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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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Related in: MedlinePlus

Intensity of the orientation sensitive 1097 cm−1 band (black circles) and microfibril angles (MFA, triangles) predicted by the PLS1 model from single spectra extracted of every pixel along the line marked in the inset (LW20).
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fig8: Intensity of the orientation sensitive 1097 cm−1 band (black circles) and microfibril angles (MFA, triangles) predicted by the PLS1 model from single spectra extracted of every pixel along the line marked in the inset (LW20).

Mentions: Due to changes in cellulose orientation, the S1 layer can be visualized in the Raman images of wood cross-sections. The estimated MFAs were much higher than in the S2, but were underestimated compared to other methods due to the inclusion of the transition zone and the limit of diffraction limited lateral resolution. Also a clear increase is seen towards the S1, the increase of the integrated intensity of the cellulose band as well as the calculated MFA is gradual (Fig. 8). With a scanning step size (0.25 μm) below the lateral theoretical spatial resolution, the neighbouring area always influences the spectra and, secondly, a natural gradual increase is also proposed within the S1 towards the middle lamella (Donaldson, 2008). So, even if layers can clearly be separated by the Raman imaging approach, adjacent regions can contribute to the Raman spectra if layers smaller than 1 μm are analysed in detail. The mapping approach and pixelwise post-extraction of spectra has the advantage of being able selectively to choose the area for detailed analysis and to exclude borders or gradients which might influence the true values. Within the S2 the predicted MFA values were between 16° and 23° and reached a plateau in the S1 of 50°. Although the MFA values across the cell wall (Fig. 8) are based on more noisy single spectra the predictions are similar to the ones based on the average spectra (Table 3).


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)

Intensity of the orientation sensitive 1097 cm−1 band (black circles) and microfibril angles (MFA, triangles) predicted by the PLS1 model from single spectra extracted of every pixel along the line marked in the inset (LW20).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig8: Intensity of the orientation sensitive 1097 cm−1 band (black circles) and microfibril angles (MFA, triangles) predicted by the PLS1 model from single spectra extracted of every pixel along the line marked in the inset (LW20).
Mentions: Due to changes in cellulose orientation, the S1 layer can be visualized in the Raman images of wood cross-sections. The estimated MFAs were much higher than in the S2, but were underestimated compared to other methods due to the inclusion of the transition zone and the limit of diffraction limited lateral resolution. Also a clear increase is seen towards the S1, the increase of the integrated intensity of the cellulose band as well as the calculated MFA is gradual (Fig. 8). With a scanning step size (0.25 μm) below the lateral theoretical spatial resolution, the neighbouring area always influences the spectra and, secondly, a natural gradual increase is also proposed within the S1 towards the middle lamella (Donaldson, 2008). So, even if layers can clearly be separated by the Raman imaging approach, adjacent regions can contribute to the Raman spectra if layers smaller than 1 μm are analysed in detail. The mapping approach and pixelwise post-extraction of spectra has the advantage of being able selectively to choose the area for detailed analysis and to exclude borders or gradients which might influence the true values. Within the S2 the predicted MFA values were between 16° and 23° and reached a plateau in the S1 of 50°. Although the MFA values across the cell wall (Fig. 8) are based on more noisy single spectra the predictions are similar to the ones based on the average spectra (Table 3).

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