Shishkova S, Rost T L, Dubrovsky J G
Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, 62250, Cuernavaca, Morelos, Mexico.
Ann Bot. 2008 Feb;101(3):319-40. doi: 10.1093/aob/mcm251. Epub 2007 Oct 21.
The difference between indeterminate and determinate growth in plants consists of the presence or absence of an active meristem in the fully developed organ. Determinate root growth implies that the root apical meristem (RAM) becomes exhausted. As a consequence, all cells in the root tip differentiate. This type of growth is widely found in roots of many angiosperm taxa and might have evolved as a developmental adaptation to water deficit (in desert Cactaceae), or low mineral content in the soil (proteoid roots in various taxa).
This review considers the mechanisms of determinate root growth to better understand how the RAM is maintained, how it functions, and the cellular and genetic bases of these processes. The role of the quiescent centre in RAM maintenance and exhaustion will be analysed. During root ageing, the RAM becomes smaller and its organization changes; however, it remains unknown whether every root is truly determinate in the sense that its RAM becomes exhausted before senescence. We define two types of determinate growth: constitutive where determinacy is a natural part of root development; and non-constitutive where determinacy is induced usually by an environmental factor. Determinate root growth is proposed to include two phases: the indeterminate growth phase, when the RAM continuously produces new cells; and the termination growth phase, when cell production gradually decreases and eventually ceases. Finally, new concepts regarding stem cells and a stem cell niche are discussed to help comprehend how the meristem is maintained in a broad taxonomic context.
植物中有限生长和无限生长的区别在于完全发育的器官中是否存在活跃的分生组织。有限根生长意味着根尖分生组织（RAM）耗尽。结果，根尖的所有细胞都发生分化。这种生长类型在许多被子植物类群的根中广泛存在，可能是作为对水分亏缺（沙漠仙人掌科）或土壤中低矿物质含量（各种类群中的类菌根根）的一种发育适应而进化而来的。
本综述探讨了有限根生长的机制，以便更好地理解RAM是如何维持的、其功能如何以及这些过程的细胞和遗传基础。将分析静止中心在RAM维持和耗尽中的作用。在根衰老过程中，RAM会变小且其组织结构会发生变化；然而，每个根的RAM在衰老前是否真的会耗尽，这一点尚不清楚。我们定义了两种类型的有限生长：组成型，即有限性是根发育的自然组成部分；非组成型，即有限性通常由环境因素诱导。有限根生长被认为包括两个阶段：无限生长阶段，此时RAM持续产生新细胞；以及终止生长阶段，此时细胞产生逐渐减少并最终停止。最后，讨论了关于干细胞和干细胞微环境的新概念，以帮助在广泛的分类学背景下理解分生组织是如何维持的。
