AOBPreview published online on June 8, 2007
Annals of Botany, doi:10.1093/aob/mcm085
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Floral Ontogeny of the Afro-Madagascan Genus Mitrasacmopsis with Comments on the Development of Superior Ovaries in Rubiaceae
1 Laboratory of Plant Systematics, K.U.Leuven, Kasteelpark Arenberg 31, PO Box 2437, BE-3001 Leuven, Belgium
2 National Botanic Garden of Belgium, Domein van Bouchout, BE-1860 Meise, Belgium
3 National Herbarium of the Netherlands, Leiden University Branch, PO Box 9514, NL-2300 RA Leiden, The Netherlands
* For correspondence. E-mail inge.groeninckx{at}bio.kuleuven.be
Received: 27 December 2006 Returned for revision: 22 January 2007 Accepted: 13 March 2007
Background and Aims: Members of Rubiaceae are generally characterized by an inferior ovary. However, Mitrasacmopsis is cited in the literature as having a semi-inferior to superior ovary. It has previously been hypothesized that the gynoecial development of Rubiaceae with semi-inferior to superior ovaries takes place in the same way as in Gaertnera, one of the most commonly cited rubiaceous genera with a superior ovary. To test this hypothesis, a floral ontogenetic study of Mitrasacmopsis was carried out with special attention paid to the gynoecial development.
Methods: Floral ontogeny and anatomy of Mitrasacmopsis were examined using scanning electron and light microscopy.
Key Results: At an early developmental stage, a concavity becomes visible in the centre of the floral apex simultaneously with the perianth initiation. A ring primordium surrounding this concavity expands vertically forming the corolla tube (early sympetaly). Stamen primordia develop inside the corolla. From the bicarpellate gynoecium only two carpel tips are visible because the ovary is formed by a gynoecial hypanthium. In the basal part of each carpel, a placenta primordium is initiated. Two septa divide the ovary into two locules. In each locule, the placenta becomes mushroom shaped and distinctly stalked. Eventually, the inferior ovary of Mitrasacmopsis develops into a beaked capsule. Only very late in the fruiting stage, the continuously expanding ovary is raised above the insertion point of the persistent calyx, changing the ovary position of Mitrasacmopsis from basically inferior to secondarily semi-inferior.
Conclusions Mitrasacmopsis: follows an epigynous pattern of floral development. However, the presence of a prominent beak in the fruiting stage gives the whole ovary a semi-inferior appearance. This kind of secondarily semi-inferior ovary is shown to be different from the secondarily superior ovary observed in Gaertnera.
Key words: Mitrasacmopsis quadrivalvis, Gaertnera, floral ontogeny, gynoecial development, epigyny, secondary semi-inferior, secondary superior, scanning electron and light microscopy
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  Compiled by, F. Tooke, T. Chiurugwi, and N. Battey Flowering Newsletter bibliography for 2007 J. Exp. Bot., July 18, 2008; (2008) ern109v1. [Full Text] [PDF]
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