Developmental and Structural Section
Staedler, Yannick M. , Weston, Peter H. , Endress, Peter K. .
Floral architecture and phyllotaxis in Calycanthaceae (Laurales).
CALYCANTHACEAE are sister to the remainder of the Laurales (magnoliids), which form two clades of three families each: Siparunaceae-Atherospermataceae-Gomortegaceae and Monimiaceae-Hernandiaceae-Lauraceae. A distinctive feature of Laurales is their seeming diversity in floral phyllotaxis. Floral phyllotaxis is, however, well documented only for some Hernandiaceae and Lauraceae: both families show largely whorled floral phyllotaxis. Information about floral phyllotaxis of the other families of Laurales is scanty and sometimes controversial. Floral phyllotaxis appears to be whorled, spiral, or irregular in the Siparunaceae-Atherospermataceae-Gomortegaceae clade and in Monimiaceae s.s.. In Calycanthaceae, floral phyllotaxis of the whole flower has been studied in only a single species: Calycanthus floridus so far. As floral phyllotaxis seems to be so variable in Laurales, a comparative study of floral phyllotaxis of Calycanthaceae including six species of all four genera was undertaken. Spiral floral phyllotaxis following the Fibonacci pattern was found in all species studied. Organ series (sets of organs of the same kind, which appear in a Fibonacci number and which regularly surround the floral centre) were found in all species, especially in inner perianth members, stamens, and staminodes. Transition between vegetative decussate and floral spiral phyllotaxis was found to vary from species to species. Transition between organ types (tepals, stamens, staminodes and carpels) showed irregularities in organ sequence along the ontogenetic spiral during the transition from staminodes to carpels in three of the six species studied. The androecium and gynoecium structure and development, and behavior of floral parts during anthesis were also studied in the six species. We use our results to discuss the morphological interpretation of the described Calycanthaceae-like fossils.
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1 - Universität Zürich, Institut für Systematische Botanik, Zollikerstrasse 107, Zürich, CH-8008, Schweiz
2 - Royal Botanic Gardens, Mrs Macquaries Road, Sydney, New South Wales, 2000, Australia
comparative floral morphology.
Presentation Type: Oral Paper:Papers for Sections
Location: 303/Bell Memorial Union
Date: Monday, July 31st, 2006
Time: 8:30 AM