Heteroblasty in the moss, Aphanoregma patens (Physcomitrella patens), results from progressive modulation of a single fundamental leaf developmental programme
Heteroblasty in the moss, Aphanoregma patens (Physcomitrella patens), results from progressive modulation of a single fundamental leaf developmental programme
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DOI：
10.1179/1743282013y.0000000058
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发表时间：
2013-01-01
影响因子：
1.9
通讯作者：
Ashton, Neil W.
中科院分区：
文献类型：
--
作者：
Barker, Elizabeth I.;Ashton, Neil W.
成熟的Aphanoregma patens(Hedw.)林德布。(Physcomitrella patens(Hedw.)布鲁赫·希姆普。在B.S.G.)配子体的大小和形状与其底部的配子体明显不同。为了确定这些差异是如何在发育过程中产生的，我们首先检查了茎上连续叶片和不同发育阶段叶片之间的质量和数量差异。连续叶之间的差异很小，而且是累积的。细胞数量和大小的局部变化结合在一起形成了形状规则的、大致两侧对称的叶片，这表明细胞分裂和细胞扩展在器官水平上是区域性调节和协调的。中脉和边缘齿是离散的特征，缺乏这些特征的叶片的细胞形状的变化预示着这些特征的出现。在叶原基中，细胞增殖是早期叶片形状和大小变化的主要原因，随着细胞扩张成为叶片生长和形态发生的主要贡献者，细胞增殖可能会继续下去。因此，Physcomitrella中的叶异形可能是由于外力和/或内力对单个发育程序的调节，随着配子体的生长，外力和/或内力的强度逐渐改变。我们将外源细胞分裂素和生长素分别应用于生长培养，以探讨它们对叶片生长的影响。细胞分裂素和生长素分别促进叶片细胞分裂和叶片细胞伸长。此外，暴露于外源生长素的配子梗的年轻上部叶与未处理植物的基生叶非常相似。因此，内源细胞分裂素和生长素可能是调控叶片形态发生和异型叶形成的内力之一。
Leaves at the apex of a mature Aphanoregma patens (Hedw.) Lindb. (Physcomitrella patens (Hedw.) Bruch Schimp. in B.S.G.) gametophore differ markedly in size and form from those at its base. To determine how these differences are produced during development, we first examined qualitative and quantitative differences between successive leaves along the stem and among leaves at different developmental stages. Differences between successive leaves were slight and cumulative. Local changes in cell number and size combined to produce a regularly shaped and approximately bilaterally symmetrical leaf suggesting that cell division and cell expansion are regionally regulated and coordinated at the organ level. The midrib and marginal teeth are discrete characters, which were prefigured by changes in cell shape in leaves that lacked these characters. In leaf primordia, cell proliferation was responsible for most of the changes in leaf form and size early in development and may have continued as cell expansion took over as the primary contributor to leaf growth and morphogenesis. Thus, leaf heteroblasty in Physcomitrella probably results from modulation of a single developmental programme by external and/or internal forces, which alter progressively in intensity as a gametophore grows. We applied exogenous cytokinin and auxin separately to growing cultures to explore their effects on leaf growth. Cytokinin and auxin stimulated leaf cell division and leaf cell elongation, respectively. Also, young upper leaves of gametophores exposed to exogenous auxin closely resembled basal leaves of untreated plants. Therefore, endogenous cytokinins and auxins may be among the modulating internal forces involved in leaf morphogenesis and the establishment of leaf heteroblasty.