Distribuição espacial da lignina na parede celular da madeira de Eucalyptus grandis

Abstract

Lignin is an important component of the cell wall that contributes to the waterproofing of xylem conducting elements, which contribute to the cell stiffness, physical conformation of the plant, resistance to compression in the wood, and it is also of great importance for the energy industry. It is known that there are differences in the lignin content between normal and reaction wood; however, its distribution in the cell wall is little known. In this context, the aim of this work was to analyze the spatial distribution of lignin content in the cell wall of normal and of reaction wood fibers of Eucalyptus grandis. Two 28-year-old trees were used in this study, one tree with erect trunk and another with inclined trunk. 5 cm thick discs were removed at 1.30 m from the soil (DBH) and at 25% of the trees total height; from which the normal wood was analyzed, the reaction wood and the wood opposed to it. Samples of the wood were collected from the pith to bark in three positions: internal, intermediate and external, from which histological sections were prepared and used for analysis in the confocal laser microscope. The tensile wood showed a 40% lower fluorescence signal intensity than the normal wood. A pattern of variation of lignin fluorescence intensity in the pith to bark direction was not observed. There was no statistical difference in the lignin intensity between the two heights sampled. In the woods analyzed, the middle lamella and cell corner regions showed higher lignin fluorescence intensity