细胞壁的层次: 胞间层、初生壁、炊生壁 Primary cell wall Secondary cell wall
细胞壁的层次： 胞间层、初生壁、次生壁
Primary cell wall Daughter nuclei 5 um A FIGURE 22-30 Light micrograph of young root tip cells of an onion. A thin primary cell wall separates two recently separated cells. I Courtesy of Jim Solliday and Biological Photo Service. I
初生壁的结构模型 4 FIGURE 22-29 Schematic representation of the cell wall of an onion. Cellulose and hemicellulose are arranged into at least three layers in a matrix of pectin polymers. The size of the polymers and their separations are drawn to scale. To simplify the diagram. most of the hemicellulose cross-links are not shown. [Adapted from M. McCann nd k R. Roberts, 1991. in C. Lloyd, ed Primary The Cytoskeletal Basis of Plant Growth and Form, p. 126.1 Pectin Plasma membrane Cellulose 50 nm
初生壁的结构模型
Plasma mbrane Plasmodesma itilayered secondary wall Cytoplasm lamella Structure of the Secondary Cell Wall A FIGURE 22-32 The structure of the secondary cell wall. built up of a series of layers of cellulose. In each layer, the Primary cellulose fibrils run more or less in the same drection, but the wall Plasma direction varies in different layers. As plant cells grow, they membrane deposit new layers of cellulose adjacent to the plasma membrane Thus the oldest layers are in the primary wall ithe outer wall) and in the middle lamella (the pectin- nch part of the cell wall laid down between two daughter cells as they cleave during cell division) Younger regions of the wall--collectively the secondary cell wall -are laid down as successive layers, adjacent to the plasma membrane. The cytoplasms of adjacent cells are usually connected by plasmodesmata that run through the layers of the cell walls Middle lamella Cellulose fibrils of secondary Primary
Structure of the Secondary Cell Wall
C.与细胞壁相关的结构: 牣生紋孔场( Primary pit field)初生壁上有一些较蓐的区蜮。 紋孔(Pit)}次生壁形成时,有一些中断的区城,只有中胶层和初生壁, 这种比较嶙的区蜮称为紋孔。 注意:紋孔也可在没有初生紋孔炀的初生壁上产生。 具缘纹孔,单纹孔,纹孔对,盲纹孔。 pit in secondary pit in secondary wa wall of one cel of adjacent cell secondary wa middle lamella
初生纹孔场（Primary pit field):初生壁上有一些较薄的区域。 纹孔(Pit):次生壁形成时，有一些中断的区域，只有中胶层和初生壁， 这种比较薄的区域称为纹孔。 注意：纹孔也可在没有初生纹孔场的初生壁上产生。 具缘纹孔，单纹孔，纹孔对，盲纹孔。 C. 与细胞壁相关的结构：