Analyse structurale et architecture de l'inflorescence des Begoniaceae

Abstract

The inflorescence structure of Begoniaceae was analyzed taking into account their degree of symmetry. Qualitative and quantitative analyses of 71 species led to the recognition of nine architectural models. When the whole plant is considered, the inflorescence of Begoniaceae is a thyrse. Comparative analyses of the models allowed to determine at what level symmetry or asymmetry is found. There is a correlation between the total lengths of axes and between flower numbers on the best and least developed sides of an inflorescence. For the whole family, the difference between the two sides of the inflorescence is significant for the former, and not for the latter. Divergence angles on the best developed side do not differ from those on the least developed one for a same ramification, and likewise between successive levels of ramification. Thus, the inflorescence appears asymmetrical if total length of axes is considered. These results tend to support the hypothesis that the Begoniaceae are fundamentally asymmetrical. Inflorescence symmetry is found in some groups by stabilization and compensation of different asymmetric components at the global and local levels. Nevertheless, inflorescence asymmetry does not seem to be related to plant architecture, although it seems to be related to the degree of foliar asymmetry. Key words: Begoniaceae, inflorescence, cyme, inflorescential architecture, structural asymmetry.