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Developmental and Structural Section

Tomescu, Alexandru Mihail Florian [1], Rothwell, Gar W. [2].

Reiteration - the fern perspective.

Reiteration is defined as the reappearance of the juvenile form on a mature structure, or the repetition of the same architectural unit within an organism. This constructional feature evolved in several plant lineages and is extensively documented in seed plants, where reiteration arises from axillary meristems and the reiterative units are almost always stems. By contrast to this rigid reiterative pathway that produces shoots on other shoots, ferns are characterized by a wider range of reiterative architectures. In some ferns (e.g., Lomagramma) rhizomes are reiterated on rhizomes from proleptic buds, mirroring the cauline-cauline reiteration of seed plants. In other ferns reiterative units are produced on leaves. Leaf buds (latent crosiers) borne on frond rachides in members of the Gleicheniaceae, Schizaeaceae, Dennstaedtiaceae, and Matoniaceae develop into reiterative fronds (foliar-foliar reiteration). On the other hand, the leaves of many ferns (Dennstaedtiaceae, Pteridaceae, Hymenophyllaceae, Aspleniaceae) have the capacity to initiate shoots from their surfaces (foliar-cauline reiteration). Such reiterative rhizomes (epiphyllous shoots) bear roots and leaves and develop into whole plants. Whereas epiphyllous shoots are known in several Carboniferous fossil ferns (Botryopteris, Tubicaulis, Anachoropteris, Psalixochlaena), only one fossil fern is known with latent crosiers, the Late Pennsylvanian Anachoropteris clavata. Recent reconstruction of this filicalean as a whole plant provides a unique example for the co-occurrence of two reiterative pathways in the same species: reiterative fronds and reiterative rhizomes; both types of reiterative units are produced on frond rachides. This combination documents the sophisticated structure and developmental pathways achieved by filicalean ferns during their first major evolutionary radiation.

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1 - Humboldt State University, Department of Biological Sciences, Arcata, California, 95521, USA
2 - Ohio University, Department of Environmental & Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA


Presentation Type: Oral Paper
Session: 24-4
Location: Salon A - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 8:45 AM
Abstract ID:151

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