Microfibril Angles Inside and Outside Crossfields of Norway Spruce Tracheids

Holzforschung ◽  
2003 ◽  
Vol 57 (1) ◽  
pp. 13-20 ◽  
Author(s):  
H. C. Lichtenegger ◽  
M. Müller ◽  
R. Wimmer ◽  
P. Fratzl
Keyword(s):  
Norway Spruce ◽  
Cell Walls ◽  
Mechanical Stability ◽  
Microfibril Angle ◽  
Adjacent Cell ◽  
Cell Axis ◽  
X Ray ◽  
Cellulose Fibrils ◽  
Weak Points ◽  
Ray Parenchyma Cells

Summary The major part of the wood cell wall consists of parallel-aligned cellulose fibrils. Locally, pits connecting adjacent cell walls disturb the fibril arrangement. The local fibril orientation around these mechanically weak points is crucial for the mechanical stability of the cell. In some softwood species like spruce, the pit apertures at junctions of tracheids and cross-running ray parenchyma cells are elongated and slit-like. The pit orientation has often been assumed to directly reflect the fibril orientation. In this paper we use X-ray microdiffraction to determine the local microfibril angle (tilt angle versus the cell axis, MFA) in single tracheid walls of Norway spruce in the vicinity of pit apertures. The results from microdiffraction are compared with the pit orientation observed under the light microscope.Whereas a good correlation was found in thick-walled latewood cells from the stem and compression wood, large discrepancies occurred for thin-walled earlywood cells. A simple mechanical model that could explain the different situation in earlywood and latewood is presented.

Imaging of the helical arrangement of cellulose fibrils in wood by synchrotron X-ray microdiffraction

1999 ◽  
Vol 32 (6) ◽  
pp. 1127-1133 ◽  
Author(s):  
H. Lichtenegger ◽  
M. Müller ◽  
O. Paris ◽  
Ch. Riekel ◽  
P. Fratzl
Keyword(s):  
Incident Beam ◽  
Special Choice ◽  
Local Orientation ◽  
Cell Axis ◽  
Beam Position ◽  
X Ray ◽  
Diffraction Geometry ◽  
Ewald Sphere ◽  
Cellulose Fibrils ◽  
Diffraction Patterns

A complete image of the helical arrangement of cellulose fibrils in the S2 layer of adjacent wood cells ofPicea abies(Norwegian spruce) was obtained by applying position-resolved synchrotron X-ray microdiffraction on cells in cross section. In contrast to conventional fiber diffraction studies, the incident beam was parallel to the longitudinal cell axis, resulting in a glancing angle μ far from 90° with respect to the cellulose fibrils. This special choice of diffraction geometry allowed us to take advantage of an asymmetry effect in the two-dimensional diffraction patterns arising from the curvature of the Ewald sphere to obtain information on the local orientation of the cellulose fibrils. The small size of the beam, smaller than the thickness of a single cell wall, allowed mesh scans over intact transverse sections of adjacent wood cells with a microscopic position resolution. The scan yielded a map of diffraction patterns that could readily serve as a microscopic image. Each of the diffraction patterns was then used to evaluate the local orientation of the cellulose fibrils at the actual beam position. The combination of these results gave an image of cellulose fibrils forming (Z) helices in several adjacent wood cells.

scholarly journals The derivation of the cellulose microfibril angle by small-angle X-ray scattering from structurally characterized softwood cell-wall populations

2005 ◽  
Vol 38 (3) ◽  
pp. 505-511 ◽  
Author(s):  
Kenneth M. Entwistle ◽  
Stephen J. Eichhorn ◽  
Namasivayam Navaranjan
Keyword(s):  
Cell Wall ◽  
Standard Deviation ◽  
Intensity Distribution ◽  
Cell Walls ◽  
Radial Direction ◽  
Microfibril Angle ◽  
Scattered Intensity ◽  
X Ray ◽  
The Real ◽  
X Ray Scattering

