Section of Plant Biology, Division of Biological Sciences, University of California, Davis, California 95616 USA;
Am J Bot. 2002 Jun;89(6):908-20. doi: 10.3732/ajb.89.6.908.
Developmental and physiological studies of roots are frequently limited to a post-germination stage. In Arabidopsis, a developmental change in the root meristem architecture during plant ontogenesis has not previously been studied and is addressed presently. Arabidopsis thaliana have closed root apical organization, in which all cell file lineages connect directly to one of three distinct initial tiers. The root meristem organization is dynamic and changes as the root ages from 1 to 4 wk post-germination. During the ontogeny of the root, the number of cells within the root apical meristem (RAM) increases and then decreases due to changes in the number of cortical layers and number of cell files within a central cylinder. The architecture of the initial tiers also changes as the root meristem ages. Included in the RAM's ontogeny is a pattern associated with the periclinal divisions that give rise to the middle cortex and endodermis; the three-dimensional arrangement of periclinally dividing derivative cells resembles one gyre of a helix. Four- or 5-wk-old roots exhibit a disorganized array of vacuolated initial cells that are a manifestation of the determinate nature of the meristem. Vascular cambium is formed via coordinated divisions of vascular parenchyma and pericycle cells. The phellogen is the last meristem to complete its development, and it is derived from pericycle cells that delineate the outer boundary of the root.
根系的发育和生理学研究通常仅限于萌发后阶段。在拟南芥中，植物个体发育过程中根分生组织结构的发育变化以前没有被研究过，目前正在研究这个问题。拟南芥具有封闭的根顶端组织，其中所有细胞谱系直接连接到三个不同初始层中的一个。根分生组织组织是动态的，随着根从萌发后 1 到 4 周的年龄而变化。在根的个体发育过程中，由于皮层层数和中央柱内细胞谱系数量的变化，根尖分生组织（RAM）内的细胞数量增加，然后减少。初始层的结构也随着根分生组织的年龄而变化。RAM 的个体发育包括与中皮层和内皮层起源的垂周分裂相关的模式；垂周分裂衍生细胞的三维排列类似于螺旋的一个涡旋。4 或 5 周龄的根表现出排列不规则的泡状初始细胞，这是分生组织确定性的表现。维管形成层通过维管薄壁组织和中柱细胞的协调分裂形成。木栓形成层是最后完成发育的分生组织，它来源于界定根外部边界的中柱细胞。
