Showing papers by "Masato Yoshida published in 2016"

Distribution of coniferin in freeze-fixed stem of Ginkgo biloba L. by cryo-TOF-SIMS/SEM.

Abstract: To clarify the role of coniferin in planta, semi-quantitative cellular distribution of coniferin in quick-frozen Ginkgo biloba L. (ginkgo) was visualized by cryo time-of-flight secondary ion mass spectrometry and scanning electron microscopy (cryo-TOF-SIMS/SEM) analysis. The amount and rough distribution of coniferin were confirmed through quantitative chromatography measurement using serial tangential sections of the freeze-fixed ginkgo stem. The lignification stage of the sample was estimated using microscopic observations. Coniferin distribution visualized at the transverse and radial surfaces of freeze-fixed ginkgo stem suggested that coniferin is stored in the vacuoles, and showed good agreement with the assimilation timing of coniferin to lignin in differentiating xylem. Consequently, it is suggested that coniferin is stored in the tracheid cells of differentiating xylem and is a lignin precursor.

Lignification of ray parenchyma cells (RPCs) in the xylem of Phellodendron amurense Rupr.: quantitative and structural investigation by TOF-SIMS and thioacidolysis of laser microdissection cuts of RPCs

Abstract: Abstract Lignification of ray parenchyma cells (RPCs) in the sapwood (sW), transition zone (TZ), and heartwood (hW) of Phellodendron amurense Rupr. has been investigated by time-of-flight secondary ion mass spectrometry (TOF-SIMS) and thioacidolysis. The results of TOF-SIMS indicate that the relative ion intensity of lignin in RPCs increased from sW to hW, while there was almost no difference in the case of axial wood fibers. The ratio of syringyl (S) to guaiacyl (G) lignin units (S/G value) in RPCs was higher than that in wood fibers. Samples containing more RPCs were prepared by laser microdissection (LMD) and analyzed by thioacidolysis, including also the subsequent Raney nickel desulfurization, and the resulting monomers and dimers were quantitatively analyzed by GC/MS. The monomer analysis shows that lignin content and S/G values in RPCs rich samples increased from sW towards hW. The dimer analysis reveals that the S-S dimers are dominant in all types of samples. The results of TOF-SIMS and thioacidolysis of LMD samples are interpreted that the lignification of RPCs progresses from the sW towards the hW and that the chemical structure of lignin in RPCs is different from that in axial elements.

Effect of hygrothermal treatment on wood properties: color changes and kinetic analysis using four softwood and seven hardwood species

Abstract: Color changes of four softwood and seven hardwood species during hygrothermal treatment were compared among species and kinetically evaluated. Treatment temperature ranged from 70 to 120 °C, and the durations were 5–150 h. Generally, the $$L^{*}$$ (lightness) decreased and the total color differences $$(\Delta E_{\text{ab}}^{*})$$ increased irrespective of the treatment temperature. $$a^{*}$$ and $$b^{*}$$ (redness and yellowness) values varied spuriously based on the wood species. Kinetic analysis using the time–temperature superposition principle, which uses the whole data set, was successfully applied to the color changes. The apparent activation energies of the color changes calculated from $$\Delta E_{\text{ab}}^{*}$$ were 24.3–40.8 kJ/mol for softwood and 32.3–61.3 kJ/mol for hardwood. The average apparent activation energy for hardwood was higher than for softwood. These values were lower than those calculated from other material properties. The obtained results will contribute to assess the color changes during the early stage of kiln drying and hygrothermal modification of wood.

Negative gravitropism of Ginkgo biloba: growth stress and reaction wood formation

Abstract: Abstract Ginkgo (Ginkgo biloba L.) forms thick, lignified secondary xylem in the cylindrical stem as in Pinales (commonly called conifers), although it has more phylogenetic affinity to Cycadales than to conifers. Ginkgo forms compression wood-like (CW-like) reaction wood (RW) in its inclined stem as it is the case in conifers. However, the distribution of growth stress is not yet investigated in the RW of ginkgo, and thus this tissue resulting from negative gravitropism is still waiting for closer consideration. The present study intended to fill this gap. It has been demonstrated that, indeed, ginkgo forms RW tissue on the lower side of the inclined stem, where the compressive growth stress (CGS) was generated. In the RW, the micorofibril angle in the S2 layer, the air-dried density, and the lignin content increased, whereas the cellulose content decreased. These data are quite similar to those of conifer CWs. The multiple linear regression analysis revealed that the CGS is significantly correlated by the changes in the aforementioned parameters. It can be safely concluded that the negative gravitropism of ginkgo is very similar to that of conifers.

Hygrothermal recovery of compression wood in relation to elastic growth stress and its physicochemical characteristics

Abstract: Hygrothermal recovery (HTR), the dimensional changes in wood induced by hygrothermal treatment, was investigated using both compression and normal wood of sugi (Cryptomeria japonica). The elastic released strain of growth stress was measured on living tree surfaces; subsequently, the specimens were taken from the same position to measure HTR. HTR was measured as dimensional changes due to treatment at 20, 40, 60, 80, and 100 °C in hot water ranging from 200 min to 177 days. The intensity of HTR had a positive relationship with elastic released strain of growth stress. This result suggests that HTR is the relaxation of the viscoelastic component of growth stress accumulated during the maturation process of trees. The rate of HTR clearly showed a time–temperature dependency: higher at higher treatment temperatures and lower at lower treatment temperatures. Based on kinetic analysis, the apparent activation energy (E a) was calculated as 407 kJ/mol, which is similar to the published E a of lignin softening implying that the HTR is a lignin-related phenomenon.

