Sexual dimorphism and gynoecium size variation in the andromonoecious shrub Caesalpinia gilliesii

CALVIÑO A., CARRIZO GARCÍA C.

PLANT BIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2005 vol. 7 p. 195 - 202

1435-8603

The degree of sexual dimorphism in flowers and inflorescences can be evaluated early in the flower development, through the study of the floral organ size covariation. In the present work, the gynoecium/androecium size variation of the andromonoecious species Caesalpinia gilliesii was studied to assess the degree of sexual expression in flowers and its potential dependence on inflorescence length. Staminate and perfect flowers were collected from three populations and compared respect gynoecium and ovules lengths, filament length and pollen size and number. The size covariation of the gynoecium and androecium during floral development was compared between short and long inflorescences. Staminate and perfect flowers differed only in the gynoecium and ovule length, whereas filament length, pollen size and number varied across populations. The analysis of the gynoecium-androecium size relationship during flower development, evinced a dissociation of the gynoecium growth relative to the other floral structures at an intermediate stage of floral development. Shorter inflorescences were more male-biased that longer inflorescences, with a higher gynoecium-androecium dissociation evinced by smaller regression slopes. This trend may reflect a resource related response at the inflorescence level, however, other size relationships operating at the whole plant level may be involved.