TOPOCHEMICAL DISTRIBUTION OF LIGNIN AND CELLULOSE IN POPULUS NIGRA DETERMINED BY MICRO-RAMAN SPECTROSCOPY

摘要

Topochemical distribution of lignin and cellulose in individual cell wall layers of Populus nigra stem was determined by transmission electron microscopy (TEM) and confocal Raman microscopy. TEM images exhibited that the fiber wall is typically differentiated into three layers: middle lamella (ML), primary wall (P) and secondary wall (S1, S2 and S3), and the staining intensities represent differing lignin concentrations. In situ Raman images calculated by integrating over the intensity of characteristic spectral bands enabled visualization of the spatial variation in lignin and cellulose. Raman images acquired by integrating over spectral band at 1605 cm-1 suggested that higher lignin concentration was visualized in the cell corner (CC), the compound middle lamella (CML) and the secondary wall of ray parenchyma. Cellulose distribution followed by taking the band regions around 2897 cm-1 into account showed the opposite pattern with the highest concentration in fiber secondary wall.