Showing papers by "Masato Yoshida published in 2006"

Diurnal differences in the supply of glucomannans and xylans to innermost surface of cell walls at various developmental stages from cambium to mature xylem in Cryptomeria japonica.

Abstract: We investigated the diurnal differences in the innermost surface of tracheid cell walls at various developmental stages from cambium to mature xylem. Cryptomeria japonica saplings were cultivated in a growth chamber with a light cycle set at 14 h of light and 10 h of darkness. Samples were collected from the saplings during both the light and dark periods. The innermost surface of cell walls was immunogold-labeled with anti-glucomannan or anti-xylan antiserum and was observed by field emission scanning electron microscopy. Diurnal differences in the aspect of the innermost surface of cell walls were seen only in S2-layer-forming tracheids; cellulose microfibrils were clearly evident during the light period, and amorphous material containing glucomannans and xylans was prevalent during the dark period. Cellulose microfibrils were present at the primary-wall formation and S1-layer-forming stages, and many warts were observed in the mature tracheids, regardless of the time of sampling. The densities of labeled glucomannans on the innermost surface of cell walls in S1- and S2-forming tracheids and of labeled xylans in S2-forming tracheids during the dark period were significantly higher than those during the light period. These results suggest a diurnal periodicity in the supply of cell wall matrix containing hemicellulose to the innermost surface of developing secondary walls.

Strains inside xylem and inner bark of a stem submitted to a change in hydrostatic pressure

Abstract: Tangential strains were measured with strain gauges at the surface of xylem and inner bark of saplings of Cryptomeria japonica D. Don. and Fagus silvatica L. during a pressurization test. The test consists in submitting the whole sapling to an artificially imposed hydrostatic pressure of increasing magnitude. The elastic response of the stems was found linear both at the surface of xylem and inner bark. A simple geometric model allows to compute radial strains in each tissue from tangential strain data. Inside inner bark, radial strains are much larger than tangential strains, because tangential strains are restrained by the core of wood. The material compliance of each tissue was computed as the ratio between the radial strain and the pressure that caused it. The material compliance of xylem is much lower than that of inner bark, but, as its thickness is much larger, its contribution to the apparent behavior of the stem is not negligible. Computation of material compliances by this pressurization test provides information about the specific behavior of each tissue in response to hydrostatic pressure. This can be used to estimate and interpret the calibration factor linking the water status of the plant to the apparent strain measured at its surface.

The generation of longitudinal maturation stress in wood is not dependent on diurnal changes in diameter of trunk

Abstract: A hypothetical mechanism for the generation of maturation stress in wood was tested experimentally. The hypothesis was that the maturation stress could partly originate in a physical mechanism related to daily changes in water pressure and associated diurnal strains. The matrix of lignin and hemicellulose, deposited in the cell wall during the night, would be put in compression by the effect of water tension during the next day. The cellulose framework, crystallizing during the day, would be put in tension by the decrease in tension at night and subsequent cell-wall swelling. This was tested on young saplings of sugi and beech. Half of the saplings were submitted to continuous lighting, which canceled diurnal strains. Saplings were tilted 40 degrees, and their uprighting movement was measured. The uprighting movement is directly due to the production of reaction wood and the concomitant development of large longitudinal maturation stress. It occurred in the continuously lighted plants at least as much as in control plants. We conclude that the generation of longitudinal maturation stress in tension or compression wood is not directly related to variations in water pressure and diurnal strains.

The supply of matrix containing glucomannans to the innermost surface of S2 layers is associated with changes in turgor pressure of differentiating tracheids in Cryptomeria japonica

Abstract: We investigated the relationship between turgor pressure and diurnal differences in secondary wall formation of differentiating tracheids. Saplings of Cryptomeria japonica were grown in a growth chamber with 12-h light:12-h dark cycles, and the tangential strain on the inner bark surface was measured as an indicator of the volumetric changes of differentiating cells. The innermost surface of developing secondary walls was then observed using field emission scanning electron microscopy at 1-h intervals after both light and dark periods. Dramatic changes in the aspects of the innermost surface of developing secondary walls occurred 3h after the light was switched on and 4h after the light was switched off. The amorphous material containing glucomannans became evident when the differentiating cells became fully turgid during the dark period. Conversely, cellulose microfibrils became clearly visible when the cell volume was low during the light period. These results suggest that the diurnal periodicity in the supply of hemicellulose-containing matrix to developing secondary walls is associated with the changes in turgor pressure of differentiating tracheids that result from the change in light conditions during the photoperiodic cycle.

Ultrastructure of lignified plant cell wall observed by field-emission scanninng electron microscopy. observations on periodate lignin prepared from ginkgo biloba

Abstract: To obtain information on the ultrastructural assembly of lignin and polysaccharides in the cell wall, the polysaccharides were selectively removed by periodate oxidation from the differentiating ginkgo xylem, to give periodate lignin, to be subsequently analyzed by high resolution FE-SEM (field-emission scanning electron microscopy). In the lignifying cell wall, lignin is formed as bead-like modules of the lignin-polysaccharide complex surrounding the cellulose microfibrils. The growing modules are fused together to form high molecular aggregates, to fill" up the space between the cellulose microfibrils. The periodate lignin composed of fused lignin modules retained the morphological features of the original cell wall structure, although some shrinkage occurred, as a result of polysaccharides removal. The observations provided useful information on the heterogeneous distribution of the condensed lignin substructures, with respect to the cell wall layers, and also on the ultrastructural assembly of lignin and polysaccharides in ginkgo tracheids.

Measurement of residual strains at stem periphery using the two-grooves method

Abstract: The two grooves method commonly used for measuring residual growth strains at tree stem surface has been analysed through finite elements simulations. The effect of groove depth and distance between gauge and groove are qualitatively similar to previously published experimental findings, but a strong effect of the stem radius can be observed. Simulations show that for too small groove depth and gauge length the residual strain value would be considerably underestimated. Further analysis should take better account of localised non-linear deformation processes.