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Abstract Detail


Developmental and Structural Section

Prenner, Gerhard [1], Cacho, N. Ivalu [2], Baum, David A. [3], Rudall, Paula, J. [4].

Exploring the organ–flower–inflorescence boundary in Euphorbia and its allies (Malpighiales: Euphorbiaceae).

The cyathium of Euphorbia and its allies (subtribe Euphorbiinae) closely resembles a bisexual flower with clusters of highly reduced male flowers and a single terminal female.
Detailed comparative investigation of pseudanthia from representatives of all three subtribes of Euphorbieae (Euphorbiinae, Neoguillauminiinae, Anthosteminae) reveals some hitherto unreported features which improve our understanding of the rather complex cyathium: (1) male flowers forming one above the other (instead of the typical zigzag pattern of a cincinnus) in male inflorescences of some Euphorbiinae, (2) perianthlike structures form late in the development of some male flowers of Neoguillauminia cleopatra, (3) an apparently bract-derived female perianth in Anthosteminae and Neoguillauminiinae, and (4) spatiotemporally independent formation of abscission zone and perianth in male and female flowers.
Because of the lack of distinct floral primordia, indistinct boundaries between inflorescence, flower and floral organs demonstrate that neither defining the cyathium as an inflorescence nor as a flower is entirely satisfactory and indicate a ‘hybrid’ flower/inflorescence nature of the cyathium. Based on our current knowledge it is most parsimonious to suggest that the cyathium evolved from a determinate thyrse with a terminal female flower surrounded by dichasial male partial inflorescences.
The hypothesis that the cyathium arose due to reiterated deployment of floral regulatory genes was supported by data obtained using immunolocalization of LEAFY proteins in young cyathia.


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1 - Royal Botanic Gardens, Kew, Jodrell Laboratory, Richmond, Surrey, TW9 3AB, United Kindom
2 - University of Wisconsin, Department of Botany, 430 Lincoln Drive, Madison,, Wisconsin, WI 53706, USA
3 - University of Wisconsin Madison, Department of Botany, Birge Hall, 430 Lincoln Drive, Madison, Wisconsin, 53706-1381, USA
4 - Royal Botanic Gardens, Kew, Jodrell Laboratory, Richmond, Surrey, TW9 3AB, United Kingdom

Keywords:
Euphorbiaceae
Malpighiales
cyathium
LEAFY
Euphorbia
development.

Presentation Type: Oral Paper:Papers for Sections
Session: CP26
Location: Boulevard C/Hilton
Date: Tuesday, July 10th, 2007
Time: 11:45 AM
Number: CP26014
Abstract ID:1232


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