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( D) The dissected leaf of the cultivated tomato. The rachis (R) via a structure called a petiolule (Pu). Leaflets are clearly defined as distinct units of the same leaf, which connect with ( C) The dissected leaf of Cardamine hirsuta. Lobes are deep serrations, so the definition of an outgrowth as a serration The asterisk depicts the position of one lobe. ( B) The lobed leaf of the Arabidopsis thaliana relative Arabidopsis lyrata. The asterisk marks one marginal serration. The proximo–distal (P–D) and medio–lateral (M–L) axes are indicated in the image. ( A) A simple, serrated leaf of the Columbia ecotype of Arabidopsis thaliana. Such roles of auxin in different facets of leaf and vascular development is the focus of our article.Īxes of leaf asymmetry and diversity of leaf shape. Over the past 15 years, geneticĪpproaches have led to substantial increase in our understanding of leaf and vascular development, and have provided goodĮvidence that regulated activity of the small indolic growth regulator auxin provides important spatial cues for both processes. Lamina growth and vascular development share common genetic control, and finally (3) how coordination between leaf and vascularĭevelopment is achieved and impacts on generation of final leaf shape and vein arrangement. The questions of (1) what are the specific signaling pathways that sculpt leaf shape and vascular patterns, (2) to what degree
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The pattern of vasculature formation is well aligned with the final geometry of the leaf lamina. Intriguingly, there is also congruence of leaf shape and vein layouts, such that, at least superficially, A common feature of the development of the leaf lamina and vein networks is the repeated use of basic modules.įor example, the iterative emergence of marginal leaf-shape elements, such as serrations, lobes, and leaflets ( Fig. 1A–D), and the arrangement of successive orders of branched veins result in different types of leaf geometries and vascular Leaf form and vascular patterns provide some of the most impressive examples of the complexity of biological shapes generated These feedbacks may facilitate the iterative generation of basic modules that underlies morphogenesis of both leaves and vasculature. A key feature of auxin action is the existence of feedback loops through which auxin regulates its own transport. The growth regulator auxin has a key role in both initiation and elaboration of final morphology of both leaves and vascular Understanding the processes that endow leaves and vein networks with ordered and closelyĪligned shapes has captured the attention of biologists and mathematicians since antiquity. Leaf vascular tissues, whichĪct as conduits of both nutrients and signaling information, are organized in networks of different architectures that usually Leaves are the main photosynthetic organs of vascular plants and show considerable diversity in their geometries, rangingįrom simple spoonlike forms to complex shapes with individual leaflets, as in compound leaves.