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Cellulose microfibril orientation of Picea abies and its variability at the micron-level determined by Raman imaging.

Gierlinger N, Luss S, König C, Konnerth J, Eder M, Fratzl P - J. Exp. Bot. (2009)

Bottom Line: The functional characteristics of plant cell walls depend on the composition of the cell wall polymers, as well as on their highly ordered architecture at scales from a few nanometres to several microns.Raman spectra of wood acquired with linear polarized laser light include information about polymer composition as well as the alignment of cellulose microfibrils with respect to the fibre axis (microfibril angle).With the prerequisite of geometric sample and laser alignment, exact MFA prediction can complete the picture of the chemical cell wall design gained by the Raman imaging approach at the micron level in all plant tissues.

View Article: PubMed Central - PubMed

Affiliation: Johannes Kepler University Linz, Institute of Polymer Science, Altenberger Strasse 69, Linz, Austria.

ABSTRACT
The functional characteristics of plant cell walls depend on the composition of the cell wall polymers, as well as on their highly ordered architecture at scales from a few nanometres to several microns. Raman spectra of wood acquired with linear polarized laser light include information about polymer composition as well as the alignment of cellulose microfibrils with respect to the fibre axis (microfibril angle). By changing the laser polarization direction in 3 degrees steps, the dependency between cellulose and laser orientation direction was investigated. Orientation-dependent changes of band height ratios and spectra were described by quadratic linear regression and partial least square regressions, respectively. Using the models and regressions with high coefficients of determination (R(2) > 0.99) microfibril orientation was predicted in the S1 and S2 layers distinguished by the Raman imaging approach in cross-sections of spruce normal, opposite, and compression wood. The determined microfibril angle (MFA) in the different S2 layers ranged from 0 degrees to 49.9 degrees and was in coincidence with X-ray diffraction determination. With the prerequisite of geometric sample and laser alignment, exact MFA prediction can complete the picture of the chemical cell wall design gained by the Raman imaging approach at the micron level in all plant tissues.

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(A–D) Raman mappings of spruce latewood with the incident laser polarization direction (green lines) parallel to the x-axis (A, C) and parallel to the y-axis (B, D). Integration over the lignin bands (1542–1696 cm−1) results in identical Raman images (A, B), whereas integration over the orientation-sensitive cellulose band at 1095 cm−1 enhances the S1 layers with a high microfibril angle in the polarization direction (C, D). Spectra for microfibril angle prediction were extracted from the separated layers parallel to the laser polarization direction (tangential walls C, radial walls D).
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fig5: (A–D) Raman mappings of spruce latewood with the incident laser polarization direction (green lines) parallel to the x-axis (A, C) and parallel to the y-axis (B, D). Integration over the lignin bands (1542–1696 cm−1) results in identical Raman images (A, B), whereas integration over the orientation-sensitive cellulose band at 1095 cm−1 enhances the S1 layers with a high microfibril angle in the polarization direction (C, D). Spectra for microfibril angle prediction were extracted from the separated layers parallel to the laser polarization direction (tangential walls C, radial walls D).

Mentions: On the cross-sectional areas the cell wall layers can be visualized by integrating over different wavenumber ranges (Fig. 5A–D). By integrating over the lignin band, the highly lignified cell corners (CC) and compound middle lamella (CML) are distinguished from the secondary cell wall (S2) in spruce latewood (Fig. 5A). The direction of the incident laser polarization direction has no influence on the lignin integration and the same results are observed on turning the laser polarization from 0° (parallel to the x-axis) to 90° (perpendicular) (Fig. 5A, B). Restricting the integration on the 1097 cm−1 cellulose band highlights a small layer in the laser polarization direction (Fig. 5C, D). Consequently, if the laser is parallel to the x-direction the tangential walls are emphasized (Fig. 5C), while if the laser is perpendicular to the x-direction the radial walls show high intensity (Fig. 5D). This small layer represents the S1 layer and shows high intensity, because the microfibril angle (MFA) is large and thus the cellulose fibrils and the C-C, C-O stretching are not strictly perpendicular like in the S2, but with an angle (Fig. 1B).


