Comparative morphology of reproductive structures in heterosporous water ferns and a reevaluation of the sporocarp
Abstract
Heterosporous water ferns (Marsileaceae and Salviniaceae) are the only extant group
of plants to have evolved heterospory since the Paleozoic. These ferns possess unusual
reproductive structures traditionally termed "sporocarps." Using an evolutionary framework,
we critically examine the complex homology issues pertaining to these structures.
Comparative morphological study reveals that all heterosporous ferns bear indusiate
sori on a branched, nonlaminate structure that we refer to as the sorophore; this
expanded definition highlights homology previously obscured by the use of different
terms. By using a homology-based concept, we aim to discontinue the use of historically
and functionally based morphological terminology. We recognize the sorophore envelope
as a structure that surrounds the sorophore and sori. The sorophore envelope is present
in Marsileaceae as a sclerenchymatous sporocarp wall and in Azolla as a parenchymatous
layer, but it is absent in Salvinia. Both homology assessments and phylogenetic character-state
reconstructions using the Cretaceous fossil Hydropteris are consistent with a single
origin of the sorophore envelope in heterosporous ferns. Consequently, we restrict
the term "sporocarp" to a sorophore envelope and all it contains. Traditional usage
of "sporocarp" is misleading because it implies homology for nonhomologous structures,
and structures historically called sporocarps in Salviniaceae are more appropriately
referred to as sori. © 2006 by The University of Chicago. All rights reserved.
Type
Journal articleSubject
Science & TechnologyLife Sciences & Biomedicine
Plant Sciences
morphology
ferns
homology
Marsileaceae
Salviniaceae
sporocarp
SALVINIA LEAVES
MARSILEA VESTITA
AZOLLA-PINNATA
PHYLOGENY
SEQUENCES
DIFFERENTIATION
MORPHOGENESIS
EVOLUTION
SPORES
LEAF
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https://hdl.handle.net/10161/21856Published Version (Please cite this version)
10.1086/503848Publication Info
Nagalingum, NS; Schneider, H; & Pryer, KM (2006). Comparative morphology of reproductive structures in heterosporous water ferns and
a reevaluation of the sporocarp. International Journal of Plant Sciences, 167(4). pp. 805-815. 10.1086/503848. Retrieved from https://hdl.handle.net/10161/21856.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Kathleen M. Pryer
Professor of Biology

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