Ethylene signaling induces gelatinous layers with typical features of tension wood in hybrid aspen.

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.

On radiation damage in FIB-prepared softwood samples measured by scanning X-ray diffraction.

The high flux density encountered in scanning X-ray nanodiffraction experiments can lead to severe radiation damage to biological samples. However, this technique is a suitable tool for investigating samples to high spatial resolution. The layered cell wall structure of softwood tracheids is an interesting system which has been extensively studied using this method. The tracheid cell has a complex geometry, which requires the sample to be prepared by cutting it perpendicularly to the cell wall axis. Focused ion beam (FIB) milling in combination with scanning electron microscopy allows precise alignment and cutting without splintering. Here, results of a scanning X-ray diffraction experiment performed on a biological sample prepared with a focused ion beam of gallium atoms are reported for the first time. It is shown that samples prepared and measured in this way suffer from the incorporation of gallium atoms up to a surprisingly large depth of 1 µm.

Synchrotron X-ray micro-tomography imaging and analysis of wood degraded by Physisporinus vitreus and Xylaria longipes.

Incubation of Norway spruce with Physisporinus vitreus and sycamore with Xylaria longipes results in reduction in density of these wood species that are traditionally used for the top and bottom plate of a violin, which follows by enhanced acoustic properties. We used Synchrotron X-ray micro-tomography, to study the three-dimensional structure of wood at the micro-scale level and the alterations of the density distribution after incubation with two white-rot fungi. Micro-tomography data from wood treated at different incubation periods are analyzed and compared with untreated (control) specimens to determine the wood density map and changes at the cell-wall level. Differences between the density of early- and latewood, xylem ray and around bordered pits in both Norway spruce and sycamore are studied. Three-dimensional hyphal networks of the P.vitreus and Xylaria longipes hyphae are visualized inside the cell lumina and their significance on the density of the early- and latewood cells after different incubation periods are discussed. The study illustrates the utility of X-ray micro-tomography for both qualitative and quantitative studies of a wide variety of biological systems and due to its high sensitivity, small structural changes can be quantified.

[Investigation of characteristic microstructures of adhesive interface in wood/bamboo composite material by synchrotron radiation X-ray phase contrast microscopy].

Third-generation synchrotron radiation X-ray phase-contrast microscopy(XPCM)can be used for obtaining image with edge enhancement, and achieve the high contrast imaging of low-Z materials with the spatial coherence peculiarity of X-rays. In the present paper, the characteristic microstructures of adhesive at the interface and their penetration in wood/bamboo composite material were investigated systematically by XPCM at Shanghai Synchrotron Radiation Facility (SSRF). And the effect of several processing techniques was analyzed for the adhesive penetration in wood/bamboo materials. The results show that the synchrotron radiation XPCM is expected to be one of the important precision detection methods for wood-based panels.

Parámetros micrográficos para la identificación de leño, corteza y hoja de Quassia amara L. (Simaroubaceae) / Micrographic parameters for identification of Quassia amara L., wood, bark and leaf

Quassia amara L. popularly known as “quasia”, is a shrubby plant from Tropical America. The wood, bark and leave are used in either folk medicine or in procuring phytotherapeutic drugs. The aim of the present work was to analize morphoanatomical and micrographic features which might provide assistance in the identification, analysis and standardization of Quasia amara L wood, bark and leaves. Results. Anatomical study showed white yellowish and diffuse porous wood, confluent paratracheal parenchyma. Rays width 1 cell wide and 8-30 cells high. CaOx crystals are absent. Cortex, 1-4 mm thick, a periderm up to 12 layers phellem cells. Leaf, hipostomatic with dorsiventral mesophyll and high number of sclerosed idioblasts.

Quassia amara L. popularmente conocida como “quasia” es un planta arbustiva de América Tropical. El leño, corteza y hojas son usadas tanto en medicina popular como en la obtención de drogas fitoterapéuticas. El objetivo del presente trabajo es analizar características morfoanatómicas y micrográficas las cuales provean asistencia en la identificación, análisis y estandarización de la madera, corteza y hojas de Quassia amara L. Resultados. El estudio anatómico mostró leño, blanco amarillento, de porosidad difusa. Parénquima paratraqueal confluente. Radios de 1 célula de ancho y 8-30 hileras de alto. Faltan cristales CaOx. Corteza, 1-4 mm de espesor, una peridermis de hasta 12 estratos de células de súber. Hoja, hipoestomática, con mesófilo dorsiventral, con elevado número de idioblastos esclerosados.

Computer-assisted scanning electron microscopy of wood pulp fibres: dimensions and spatial distributions in a polypropylene composite.

A shape description approach is introduced as a step for performing an automatic processing of fibre cross-sectional images. The approach, in combination with appropriate mathematical morphology, yields edited images, which are suitable for further computerized image analysis. Important parameters such as fibre wall thickness, fibre perimeter, form factor and collapse index are quantified effectively and objectively. Although some differences are encountered within groups of split fibres, manual and automatic quantification of intact fibres yields similar results. In addition, the suitability of a distance transform approach for quantifying the fibre inter-distances in composites is demonstrated. Such tools will be valuable for understanding the mechanical properties of engineered fibre-reinforced composite materials.