Department of Developmental Biology, Research School of Biological Sciences, Australian National University, P.O. Box 475, 2601, Canberra, A.C.T., Australia.
Planta. 1978 Jan;143(2):161-79. doi: 10.1007/BF00387788.
Complexes of microtubules, vesicles, and (to varying degrees) dense matrix material around the microtubules were seen along the edges of cells in root apices of Azolla pinnata R.Br. (viewing the cells as polyhedra with faces, vertices and edges). They are best developed after cytokinesis has been completed, when the daughter cells are reinstating their interphase arrays of microtubules. They are not confined to edges made by the junction of new cell plates with parental walls, but occur also along older edges. Similar matrices and vesicles are seen amongst phragmoplast microtubules and where pre-prophase bands intersect the edges of cells. It is suggested that the complexes participate in the development of cortical arrays of microtubules. The observations are combined with others, made on pre-prophase bands and on the substructure of cortical arrays lying against the faces of cells, to develop an hypothesis on the development of cortical microtubules, summarised below: Microtubules are nucleated along the edges of cells, at first growing in unspecified orientations and then becoming bridged to the plasma membrane. Parallelism of microtubules in the arrays arises by inter-tubule cross-bridging. Lengths of microtubule are released from, or break off, the nucleating centres and are moved out onto the face of the cell by intertubule and tubule-membrane sliding, thus accounting for the presence there of short tubules with randomly placed terminations. The nucleating zones along cell edges might have vectorial properties, and thus be able to control the orientation of the microtubules on the different faces of the cell. Also, localised activation could generate localised arrays, especially pre-prophase bands in specified sites and planes. Two possible reasons for the spatial restriction of nucleation to cell edges are considered. One is that the geometry of an edge is itself important; the other is that along most cell edges there is a persistent specialised zone, inherited at cytokinesis by the daughter cells when the cell plate bisects the former pre-prophase-band zone.
在满江红根尖细胞的边缘，沿着微管的边缘，可以看到微管、囊泡以及（在不同程度上）致密基质物质的复合物（将细胞视为具有面、顶点和边缘的多面体）。在细胞分裂完成后，当子细胞重新建立它们的微管间期排列时，这些复合物发育得最好。它们不仅局限于新细胞板与母壁交界处形成的边缘，而且也出现在较老的边缘上。在成膜体微管之间和前期带与细胞边缘相交的地方，也可以看到类似的基质和囊泡。有人认为这些复合物参与了皮层微管的发育。这些观察结果与在前期带和位于细胞面的皮层微管束亚结构上的其他观察结果相结合，提出了一个关于皮层微管发育的假说，总结如下：微管首先在细胞边缘沿着特定的边缘生长，在最初的时候，它们的生长方向不确定，然后与质膜桥接。在阵列中的微管的平行度是通过微管之间的交叉桥接产生的。微管束的长度从核中心释放或断裂，并通过微管束和管-膜滑动移动到细胞的面上，从而解释了在那里存在具有随机放置的末端的短管。细胞边缘的核形成区可能具有向量特性，因此能够控制微管在细胞不同面上的方向。此外，局部激活可以产生局部的排列，特别是在特定的位置和平面上产生前期带。考虑到核形成局限于细胞边缘的空间限制的两个可能原因。一个是边缘的几何形状本身很重要；另一个是，在大多数细胞边缘，存在一个持久的专门区域，在细胞分裂时，子细胞继承了前前期带区域，当细胞板将其分为两部分时。
