Intra-annual fluctuation in morphology and microfibril angle of tracheids revealed by novel microscopy-based imaging

Woody cells, such as tracheids, fibers, vessels, rays etc., have unique structural characteristics such as nano-scale ultrastructure represented by multilayers, microfibril angle (MFA), micro-scale anatomical properties and spatial arrangement. Simultaneous evaluation of the above indices is very important for their adequate quantification and extracting the effects of external stimuli from them. However, it is difficult in general to achieve the above only by traditional methodologies. To overcome the above point, a new methodological framework combining polarization optical microscopy, fluorescence microscopy, and image segmentation is proposed. The framework was tested to a model softwood species, Chamaecyparis obtusa for characterizing intra-annual transition of MFA and tracheid morphology in a radial file unit. According our result, this framework successfully traced the both characteristics tracheid by tracheid and revealed the high correlation (|r| > 0.5) between S2 microfibril angles and tracheidal morphology (lumen radial diameter, tangential wall thickness and cell wall occupancy). In addition, radial file based evaluation firstly revealed their complex transitional behavior in transition and latewood. The proposed framework has great potential as one of the unique tools to provide detailed insights into heterogeneity of intra and inter-cells in the wide field of view through the simultaneous evaluation of cells’ ultrastructure and morphological properties

Flexural behavior of wood in the transverse direction investigated using novel computer vision and machine learning approach

A deep-learning-based semantic segmentation approach (U-Net) was used to partition the anatomical features in the cross-section of hinoki (Chamaecyparis obtusa) wood during a micro three-point bending test. Using the Crocker–Grier linking algorithm, thousands of cells were successfully extracted, and several parameters (area, eccentricity, fitted ellipse aspect ratio, bounding box aspect ratio) were used to evaluate the intensity of the cells’ deformation. Thus, the 2D map of the deformation intensity distribution was constructed. By analyzing flat-sawn, quarter-sawn, and rift-sawn specimens, it was confirmed that the annual ring orientation affects the flexural behavior of wood in the transverse direction. The quarter-sawn specimens exhibited the largest modulus of elasticity (MOE) and modulus of rupture (MOR). The ray tissue aligned against the load may have contributed to the restriction of cell deformation. The rift-sawn specimens exhibited the smallest MOE and MOR, possibly owing to the loading of the specimen in the in-plane off-axial direction, which induced the shear deformation of the cell wall. For all three specimen types, the fracture had high occurrence probability in the tension part of the specimen, which exhibited large cell deformation. Therefore, the proposed method can be adapted to the prediction of wood specimen fractures. With different test wood species, this approach can be of great help in elucidating the relationship between the anatomical features and the mechanical behavior of wood to improve the effective utilization of wood resources

Synthesis of diblock copolymers with cellulose derivatives 4. Self-assembled nanoparticles of amphiphilic cellulose derivatives carrying a single pyrene group at the reducing-end

Self-assembled cellulose-pyrene nanoparticles were prepared from amphiphilic cellulose derivatives carrying a single pyrene group at the reducing-end, N-(1-pyrenebutyloyl)-β-cellulosylamine (CELL13Py and CELL30Py, the number average degrees of polymerization (DPn) of 13 and 30, respectively) and N-(15-(1-pyrenebutyloylamino)-pentadecanoyl)-β-cellulosylamine (CELL13C15Py and CELL30C15Py, DPn of 13 and 30, respectively). Transmission electron microscopy (TEM) observation revealed that CELL13C15Py and CELL30C15Py formed self-assembled nanoparticles with the average diameters of 108.8 and 40.0 nm, respectively. The average radius of CELL30C15Py nanoparticles (20.0 nm) agreed well with the molecular length of its cellulose chain (19.2 nm). CELL30C15Py nanoparticles were expected to have monolayered structure, consisting of cellulose shell with radial orientation and hydrophobic core of 15-(1-pyrenebutyloylamino)-pentadecanoyl groups. The fluorescent spectrum of CELL30C15Py nanoparticles showed an excimer emission due to dimerized pyrene groups, indicating that the pyrene groups at the reducing-end of cellulose are associating in the particles. The balance of hydrophilic and hydrophobic parts of the cellulose derivatives controlled their self-assembled nanostructures. X-ray diffraction measurements revealed that radially oriented cellulose chains of CELL30C15Py nanoparticles were mostly amorphous, and at the same time exhibited weak reflection pattern of cellulose II, which is believed to have anti-parallel orientation

Potential of machine learning approaches for predicting mechanical properties of spruce wood in the transverse direction

To predict the mechanical properties of wood in the transverse direction, this study used machine learning to extract the anatomical features of wood from cross-sectional stereograms. Specimens with different orientations of the ray parenchyma cell were prepared, and their modulus of elasticity (MOE) and modulus of rupture (MOR) were measured by a three-point bending test. The orientation of the ray parenchyma cell and wood density (ρ) were used as parameters for the MOE and MOR prediction. Conventional machine learning algorithms and artificial neural network were used, and satisfactory results were obtained in both cases. A regular convolutional neural network (CNN) and a density-informed CNN were used to automatically extract anatomical features from the specimens’ cross-sectional stereograms to predict the mechanical properties. The regular CNN achieved acceptable but relatively low accuracy in both the MOE and MOR prediction. The reason for this may be that ρ information could not be satisfactorily extracted from the images, because the images represented a limited region of the specimen. For the density-informed CNN, the average prediction coefficient for both the MOE and MOR drastically increased when ρ information was provided. A regression activation map was constructed to understand the representative anatomical features that are strongly related to the prediction of mechanical properties. For the regular CNN, the latewood region was highly activated in both the MOE and MOR prediction. It is believed that the ratio and orientation of latewood were successfully extracted for the prediction of the considered mechanical properties. For the density-informed CNN, the activated region is different. The earlywood region was activated in the MOE prediction, while the transition region between the earlywood and latewood was activated in the MOR prediction. These results may provide new insights into the relationship between the anatomical features and mechanical properties of wood

