Lignin Distribution on Cell Wall Micro-Morphological Regions of Fibre in Developmental Phyllostachys pubescens Culms.

Bo Liu,Yuejin Fu,Xianwu Zou,Qian Chen,Botao Li,Qin Zhou,Liming Zhu,Yun Lu,Lina Tang

doi:10.3390/polym14020312

Bo Liu, Yuejin Fu + Show 7 more

Open Access

https://doi.org/10.3390/polym14020312

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Abstract

Bamboo is a natural fibre reinforced composite with excellent performance which is, to a certain extent, an alternative to the shortage of wood resources. The heterogeneous distribution and molecular structure of lignin is one of the factors that determines its performance, and it is the key and most difficult component in the basic research into the chemistry of bamboo and in bamboo processing and utilization. In this study, the distribution of lignin components and lignin content in micro-morphological regions were measured in semi-quantitative level by age and radial location by means of visible-light microspectrophotometry (VLMS) coupled with the Wiesner and Maule reaction. There as guaiacyl lignin and syringyl lignin in the cell wall of the fibre. Lignin content of the secondary cell wall and cell corner increased at about 10 days, reached a maximum at 1 year, and then decreased gradually. From 17 days to 4 years, the lignin content of the secondary cell wall in the outer part of bamboo is higher than that in the middle part (which is, in turn, higher than that in the inner part of the bamboo). VLSM results of the micro-morphological regions showed that bamboo lignification developed by aging. Guaiacyl and syringl lignin units can be found in the cell wall of the fibre, parenchyma, and vessel. There was a difference in lignin content among different ages, different radial location, and different micro-morphological regions of the cell wall. The fibre walls were rich in guaiacyl lignin in the early stage of lignification and rich in syringyl units in the later stage of lignification. The guaiacyl and syringyl lignin deposition of bamboo green was earlier than that of the middle part of bamboo culm, and that of the middle part of bamboo culm was earlier than that of bamboo yellow. The single molecule lignin content of the thin layer is higher than that of thick layers, while the primary wall is higher than the secondary cell wall, showing that lignin deposition is consistent with the rules of cell wall formation. The obtained cytological information is helpful to understand the origin of the anisotropic, physical, mechanical, chemical, and machining properties of bamboo.

Highlights

Bamboo is a profuse, long-lasting resource and the quickest developing and most adaptable plant on Earth
Many excellent properties of bamboo stem are governed by the properties of the cell wall, which can be described in terms of the sub microstructure of cell wall and the localization of cell wall components of cellulose, hemicellulose, and lignin
An important role of lignin in the wood cell wall is to function as a cross-linking matrix between moisture sensitive cellulose and hemicelluloses

Summary

Introduction

Long-lasting resource and the quickest developing and most adaptable plant on Earth. Wood parenchyma cells do not generally contain lignin, but in bamboo culms, lignin widely exists in all kinds of lignified bamboo tissues [10] It is the important component of the fibre cell wall, parenchyma cell wall, and vessel cell wall [11]. Considering the heterogeneous distribution of lignin and the quantitative analysis of the micro morphological region of cell wall from the perspective of bamboo processing and utilization performance is of great significance for the basic research of bamboo chemistry and bamboo processing and utilization. The in situ distribution and the content of lignin component within the fiber located at bamboo green, bamboo timber and bamboo yellow, and located at different cell wall micromorphological regions within fibre cap on radial and longitudinal location were visualized by complementary microscopy techniques (visible-light microspectrophotometry) coupled with the biochemical method (Wiesner and Maule reactions), especially in different cell wall growth stages. The obtained cytological information is helpful to understand the origin of the anisotropic, physical, mechanical, chemical, and machining properties of bamboo

Bamboo Samples

Sectioning and Microscopy

Variation of Lignin Content of SW and CC in Different Radial Location