Comparative development of rare cases of a polycarpellate gynoecium in an otherwise monocarpellate family, Leguminosae.
OBJECTIVE
Apocarpy (i.e., free carpels) is considered to be the basal condition for ovary development in angiosperms. Yet it only occurs in 10% of angiosperm species, of which another 10% are monocarpellate. Most legume flowers are monocarpellate. Species with polycarpellate gynoecia occur in about 15 genera with most representatives in Mimosoideae. In the present study, we analyze legumes with polycarpellate flowers with the aim of improving our understanding of gynoecium evolution.


METHODS
Flowers of nine legume species from five genera were analyzed using a scanning electron microscope (SEM).


RESULTS
In Leguminosae, carpels usually form as individual primordia or protuberances. Inga congesta differs slightly from this pattern in that the central apex bulges outward before the formation of individual carpel primordia. While legumes usually develop entirely plicate carpels, flowers of Acacia celastrifolia and Inga bella show an intermediate type of carpel morphology with a distal plicate zone and a small proximal ascidiate zone. Carpels in Inga congesta and Archidendron glabrum are sometimes slightly fused at the ovary base. The orientation of carpel clefts seems to reflect the floral symmetry. They are directed to the floral center in mimosoids and caesalpinioids, whereas in Swartzia dipetala carpel clefts are oriented to the adaxial side.


CONCLUSIONS
Polycarpelly arose at least seven times independently in Leguminosae. The polycarpellate condition appears to be correlated with polyandry, and in most instances, it is accompanied by a profound change in floral organization from a closed to an open system.
Universidade de São Paulo (USP), Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Pós-Graduação em Biologia Comparada, Av. Bandeirantes 3.900, Ribeirão Preto 14040-901, SP, Brazil.
Juliana Villela
JV
Paulino
Gerhard
G
Prenner
Vidal Freitas
VF
Mansano
Simone Pádua
SP
Teixeira
D005075:Biological Evolution; D007887:Fabaceae / Q000254:growth & development* / Q000648:ultrastructure; D035264:Flowers / Q000254:growth & development* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D013045:Species Specificity
Fabaceae; Leguminosae; floral development; gynoecium; multicarpelly; ontogeny; polycarpelly