Leaf organogenesis is governed by the spatiotemporal activity of the leaf meristem, which has far greater mitotic activity than the shoot apical meristem. The two types of leaf meristems, the plate meristem and the marginal meristem, are distinguished by the location and longevity of their cell proliferative activity. Most leaf lamina outgrowth depends on the plate meristem. The presence of the marginal meristem was a matter of debate in classic anatomy, but recent genetic analyses of leaf growth in Arabidopsis thaliana confirmed its short-lived activity. Several genes key for the regulation of the two meristem types have been identified, and at least superficially, the systems appear to function independently, as they are regulated by different transcription factors and microRNAs. However, many of the details of these regulatory systems, including how the expression of these key factors is spatially regulated, remain unclear. One major unsolved question is the relationship between the plate meristem and the marginal meristem. Here, I present an overview of our current understanding of this topic and discuss questions that remain to be answered.

中文翻译：

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叶分生组织之谜：板分生组织与边缘分生组织的关系

叶器官发生受叶分生组织的时空活动支配，其有丝分裂活动远大于茎顶端分生组织。两种类型的叶分生组织，板分生组织和边缘分生组织，通过其细胞增殖活性的位置和寿命来区分。大多数叶片的生长取决于板分生组织。边缘分生组织的存在在经典解剖学中是一个争论的问题，但最近对拟南芥叶片生长的遗传分析证实了它的短暂活动。已经确定了调节这两种分生组织类型的几个关键基因，至少从表面上看，这些系统似乎独立运作，因为它们受不同的转录因子和 microRNA 的调节。然而，这些监管系统的许多细节，包括如何在空间上调节这些关键因素的表达，仍不清楚。一个未解决的主要问题是板分生组织和边缘分生组织之间的关系。在这里，我概述了我们目前对该主题的理解，并讨论了仍有待回答的问题。