Mucilage is extruded from the bark of Pseudolarix amabilis and Abies nephrolepis upon injury. The aim of this study was to characterize the structure and chemical contents of mucilage extruded from mucilage cells (MCs) in the bark of these species. A large number of MCs containing translucent or dark materials in their lumina were observed in the secondary phloem of P. amabilis and A. nephrolepis. The translucent or dark materials in MCs stained positive with ruthenium red and PAS, indicating the presence of polysaccharides. The average length and diameter of MC in P. amabilis were 1500 μm and 254 μm, respectively, and the corresponding values for A. nephrolepis were 419 μm and 166 μm. Chemical analysis of low molecular weight fractions prepared from mucilage by HPAEC-PAD showed sucrose, glucose and fructose peaks, and in addition galacturonic acid and fucose peaks. Furthermore, 1H NMR spectra for the high molecular weight fraction showed the signals characteristic of pectin. This demonstrates that the mucilage consists mainly of low molecular weight carbohydrates and high molecular weight polysaccharide pectin.
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