• Veber, A.; Zancajo, V.M.R.; Puskar, L.; Schade, U.; Kneipp, J.: In situ infrared imaging of the local orientation of cellulose fibrils in plant secondary cell walls. Analyst 148 (2023), p. 4138-4147

Open Access Version

The mechanical and chemical properties of plant cell walls greatly rely on the supramolecular assembly ofcellulosefibrils. To study the local orientation of cellulose in secondary plant cell walls, diffraction limitedinfrared (IR) micro-spectroscopic mapping experiments were conducted at different orientation of trans-verse leaf section of the grassSorghum bicolorwith respect to the polarization direction of the IR radi-ation. Two-dimensional maps, based on polarization-sensitive absorption bands of cellulose wereobtained for different polarization angles. They reveal a significant degree of anisotropy of the cellulosemacromolecules as well as of other biopolymers in sclerenchyma and xylem regions of the cross section.Quantification of the signals assigned to polarization sensitive vibrational modes allowed to determine thepreferential orientation of the sub-micron cellulosefibrils in single cell walls. A sample of crystallinenano-cellulose comprising both a single microcrystal as well as unordered layers of nanocrystals wasused for validation of the approach. The results demonstrate that diffraction limited IR micro-spec-troscopy can be used to study hierarchically structured materials with complex anisotropic behavior.