 180. For each tree, discs of wood were cut from the affected branch immediately below the insertion of clone at right angles to the axis, from which the regions corresponding to tension, in opposite and normal wood, were identified. The anatomical analyses were conducted in accordance with the standards established by the International Association of Wood Anatomy Committee. The Kruskal-Wallis nonparametric test was applied for multiple comparisons among the types of woods and radial positions studied, at 5% of significance. Still, multivariate associations were assessed among the anatomical characteristics of both double-grafted rubber trees, by means of a two-step cluster analysis. Quantitative morphological differences were observed in the wood cells of the double-grafted studied clones. The ray height and the vessels diameter were the most important morphologic characteristics for the distinction. The canopy clone exhibited the ability to modulate the quantitative anatomical characters of the panel clone, depending on the plant's needs. [ABSTRACT FROM AUTHOR]

Tree stems deviating from the vertical position react by the formation of tension wood (TW) or compression wood (CW), which are called in general as reaction wood (RW), in which the cells are modified chemically and anatomically. The focus of the present work is the mechanical behavior of TW in five 37-year-old Eucalyptus species, which were grown on a planting area with an average slope of 28% leading to decentralized pith in the trees, which is an unequivocal indication of the presence of RW. TW and opposite wood (OW) samples were isolated and subjected to a compression-parallel-to-grain test. It was observed that TW is less resistant and less stiff than the OW. [ABSTRACT FROM AUTHOR]

Pectins are networks of dynamically and variably modified, galacturonan-rich polymers that occur predominantly in the primary cell wall and the middle lamella between cells. Despite their low abundance in lignocellulosic feedstocks, pectins can have outsized, and often negative effects on post-harvest processing. There is compelling evidence that pectins interfere with bio-based saccharification. Transgenic strategies for improving woody biomass utilization by pectin manipulation have therefore been explored. While much research has focused on the apoplastic, in muro steps of pectin modification during cell wall remodelling, recent biotechnological successes suggest potential for substantial and informative gains by targeting biosynthetic steps in the Golgi apparatus. At the same time, it must be recognized that pectins are essential for plant fitness. They comprise a substantial fraction of the primary cell wall, which, during rapid growth and differentiation, constitutes most of the cell wall. Pectin involvement in plant defence, stomatal dynamics, embolism control, root nutrient uptake and trace metal sequestration will also need to be taken into account to maximize the potential for durable gains. Early reports suggest that there is potential for bottom line success, not only for saccharification efficiency, but for biomass yields as well. Longer-term field testing across more varied environments, with more detailed phenotyping, will provide valuable insights for the future of pectin manipulation in woody biomass improvement. [ABSTRACT FROM AUTHOR]

In this research, the effect of tension wood on the roughness of poplar wood in tangential and radial sections was investigated. Steaming at120 ̊C for 30 and 60 min was aslo applied to reduce the roughness. The potential use of roughness measurement technique for macroscopically detection of tension wood was one of the main objectives of this research. Before roughness measurement and for accurate sampling, the detection of tension wood was carried out using Herzberg reagent and microscopic studies. The roughness of samples was measured by stylus profilometer at 12 % moisture content and the surface quality was also studied by stereo-microscope. Results showed that there is no significant difference in the radial and tangential roughness between tension and normal wood. No difference was also observed between the roughness of tangential and radial sections of both types of woods. In contrast, stereo-microscopic studies clearly showed the higher roughness of tension wood. Steaming for 30 min increased the roughness but the treatment for 60 min had a decreasing effect on the roughness of both types of woods. Overall, it can be concluded that the roughness measurement technique cannot be used as a suitable method to nondestructively detect the poplar tension wood.

One-year seedlings of five species of eucalypt: E. camaldulensis, E. microtheca, E. viminalis, E. globulus and E. gunnii were treated for 14 weeks in growth season, tilting a branch to c. 60° in every successful ones. We investigated the anatomical features of stems wood after 15 days and every 2 weeks according to IAWA list of features afterwards.The results showed that tilted stems formed more tension wood in the form of gelatinous fibers than straight (untreated) ones. The formation of gelatinous fibers was considered to be closely related to tension wood formation. The formation of gelatinous fibers was considered to be closely related to tension wood formation. Excluding E. globulus, all the other species formed growth eccentricity and tension wood. Although the significant differences between the species and between different locations in the branches, there were no significant differences between the percent of tension wood among the species studied.

In this research Tension Wood (TW) and Normal Wood (NW) of Poplar were analyzed for pulp production using Kraft pulping process. After preparing samples, Biometric characteristics of the NW and TW fibers were measured and samples were converted to pulp. Pulp hand sheets mechanical and physical properties were measured and results were showed that NW fibers compared to TW fibers had a higher Rankle coefficient and aspect ratio. However the flexibility of NW fibers was better than TW fibers. Based on Results, although TW pulp yield was 13 percent greater than NW pulp yield but kappa number in TW was 45 percent lower than NW. Mechanical and physical properties of hand sheets indicated that the tensile and burst strengths of tension wood were comparatively lower than that of normal wood. Also the papers produced by equally mixture of TW fibers and NW fibers were showed higher tensile and burst strengths. Optical and color analyses of samples were showed an improvement in brightness and whiteness for TW hand sheets compared to NW papers. General speaking results were showed that presence of TW fibers inside pulp had not a significant effect on quality of produced pulp and papers.

