Pinnately ramified ensiform leaves in the genus Marathrum, (Podostemaceae-Podostemoideae) |
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Authors: | I Jäger-Zürn A Novelo R C T Philbrick M Piepenbring |
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Institution: | 1. Hainerbergweg 61, 61462, K?nigstein, Germany 2. Departamento de Botánica, Instituto de Biología, Universidad Nacional Autónoma de Néxico, D.F. 04510, México, México 3. Department of Biological and Environmental Sciences, Western Connecticut State University, Danbury, CT, 06810, USA 4. Institute for Ecology, Evolution and Biodiversity, University of Frankfurt, Siesmayerstr. 70-72, 60323, Frankfurt, Germany
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Abstract: | The paper deals with the complex leaves of three species of the aquatic genus Marathrum (M. minutiflorum, M. rubrum and M. schiedeanum). It is shown that they represent pinnately ramified ensiform leaves. The dissection of the leaves contributes to surface
enlargement and thus to improvement of their hydrophylls function. The ensiform structure is confirmed by the transverse position
of the sheathing lower leaf zone and the subsequent intercalary elongational growth proceeding in the median plane towards
the abaxial side of the leaf (upper leaf zone). The petiole continues into the rachis-like central axis of the blade from
which pinnate-like segments diverge at the adaxial and abaxial edge of the ensiform blade. The segments give rise to tufts
of clavate enations that end in long filaments. The filigree pinnately segmented ensiform leaves of Marathrum are interpreted as a further development of the fan-shaped and irregularly lobate ensiform leaves occurring in Mourera and Apinagia. Pinnately ramified ensiform leaves obviously evolved in convergence to the common type of pinnate leaves found in angiosperms. |
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Keywords: | Podostemaceae Podostemoideae Marathrum convergence enation ensiform leaf pinnate leaf |
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