AOBPreview originally published online on October 2, 2002
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Annals of Botany 90: 579-592, 2002
© 2002 Annals of Botany Company
Study of Homeosis in the Flower of Philodendron (Araceae): a Qualitative and Quantitative Approach
1 Institut de recherche en biologie végétale, Jardin botanique de Montréal, 4101 Sherbrooke Est, Montréal, Canada H1X 2B2, 2 Department of Biology, University of Prince Edward Island, 550 University Avenue, Charlottetown, PEI, Canada C1A 4P3 and 3 Laboratoire de Cytologie Expérimentale et Morphogenèse végétale, Université Pierre et Marie Curie, Bât. N2, 4 place Jussieu, 75 252 Paris Cedex 05, France
* For correspondence. Fax +1 514 8723765, e-mail denis.barabe{at}umontreal.ca
Received: 25 March 2002; Returned for revision: 21 May 2002; Accepted: 15 July 2002 Published electronically: 2 October 2002
This study deals specifically with floral organogenesis and the development of the inflorescence of Philodendron squamiferum and P. pedatum. Pistillate flowers are initiated on the lower portion of the inflorescence and staminate flowers are initiated on the distal portion. An intermediate zone consisting of sterile male flowers and atypical bisexual flowers with fused or free carpels and staminodes is also present. This zone is located between the sterile male and female floral zones. In general, the portion of bisexual flowers facing the male zone forms staminodes, and the portion facing the female zone develops an incomplete gynoecium with few carpels. The incomplete separation of some staminodes from the gynoecial portion of the whorl shows that they belong to the same whorl as the carpels. There are two levels of aberrant floral structures in Philodendron. The first one is represented by the presence of atypical bisexual flowers, which are intermediates between typical female flowers and typical sterile male flowers. The second one is the presence of intermediate structures between typical carpels and typical staminodes on a single atypical bisexual flower. The atypical bisexual flowers of P. squamiferum and P. pedatum are believed to be a case of homeosis where carpels have been replaced by sterile stamens on the same whorl. A quantitative analysis indicates that in both species, on average, one staminode replaces one carpel.
Key words: Inflorescence, development, positional information, sex determination.