Chemical Imaging of Poplar Wood Cell Walls by Confocal Raman Microscopy

TLDR

Confocal Raman microscopy was used to illustrate changes in molecular composition of secondary cell walls in poplar wood. Two‑dimensional spectral maps were acquired and chemical images generated by integrating characteristic spectral band intensities. The technique directly visualized spatial lignin variation, revealed a 0.5‑μm lignified border in the gelatinous layer, mapped variable cellulose orientation and an S1 layer <0.5 μm, demonstrating that scanning Raman microscopy is a powerful, nondestructive, high‑resolution tool for imaging molecular cell‑wall organization.

Abstract

Abstract Confocal Raman microscopy was used to illustrate changes of molecular composition in secondary plant cell wall tissues of poplar (Populus nigra × Populus deltoids) 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 toward the lumen was observed in the gelatinous layer of poplar 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, nondestructive tool for imaging changes in molecular cell wall organization with high spatial resolution.