Floral structure and development in Rafflesiaceae with emphasis on their exceptional gynoecia

Autor(en): Lachezar A. Nikolov, Yannick Städler, Sugumaran Manickam, Jürg Schönenberger, Peter K. Endress, Elena M. Kramer, Charles C. Davis
Abstrakt: Premise of the study: The holoparasitic plant family Rafflesiaceae include the world's largest flowers. Despite their iconic status, relatively little is known about the morphology and development of their flowers. A recent study clarified the organization of the outer (sterile) floral organs, surprisingly revealing that their distinctive floral chambers arose via different developmental pathways in the two major genera of the family. Here, we expand that research to investigate the structure and development of the reproductive organs of Rafflesiaceae. Methods: Serial sectioning, scanning electron microscopy, and x-ray tomography of floral buds were employed to reconstruct the structure and development of all three Rafflesiaceae genera. Key results: Unlike most angiosperms, which form their shoot apex from the primary morphological surface, the shoot apex of Rafflesiaceae instead forms secondarily via internal cell separation (schizogeny) along the distal boundary of the host-parasite interface. Similarly, the radially directed ovarial clefts of the gynoecium forms via schizogeny within solid tissue, and no carpels are initiated from the floral apex. Conclusions: The development of the shoot apex and gynoecium of Rafflesiaceae are highly unusual. Although secondary formation of the morphological surface from the shoot apex has been documented in other plant groups, secondary derivation of the inner gynoecium surface is otherwise unknown. Both features are likely synapomorphies of Rafflesiaceae. The secondary derivation of the shoot apex may protect the developing floral shoot as it emerges from within dense host tissue. The secondary formation of the ovarial clefts may generate the extensive placental area necessary to produce hundreds of thousands of ovules.
Organisation(en): Department für Botanik und Biodiversitätsforschung
Externe Organisation(en): Harvard University, Universität Zürich (UZH), University of Malaya
Journal: American Journal of Botany: the journal for all plant biologists
Band: 101
Seiten: 225-243
Anzahl der Seiten: 19
ISSN: 0002-9122
DOI: https://doi.org/10.3732/ajb.1400009
Publikationsdatum: 02-2014
Peer-reviewed: Ja
ÖFOS 2012: 106042 Systematische Botanik, 106008 Botanik, 106012 Evolutionsforschung
Schlagwörter
ASJC Scopus Sachgebiete: Plant Science, Ecology, Evolution, Behavior and Systematics, Genetics
Link zum Portal: https://ucrisportal.univie.ac.at/de/publications/16197f47-af9d-46fc-ab47-c9e9cf116a4b