A method is presented for the measurement, using small-angle X-ray scattering (SAXS), of the microfibril angle and the associated standard deviation for the cellulose microfibrils in the S2 layer of the cell walls of softwood specimens. The length and orientation of over 1000 cell walls in the irradiated volume of the specimen are measured using quantitative image analysis. From these data are calculated the azimuthal variation of the scattered intensity. The calculated values are compared with the measured values. The undetermined parameters in the analysis are the microfibril angle (M) and the standard deviation (σΦ) of the intensity distribution arising from the wandering of the fibril orientation about the mean value. The two parameters are varied to give the best fit between the calculated and the measured values. Six separate pairs of values are determined for six different values of the angle of incidence of the X-ray beam relative to the normal to the radial direction in the specimen. The results show good agreement. The azimuthal distribution of scattered intensity for the real cell-wall structure is compared with that calculated for an assembly of rectangular cells with the same ratio of transverse to radial cell-wall lengths. Despite the existence of marked differences in the intensity distributions around the zero azimuth angle, the position of the extreme flanks of the distribution is very close for the real and the rectangular cells. This means that useful values of the microfibril angle can be obtained from the curve for the real cells using the Meylan parameter T derived by drawing tangents to the flanks of the intensity distribution and using M = kT. The value of k is M/(M + 2σΦ). Since both of these parameters are determined in the work now described, k is also determined. It is also demonstrated that for β = 45° (where β is the angle between the plane face of the wood specimens and the radial direction) the peaks in the azimuthal intensity distribution for the real and the rectangular cells coincide. If this peak position is Φ45, then the microfibril angle can be determined from the relation M = tan−1(tanΦ45/cos45°), which is precise for rectangular cells.

Application of Small-Angle X-Ray Scattering to Predict Microfibril Angle in Acacia mangium Wood

2010 ◽  
Vol 173 ◽  
pp. 72-77
Author(s):  
Tabet A. Tamer ◽  
Aziz Abdul Haji Fauziah ◽  
Radiman Shahidan
Keyword(s):  
Cell Wall ◽  
Standard Deviation ◽  
Intensity Distribution ◽  
Small Angle ◽  
Cell Walls ◽  
Microfibril Angle ◽  
Acacia Mangium ◽  
Cellulose Microfibrils ◽  
X Ray ◽  
X Ray Scattering

Partially crystalline cellulose microfibrils are wound helically around the longitudinal axis of the wood cell. A method is presented for the measurement, using small-angle X-ray scattering (SAXS), of the microfibril angle, (MFA) and the associated standard deviation for the cellulose microfibrils in the S2 layer of the cell walls of Acacia mangium wood. The length and orientation of the microfibrils of the cell walls in the irradiated volume of the thin samples are measured using SAXS and scanning electron microscope, (SEM). The undetermined parameters in the analysis are the MFA, (M) and the standard deviation (σФ) of the intensity distribution arising from the wandering of the fibril orientation about the mean value. Nine separate pairs of values are determined for nine different values of the angle of the incidence of the X-ray beam relative to the normal to the radial direction in the sample. The results show good agreement. The curve distribution of scattered intensity for the real cell wall structure is compared with that calculated with that assembly of rectangular cells with the same ratio of transverse to radial cell wall length. It is demonstrated that for β = 45°, the peaks in the curve intensity distribution for the real and the rectangular cells coincide. If this peak position is Ф45, Then the MFA can be determined from the relation M = tan-1 (tan Ф45 / cos 45°), which is precise for rectangular cells.

Spiral angle of elementary cellulose fibrils in cell walls ofPicea abies determined by small-angle x-ray scattering

1998 ◽  
Vol 32 (5) ◽  
pp. 335-345 ◽  
Author(s):  
A. Reiterer ◽  
H. F. Jakob ◽  
S. E. Stanzl-Tschegg ◽  
P. Fratzl
Keyword(s):  
Small Angle ◽  
Cell Walls ◽  
X Ray ◽  
X Ray Scattering ◽  
Cellulose Fibrils ◽  
Spiral Angle ◽  
Ray Scattering

Rapid Thermal Oxidation for Passivation of Porous Silicon

1994 ◽  
Vol 342 ◽  
Author(s):  
I. BÁrsony ◽  
J.G.E. Klappe ◽  
É. Vázsonyi ◽  
T. Lohner ◽  
M. Fried
Keyword(s):  
Porous Silicon ◽  
Mechanical Stability ◽  
Porous Substrate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Si Substrates ◽  
Tetragonal Lattice ◽  
Optical Heating ◽  
Vertical Inhomogeneity ◽  
Highly Porous