Multilayered Structure of Tension Wood Cell Walls in Salicaceae \u3ci\u3esensu lato\u3c/i\u3e and Its Taxonomic Significance

Salicaceae have been enlarged to include a majority of the species formerly placed in the polyphyletic tropical Flacourtiaceae. Several studies have reported a peculiar and infrequently formed multilayered structure of tension wood in four of the tropical genera. Tension wood is a tissue produced by trees to restore their vertical orientation and most studies have focused on trees developing tension wood by means of cellulose-rich, gelatinous fibres, as in Populus and Salix (Salicaceae s.s.). This study aims to determine if the multilayered structure of tension wood is an anatomical characteristic common in other Salicaceae and, if so, how its distribution correlates to phylogenetic relationships. Therefore, we studied the tension wood of 14 genera of Salicaceae and two genera of Achariaceae, one genus of Goupiaceae and one genus of Lacistemataceae, families closely related to Salicaceae or formerly placed in Flacourtiaceae. Opposite wood and tension wood were compared with light microscopy and three-dimensional laser scanning confocal microscopy. The results indicate that a multilayered structure of tension wood is common in the family except in Salix, Populus and one of their closest relatives, Idesia polycarpa. We suggest that tension wood may be a useful anatomical character in understanding phylogenetic relationships in Salicaceae. Further investigation is still needed on the tension wood of several other putatively close relatives of Salix and Populus, in particular Bennettiodendron, Macrohasseltia and Itoa

Localized laccase activity modulates distribution of lignin polymers in gymnosperm compression wood

The woody stems of coniferous gymnosperms produce specialised compression wood to adjust the stem growth orientation in response to gravitropic stimulation. During this process, tracheids develop a compression-wood-specific S2L cell wall layer with lignins highly enriched with p-hydroxyphenyl (H)-type units derived from H-type monolignol, whereas lignins produced in the cell walls of normal wood tracheids are exclusively composed of guaiacyl (G)-type units from G-type monolignol with a trace amount of H-type units. We show that laccases, a class of lignin polymerisation enzymes, play a crucial role in the spatially organised polymerisation of H-type and G-type monolignols during compression wood formation in Japanese cypress (Chamaecyparis obtusa). We performed a series of chemical-probe-aided imaging analysis on C. obtusa compression wood cell walls, together with gene expression, protein localisation and enzymatic assays of C. obtusa laccases. Our data indicated that CoLac1 and CoLac3 with differential oxidation activities towards H-type and G-type monolignols were precisely localised to distinct cell wall layers in which H-type and G-type lignin units were preferentially produced during the development of compression wood tracheids. We propose that, not only the spatial localisation of laccases, but also their biochemical characteristics dictate the spatial patterning of lignin polymerisation in gymnosperm compression wood

Water-soluble low-molecular-weight cellulose chains radially oriented on gold nanoparticles

Cellulose chains bearing N-lipoyl group at the reducing-end as a sulfide linker, self-assembled on the surface of gold nanoparticles (CELL2Au, CELL13Au, and CELL41Au with the number average degrees of polymerization (DPn) of 2, 13, and 41, respectively) were prepared. CELL2Au, CELL13Au, and CELL41Au were obtained via deprotection of the cellulose triacetate (CTA) self-assembled on the surface of gold nanoparticles that are consisting of CTA chains with corresponding DPn organized in a radial manner with head-to-tail orientation, where a head is the reducing-end, and a tail is the non-reducing-end. CELL2Au and CELL13Au were well-dispersed in water including a trace of methanol, whereas CELL41Au was not. The transmission electron microscopy (TEM) observation of CELLAus deposited on copper grids revealed that the diameters (d) of the gold cores of CELL2Au, CELL13Au, and CELL41Au were 6.1, 6.1, and 11.5 nm, respectively. Wide angle X-ray diffractgram showed that cellulose chains of CELL13Au had quite low crystallinity and exhibited additional faint diffraction pattern of cellulose II. Cellulose chains of CELL41Au were amorphous. The UV–vis measurements revealed that CELL2Au and CELL13Au were well-dispersed in water. The hydrodynamic diameters (D) of CELL2Au and CELL13Au in water were 21.8 and 55.9 nm, respectively, according to dynamic light scattering (DLS) measurements, suggesting that cellulose chains on the gold were organized in a radial manner with head-to-tail orientation. 1H-NMR measurement revealed that low-molecular-weight cellulose chains (DPn = 13) on the gold dissolved in water, whereas low-molecular-weight cellulose (DPn = 13) itself did not

Methylcelluloses end-functionalized with peptides as thermoresponsive supramolecular hydrogelators

This paper describes the synthesis of methylcelluloses end-functionalized with peptides and an investigation into their functions. We found that aqueous solutions of methylcellulose end-functionalized not only with carbohydrates but also with peptide segments, such as di(arginine) and di(glutamic acid), behave as thermoresponsive supramolecular hydrogelators at human-body temperature. The slow drug release from thermoresponsive hydrogels of methylcelluloses end-functionalized with peptides is attributed to ionic interactions between model drugs and peptide segments in these hydrogels. Reactions of methylated cellobiose with di(arginine) and di(glutamic acid) were used to determine optimum reaction conditions for the synthesis of methylcelluloses end-functionalized with these peptide residues). The surface activities, zeta potentials, thermal properties, hydrogelation behavior, and cytotoxicities of these peptide-functionalized methylcelluloses are also discussed