Is hygrothermal recovery of tension wood temperature-dependent?

Abstract: When a green wood specimen is hygrothermally treated, it often shows dimensional changes in the longitudinal and transversal directions, which is called hygrothermal recovery of wood. Hygrothermal recovery of tension wood is assumed to be behind the unusual contraction of gelatinous layer along the longitudinal axis. This study investigated whether hygrothermal recovery of tension wood was temperature-dependent. Hygrothermal treatment at 80, 100 and 120 °C was given to green Quercus serrata tension wood, and longitudinal and tangential dimensions were recorded. In the longitudinal direction, the trend line obtained after 10 times of 10-min hygrothermal treatments at respective temperatures unraveled that it was comprised of initial recovery and continuum contraction at 100 and 120 °C, but no initial recovery was recognized at 80 °C. In the tangential direction, both the initial and the continuum deformations were expansive, and initial recovery was smaller at 80 °C. The results of multiple comparison test revealed that the parameters characterizing the trend line differed significantly among three temperature sets. Further, the result highlighted the existence of breakage of hygrothermal recovery mechanism at temperature between 80 and 100 °C.

In situ detection of laccase activity and immunolocalisation of a compression-wood-specific laccase (CoLac1) in differentiating xylem of Chamaecyparis obtusa.

Abstract: The secondary cell wall of compression wood tracheids has a highly lignified region (S2L) in its outermost portion. To better understand the mechanism of S2L formation, we focussed on the activity of laccase (a monolignol oxidase) and performed in situ studies of this enzyme in differentiating compression wood. Staining of differentiating compression wood demonstrated that laccase activity began in all cell wall layers before the onset of lignification. We detected no activity of peroxidase (another monolignol oxidase) in any cell wall layer. Thus, laccase likely plays the major role in monolignol oxidisation during compression wood differentiation. Laccase activity was higher in the S2L region than in other secondary wall regions, suggesting that this enzyme was responsible for the high lignin concentration in this region of the cell wall. Immunolabelling demonstrated the expression of a compression-wood-specific laccase (CoLac1) immediately following the onset of secondary wall thickening, this enzyme was localised to the S2L region, whereas much less abundant in the S1 layer or inner S2 layer. Thus, the CoLac1 protein is most likely localised to the outer part of S2 and responsible for the high lignin concentration in the S2L region.

Common Mechanism of Lignification of Compression Wood in Conifers and Buxus

Abstract: Woody plants develop a specialized secondary xylem known as reaction wood to enable formation of an ideal shape Reaction wood in coniferous species is known as compression wood, and that of woody angiosperms as tension wood However, the genus Buxus which is classified as an angiosperm, forms compression-wood-like reaction wood We investigated the mechanism of lignification in coniferous compression wood and Buxus reaction wood: 1) Several lignin synthesis genes were upregulated in differentiating reaction wood of Buxus microphylla; 2) B microphylla possesses a specific laccase gene that is expressed specifically in differentiating reaction wood (BmLac4); 3) laccase activity localization was closely related to lignification of reaction wood, and laccase activity was high in the secondary wall middle layer; 4) in reaction wood cell walls, galactan was present in the outer portion of the secondary wall middle layer, and the level of xylan was reduced These findings suggest that lignification in B microphylla reaction wood is identical to that of coniferous compression wood These may represent general mechanisms of increasing lignin content in various reaction woods

Observations of Wood Cell Walls with a Scanning Probe Microscope

Abstract: Scanning Probe Microscopes (SPMs) observe specimen surfaces with probes by detecting the physical amount of a material between the cantilever and the surface. SPMs have a high resolution and can measure mechanical characteristics such as stiffness, adsorptive properties, and viscoelasticity. These features make it easy to identify the surface structure of complex materials; therefore, the use of SPMs has increased in recent years. Wood cell walls are primarily composed of cellulose, hemicellulose, and lignin. It is believed that hemicellulose and lignin surround the cellulose framework; however, their detailed formation remains unknown. Therefore, we observed wood cell walls via scanning probe microscopy to try to reveal the formation of the cellulose framework. We determined that the size of the cellulose microfibril bundle and hemicellulose lignin module composite was 18.48 nm based on topography and that the size of the cellulose microfibril bundle was 15.33 nm based on phase images. In the viscoelasticity image, we found that the viscoelasticities of each cell wall of the same cell were not the same. This is because the cellulose microfibrils in each cell wall lean in different directions. The angle between the leaning of the cellulose microfibril and the cantilever affects the viscoelasticity measurement.

Diurnal Periodicity of the Expression of Genes Involved in Monolignol Biosynthesis in Differentiating Xylem of Cryptomeria japonica

Abstract: The cell wall in wood is mainly composed of three components: cellulose, hemicellulose and lignin. According to electron microscopy observations of the innermost surface of cell walls in the tracheids of Cryptomeria japonica , cellulose microfibrils are deposited during the day and a matrix containing hemicellulose is deposited at night. This indicates that the deposition of cell wall components exhibits diurnal periodicity. To gain new insights into the diurnal periodicity of lignin deposition not revealed by microscopic observations, we examined diurnal fluctuations in the expression of genes involved in monolignol biosynthesis in C. japonica saplings grown in the field and in growth chambers under a 12 h light/dark cycle. In the field experiment, two gene expression peaks were observed daily, at dusk and dawn. In the growth chamber experiment, two daily peaks were observed 0 h and 6 - 9 h after the light switched on.