Plant Biol (Stuttg) 2005; 7(2): 195-202
DOI: 10.1055/s-2005-837576
Research Paper

Georg Thieme Verlag Stuttgart KG · New York

Sexual Dimorphism and Gynoecium Size Variation in the Andromonoecious Shrub Caesalpinia gilliesii

A. Calviño1 , C. Carrizo García1
  • 1Instituto Multidisciplinario de Biología Vegetal, Universidad Nacional de Córdoba - CONICET, Córdoba, Argentina
Weitere Informationen

Publikationsverlauf

Received: August 2, 2004

Accepted: February 2, 2005

Publikationsdatum:
11. April 2005 (online)

Abstract

The degree of sexual dimorphism in flowers and inflorescences can be evaluated early in flower development through the study of floral organ size co-variation. In the present work, the gynoecium-androecium size relationship was studied to assess the degree of sexual expression in flowers and inflorescences of the andromonoecious shrub Caesalpinia gilliesii. The co-variation pattern of floral organ sizes was compared between small and large inflorescences, under the hypothesis that inflorescence size reflected differential resource availability. Also, staminate and perfect flowers were collected from three populations and compared on the basis of gynoecium, ovule length, filament length, pollen size and number. The obtained results indicated that staminate and perfect flowers differed only in the gynoecium and ovule length, whereas filament length, pollen size, and number varied across populations. The gynoecium size was smaller and its variability was much higher in staminate than in perfect flowers, as explained by a recent hypothesis about pollinator-mediated gynoecium size selection acting upon perfect flowers. The analysis of the gynoecium-androecium size relationship during flower development, revealed a dissociation of gynoecium growth relative to other floral structures in some buds. Lower gynoecium-androecium regression slopes and smaller gynoecia length characterized smaller inflorescences, thus reflecting the fact that sexual expression was more male-biased. This trend is in agreement with a differential resource-related response at the inflorescence level, however, post-mating resource allocation and the inclusion of other modular levels may also help us to understand the variation in sexual dimorphism in this species.

References

A. Calviño

Instituto Multidisciplinario de Biología Vegetal
Universidad Nacional de Córdoba - CONICET

Vélez Sársfield 299 C.C.495

X5000JJC, Córdoba

Argentina

eMail: anacalv@imbiv.unc.edu.ar

Editor: J. T. M. Elzenga

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