* Background and Aims In response to a gravitational stimulus, angiosperm trees generally form tension wood on the upper sides of leaning stems in order to reorientate the stems in the vertical direction. It is unclear whether the angle of inclination from the vertical affects tension wood formation. This study was designed to investigate negative gravitropism, tension wood formation and growth eccentricity in Acacia mangium seedlings inclined at different angles. * Methods Uniform seedlings of A. mangium were artificially inclined at 30°, 45°, 60° and 90° from the vertical and harvested, with non-inclined controls, 3 months later. We analysed the effects of the angle of inclination on the stem recovery angle, the anatomical features of tension wood and radial growth. * Key Results Smaller inclination angles were associated with earlier stem recovery while stems subjected to greater inclination returned to the vertical direction after a longer delay. However, in terms of the speed of negative gravitopism towards the vertical, stems subjected to greater inclination moved more rapidly toward the vertical. There was no significant difference in terms of growth eccentricity among seedlings inclined at different angles. The 30°-inclined seedlings formed the narrowest region of tension wood but there were no significant differences among seedlings inclined at 45°, 60° and 90°. The 90°-inclined seedlings formed thicker gelatinous layers than those in 30°-, 45°- and 60°-inclined seedlings. * Conclusion Our results suggest that the angle of inclination of the stem influences negative gravitropism, the width of the tension wood region and the thickness of gelatinous layers. Larger amounts of gelatinous fibres and thicker gelatinous layers might generate the higher tensile stress required for the higher speed of stem-recovery movement in A. mangium seedlings. [ABSTRACT FROM AUTHOR]

Summary: The phytohormone ethylene impacts secondary stem growth in plants by stimulating cambial activity, xylem development and fiber over vessel formation. We report the effect of ethylene on secondary cell wall formation and the molecular connection between ethylene signaling and wood formation. We applied exogenous ethylene or its precursor 1‐aminocyclopropane‐1‐carboxylic acid (ACC) to wild‐type and ethylene‐insensitive hybrid aspen trees (Populus tremula × tremuloides) and studied secondary cell wall anatomy, chemistry and ultrastructure. We furthermore analyzed the transcriptome (RNA Seq) after ACC application to wild‐type and ethylene‐insensitive trees. We demonstrate that ACC and ethylene induce gelatinous layers (G‐layers) and alter the fiber cell wall cellulose microfibril angle. G‐layers are tertiary wall layers rich in cellulose, typically found in tension wood of aspen trees. A vast majority of transcripts affected by ACC are downstream of ethylene perception and include a large number of transcription factors (TFs). Motif‐analyses reveal potential connections between ethylene TFs (Ethylene Response Factors (ERFs), ETHYLENE INSENSITIVE 3/ETHYLENE INSENSITIVE3‐LIKE1 (EIN3/EIL1)) and wood formation. G‐layer formation upon ethylene application suggests that the increase in ethylene biosynthesis observed during tension wood formation is important for its formation. Ethylene‐regulated TFs of the ERF and EIN3/EIL1 type could transmit the ethylene signal. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Dimensions and spatial distribution of vessels are critically important features of woody stems, allowing for adaptation to different environments through their effects on hydraulic efficiency and vulnerability to embolism. Although our understanding of vessel development is poor, basipetal transport of auxin through the cambial zone may play an important role. METHODS: Stems of Populus tremula x alba were treated with the auxin transport inhibitor N-1- naphthylphthalamic acid (NPA) in a longitudinal strip along the length of the lower stem. Vessel lumen diameter, circularity and length; xylem growth; tension wood area and hydraulic conductivity before and after a high pressure flush were determined on both NPA-treated and control plants. KEY RESULTS: NPA-treated stems formed aberrant vessels that were short, small in diameter, highly clustered and angular in cross section, whereas xylem formed on the untreated side of the stem contained typical vessels that were similar to those of controls. NPA-treated stems had reduced specific conductivity relative to controls, but this difference was eliminated by the high-pressure flush. The control treatment (lanolin + dimethyl sulfoxide) reduced xylem growth and increased tension wood formation, but never produced the aberrant vessel patterning seen in NPA-treated stems. CONCLUSIONS: These results are consistent with a model of vessel development in which basipetal polar auxin transport through the xylem-side cambial derivatives is required for proper expansion and patterning of vessels and demonstrate that reduced auxin transport can produce stems with altered stem hydraulic properties. [ABSTRACT FROM AUTHOR]