The dynamic changes in the distribution of lignin and hemicelluloses (xylans and xyloglucans) in cell walls during the differentiation of secondary xylem in Eucommia ulmoides Oliv. were studied by means of ultraviolet light microscopy and transmission electron microscopy combined with immunogold labelling. In the cambial zone and cell expansion zone, xyloglucans were localized both in the tangential and radial walls, but no xylans or lignin were found in these regions. With the formation of secondary wall S1 layer, lignin occurred in the cell corners and middle lamella, while xylans appeared in S1 layer, and xyloglucans were localized in the primary walls and middle lamella. In pace with the formation of secondary wall S2 and S3 layer, lignification extended to S1, S2 and S3 layer in sequence, showing a patchy style of lignin deposition. Concurrently, xylans distributed in the whole secondary walls and xyloglucans, on the other hand, still localized in the primary walls and middle lamella. The results indicated that along with the formation and lignification of the secondary wall, great changes had taken place in the cell walls. Different parts of cell walls, such as cell corners, middle lamella, primary walls and various layers of secondary walls, had different kinds of hemicelluloses, which formed various cell wall architecture combined with lignin and other cell wall components.
杜仲次生木质部分化过程中木质素与半纤维素组分在细胞壁中分布的动态变化
贺新强 崔克明* 李正理
（北京大学生命科学学院，北京100871）
摘要：利用紫外光显微镜、透射电子显微镜结合免疫胶体金标记,研究了杜仲(Eucommia ulmoid es Oliv.)次生木质部分化过程中木质素与半纤维素组分(木葡聚糖和木聚糖)在细胞壁分布的动态变化.在形成层及细胞伸展区域,细胞壁具有木葡聚糖的分布,而没有木聚糖和木质素沉积.随着次生壁S1层的形成,木质素出现在细胞角隅和胞间层,木聚糖开始出现在S1层中,此时木葡聚糖则分布在初生壁和胞间层;随着次生壁S2层及S3层的形成和加厚,木质素逐步由细胞角隅和胞间层扩展到S1、S2和S3层,其沉积呈现出不均匀的块状或片状沉积模式.在次生壁各层形成与其木质化的同时,木聚糖逐渐分布于整个次生壁中,而木葡聚糖仍局限分布于初生壁和胞间层.结果表明,随着细胞次生壁的形成与木质化,细胞壁结构发生较大变化.细胞壁的不同区域,如细胞角隅、胞间层、初生壁和次生壁各层,具有不同的半纤维素组成,其与木质素等细胞壁组分结合共同构成不同的细胞壁分子结构.
关键词： 细胞壁；木质素；半纤维素；次生木质部分化；杜仲
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