Running head: Raman imaging of secondary plant cell walls

Confocal Raman microscopy was used to illustrate changes of molecular composition in secondary plant cell wall tissues of poplar wood. Two–dimensional spectral maps were acquired and chemical images calculated by integrating the intensity of characteristic spectral bands. This enabled direct visualization of the spatial variation of the lignin content without any chemical treatment or staining of the cell wall. A small (0.5 μm) lignified border towards the lumen was observed in the gelatinous (G-) layer of poplar (Populus nigra x P. deltoids) tension wood. The variable orientation of the cellulose was also characterized, leading to visualization of the S1 layer with dimensions smaller than 0.5 μm. Scanning Raman microscopy was thus shown to be a powerful, non-destructive tool for imaging changes in molecular cell wall organization with high spatial resolution. www.plantphysiol.org on October 23, 2017 Published by Downloaded from Copyright © 2006 American Society of Plant Biologists. All rights reserved.