Bryophytes and vascular plants represent the broadest evolutionary divergence in the land plant lineage, and comparative analyses of development spanning this divergence therefore offer opportunities to identify truisms of plant development in general. In vascular plants, organs are formed repetitively around meristems at the growing tips in response to positional cues. In contrast, leaf formation in mosses and leafy liverworts occurs from clonal groups of cells derived from a daughter cell of the apical stem cell known as merophytes, and cell lineage is a crucial factor in repetitive organ formation. However, it remains unclear whether merophyte lineages are a general feature of repetitive organ formation in bryophytes as patterns of organogenesis in thalloid liverworts are unclear. To address this question, we developed a clonal analysis method for use in the thalloid liverwort Marchantia polymorpha, involving random low-frequency induction of a constitutively expressed nuclear-targeted fluorescent protein by dual heat-shock and dexamethasone treatment. M. polymorpha thalli ultimately derive from stem cells in the apical notch, and the lobes predominantly develop from merophytes cleft to the left and right of the apical cell(s). Sector induction in gemmae and subsequent culture occasionally generated fluorescent sectors that bisected thalli along the midrib and were maintained through several bifurcation events, likely reflecting the border between lateral merophytes. Such thallus-bisecting sectors traversed dorsal air chambers and gemma cups, suggesting that these organs arise independently of merophyte cell lineages in response to local positional cues.

中文翻译：

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位置提示可调节多形草地形马钱子中的背器官形成。

苔藓植物和维管植物代表着陆地植物谱系中最广泛的进化差异，因此跨越这一差异的发展比较分析因此提供了总体上确定植物发展合理性的机会。在维管植物中，响应位置提示，在分生组织周围的生长尖端重复形成器官。相反，苔藓和叶状艾蒿中的叶子形成是来自克隆的细胞群的克隆群，这些细胞是由顶生干细胞的子代细胞（称为旱生植物）衍生的，细胞谱系是重复器官形成的关键因素。但是，尚不清楚苔藓植物中是否有赘生植物谱系是重复器官形成的普遍特征，因为尚不清楚藻类艾蒿的器官发生模式。为了解决这个问题，我们开发了一种用于拟南芥地衣多形花March的克隆分析方法，涉及通过热休克和地塞米松双重处理，随机低频诱导组成型表达的核靶向荧光蛋白。多形藻（M. polymorpha thalli）最终起源于根尖凹口中的干细胞，并且叶主要从裂殖层分裂到根尖细胞的左侧和右侧。胚芽中的扇形诱导和随后的培养有时会产生荧光扇形，该扇形沿着中脉将拟南芥一分为二，并通过多次分叉事件得以维持，这很可能反映了侧生赘生物之间的边界。这类将球体一分为二的区域横穿了背侧气室和宝石杯，