TAILIEUCHUNG - Báo cáo khoa học: "Molecular structure and biochemical properties of lignins in relation to possible self-organization of lignin networks"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài:"Molecular structure and biochemical properties of lignins in relation to possible self-organization of lignin networks. | 848s Ann. Sci. For. 1989 46 suppl. 848s-855s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Molecular structure and biochemical properties of lignins in relation to possible self-organization of lignin networks B. Monties Laboratoire de Chimie Biologique INRA CBAI Institut National Agronomique Paris-Grignon Centre de Grignon 78850 Thiverval-Grignon France Introduction This review briefly recalls chemical data related to the variations in the molecular structure of lignin and mainly discusses the biochemical heterogeneity and occurrence of associations between lignins and other cell wall components. In an attempt to relate the formation of such lignin networks to possible functions of lignins a new hypothesis on the self-organization properties of lignin is presented. From a biochemical point of view lignins are particularly complex polymers whose chemical structure changes within plant species organs tissues cells and even cell fractions. Furthermore from a physiological point of view lignin biosynthesis is unusual in that the final polymerization step is only enzymatically initiated and is random chemically directed. Occurrence of such random synthesis raises the central question of the origin of the biological fitness of lignification to the life cycle of plants. This question is relevant not only for the formation of abnormal lignins and lignin-like compounds in reaction woods and wounded and diseased tissues but also in the case of normal lignin in wood xylem. Such random polymerization may also be relevant in relation to the evolution of the quality of the lignocellulosic products such as during heartwood forma tion drying of logs and sawings and hardboard and paper manufacture as suggested respectively for example by Sar-kanen 1971 Northcote 1972 Fry 1986 Back 1987 Jouin et al. 1988 and Horn and Setterholm 1988 . This review focuses thus on self-organization and recalls only briefly the chemical and biochemical properties of lignin in relation to

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