ABSTRACTChemical and mechanical stability of porous silicon layers (PSL) is the prerequisite of any active (luminescent) or passive (e.g. porous substrate) integrated applications. In this work X-ray diffraction (XRD) was used to analyze quantitatively the strain distribution obtained in different morphology PSL that were prepared on (100) p and p+Si substrates. Tetragonal lattice constant distortion can be as high as 1.4% in highly porous “as-prepared” samples. Incoherent optical heating RTO is governed by the absorption in the oxidized specimen. PSL show vertical inhomogeneity according to interpretation of spectroscopic ellipsometry (SE) data. Oxygen incorporation during RTO is controlled by specific surface (in p+ proportional, in p inversely proportional with porosity), while the developing compressive stress depends on pore size, and decreases with porosity in both morphologies.

scholarly journals Visualising Silicon in Plants: Histochemistry, Silica Sculptures and Elemental Imaging

Cells ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 1066 ◽  
Author(s):  
Gea Guerriero ◽  
Ian Stokes ◽  
Nathalie Valle ◽  
Jean-Francois Hausman ◽  
Christopher Exley
Keyword(s):  
Cell Walls ◽  
Mass Spectrometry Imaging ◽  
Spatial Information ◽  
Cannabis Sativa ◽  
Essential Element ◽  
Molecular Data ◽  
Plant Vigour ◽  
X Ray ◽  
Imaging Approach ◽  
General Improvement

Silicon is a non-essential element for plants and is available in biota as silicic acid. Its presence has been associated with a general improvement of plant vigour and response to exogenous stresses. Plants accumulate silicon in their tissues as amorphous silica and cell walls are preferential sites. While several papers have been published on the mitigatory effects that silicon has on plants under stress, there has been less research on imaging silicon in plant tissues. Imaging offers important complementary results to molecular data, since it provides spatial information. Herein, the focus is on histochemistry coupled to optical microscopy, fluorescence and scanning electron microscopy of microwave acid extracted plant silica, techniques based on particle-induced X-ray emission, X-ray fluorescence spectrometry and mass spectrometry imaging (NanoSIMS). Sample preparation procedures will not be discussed in detail, as several reviews have already treated this subject extensively. We focus instead on the information that each technique provides by offering, for each imaging approach, examples from both silicifiers (giant horsetail and rice) and non-accumulators (Cannabis sativa L.).

Non-cellulosic structural polysaccharides in algal cell walls I. Xylan in siphoneous green algae

1964 ◽  
Vol 160 (980) ◽  
pp. 293-313 ◽  
Keyword(s):  
Relative Humidity ◽  
Cell Walls ◽  
Marine Algae ◽  
Transverse Section ◽  
Algal Cell ◽  
Repeat Distance ◽  
X Ray ◽  
Face View ◽  
Half Turn ◽  
Parallel Arrays

The cell walls of a number of marine algae, namely species of Bryopsis, Caulerpa, Udotea, Halimeda and Penicillus and of one freshwater alga, Dichotomosiphon , are examined using both chemical and physical techniques. It is shown that, with the possible exception of Bryopsis , cellulose is completely absent and that the walls contain instead β -l,3-linked xylan as the structural polysaccharide. Bryopsis contains, in addition, a glucan which is most abundant in the outer layers of the wall and which stains like cellulose. The xylan is microfibrillar but the microfibrils are more strongly adherent than they are in cellulose, and in some species appear in the electron microscope to be joined by short crossed rod-like bodies. The orientation of the microfibrils is found to vary, ranging from a net tendency to transverse orientation through complete randomness to almost perfect longitudinal alinement. The microfibrils are negatively birefringent, so that all walls seen in optical section, and all parallel arrays of microfibrils whether in face view or in section (except strictly transverse section) are negatively birefringent. With Bryopsis , the negative birefringence in face view is overcompensated by the positive birefringence of the incrusting glucan so that the true birefringence of the crystalline polysaccharide is observed only after the glucan is removed. The X-ray diagram of parallel arrays of microfibrils as found, for instance, in Penicillus dumetosus shows that the xylan chains are helically coiled, in harmony with the negative birefringence. It is deduced that the microfibrils consist of hexagonally packed, double-stranded helices. The diameter of the helices increases with increasing relative humidity, as water is taken into the lattice, from 13.7 Å in material dried over phosphorus pentoxide to a maximum of 1.54 Å at 65 % relative humidity when the xylan contains 30 % of its weight as water. The repeat distance along the helix axis ranges from 5.85 Å (dry) to 6.06 Å (wet), the length of a half turn of each helix containing three xylose residues. The incrusting substances in these walls often include a glucan which is said also to be 1,3-linked. The significance of the extensive differences between this xylan and cellulose are examined both as regards some of the physical properties of the respective cell walls and in relation to the taxonomic position of these plants.

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