Cellulose microfibril orientation of Picea abies and its variability at the micron-level determined by Raman imaging.

Gierlinger N, Luss S, König C, Konnerth J, Eder M, Fratzl P - J. Exp. Bot. (2009)

(A–D) Raman mappings of spruce latewood with the incident laser polarization direction (green lines) parallel to the x-axis (A, C) and parallel to the y-axis (B, D). Integration over the lignin bands (1542–1696 cm−1) results in identical Raman images (A, B), whereas integration over the orientation-sensitive cellulose band at 1095 cm−1 enhances the S1 layers with a high microfibril angle in the polarization direction (C, D). Spectra for microfibril angle prediction were extracted from the separated layers parallel to the laser polarization direction (tangential walls C, radial walls D).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2803219&req=5

fig5: (A–D) Raman mappings of spruce latewood with the incident laser polarization direction (green lines) parallel to the x-axis (A, C) and parallel to the y-axis (B, D). Integration over the lignin bands (1542–1696 cm−1) results in identical Raman images (A, B), whereas integration over the orientation-sensitive cellulose band at 1095 cm−1 enhances the S1 layers with a high microfibril angle in the polarization direction (C, D). Spectra for microfibril angle prediction were extracted from the separated layers parallel to the laser polarization direction (tangential walls C, radial walls D).
Mentions: On the cross-sectional areas the cell wall layers can be visualized by integrating over different wavenumber ranges (Fig. 5A–D). By integrating over the lignin band, the highly lignified cell corners (CC) and compound middle lamella (CML) are distinguished from the secondary cell wall (S2) in spruce latewood (Fig. 5A). The direction of the incident laser polarization direction has no influence on the lignin integration and the same results are observed on turning the laser polarization from 0° (parallel to the x-axis) to 90° (perpendicular) (Fig. 5A, B). Restricting the integration on the 1097 cm−1 cellulose band highlights a small layer in the laser polarization direction (Fig. 5C, D). Consequently, if the laser is parallel to the x-direction the tangential walls are emphasized (Fig. 5C), while if the laser is perpendicular to the x-direction the radial walls show high intensity (Fig. 5D). This small layer represents the S1 layer and shows high intensity, because the microfibril angle (MFA) is large and thus the cellulose fibrils and the C-C, C-O stretching are not strictly perpendicular like in the S2, but with an angle (Fig. 1B).

Bottom Line: The functional characteristics of plant cell walls depend on the composition of the cell wall polymers, as well as on their highly ordered architecture at scales from a few nanometres to several microns.Raman spectra of wood acquired with linear polarized laser light include information about polymer composition as well as the alignment of cellulose microfibrils with respect to the fibre axis (microfibril angle).With the prerequisite of geometric sample and laser alignment, exact MFA prediction can complete the picture of the chemical cell wall design gained by the Raman imaging approach at the micron level in all plant tissues.

View Article: PubMed Central - PubMed

Affiliation: Johannes Kepler University Linz, Institute of Polymer Science, Altenberger Strasse 69, Linz, Austria.

ABSTRACT
The functional characteristics of plant cell walls depend on the composition of the cell wall polymers, as well as on their highly ordered architecture at scales from a few nanometres to several microns. Raman spectra of wood acquired with linear polarized laser light include information about polymer composition as well as the alignment of cellulose microfibrils with respect to the fibre axis (microfibril angle). By changing the laser polarization direction in 3 degrees steps, the dependency between cellulose and laser orientation direction was investigated. Orientation-dependent changes of band height ratios and spectra were described by quadratic linear regression and partial least square regressions, respectively. Using the models and regressions with high coefficients of determination (R(2) > 0.99) microfibril orientation was predicted in the S1 and S2 layers distinguished by the Raman imaging approach in cross-sections of spruce normal, opposite, and compression wood. The determined microfibril angle (MFA) in the different S2 layers ranged from 0 degrees to 49.9 degrees and was in coincidence with X-ray diffraction determination. With the prerequisite of geometric sample and laser alignment, exact MFA prediction can complete the picture of the chemical cell wall design gained by the Raman imaging approach at the micron level in all plant tissues.

Show MeSH
Related in: MedlinePlus