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Title
Anatomy cell wall ultrastructure and inhomogeneity in lignin distribution of Broussonetia papyrifera
Authors
Z. H. ZHANG Z. JI J. F. MA and F. XU
Received
November 21, 2011
Published
Volume 46, Issue 3-4 March-April
Keywords
Broussonetia papyrifera (Linn.) Vent, anatomy, ultrastructure, lignin distribution, fluorescence microscopy
Abstract
Broussonetia papyrifera (Linn.) Vent has been attracting interest recently as a valuable wood source for pulping and papermaking manufacturing. The present study aims to determine the anatomical structure, ultrastructure and distribution of lignin in the fiber cell walls of this shrub, using electron microscopy, fluorescence microscopy (FM) and confocal Raman microscopy, which, to our knowledge, has not been reported before. Anatomical observation by electron microscopy indicates that Broussonetia papyrifera (Linn.) Vent is a diffuse-porous wood, consisting of fibers, vessel members and ray parenchyma. As shown by TEM images, the fiber cell wall is typically divided into three layers: middle lamellar (ML), primary wall (P) and secondary wall (S1, S2 and S3). TEM and fluorescence analyses showed that lignin concentrations in compound middle lamella (CML) and cell corner (CC) were higher than in the secondary wall. More detailed information on lignin composition and distribution in different cell wall layers was obtained in situ by confocal Raman microscopy. Raman images of lignin distribution were generated by integrating over the intensity of the 1605 cm?1 band (1712-1519 cm-1). Raman images and spectra of lignin in various morphological regions revealed that the lignin content followed a decreasing order: CC > CML > S2.
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