Quelques remarques sur les relations entre morphologie pollinique et polyploidie dans le genre campanula sous-section heterophylla

Abstract

Recent work, in particular cytological studies, concerning the Campanula species belonging to the rotundifolia group, allow one to conclude that these species constitute, in fact, a unit in the process of differentiation. This explains also the difficulties in nomenclature. The palynological data observed under the light microscope are not of interest in this work because of the absence of systematic variation. However, some authors have tried to determine if there could be a relationship between the cytotypes and certain characteristics of the pollen-grain morphology. The diversity of their results has led us to pursue this study with the scanning electron microscope (S.E.M.) on a taxonomically limited material (subsect. Heterophylla (Witasek) Fedorov) collected in only one geographical area (French and Spanish Pyrenees). Pollen grains of Campanula longisepala Podlech, C. recta Dulac, C. ruscinonensis Timbal-Lagrave, C. precatoria Timbal-Lagrave, C. cochlearifolia Lamarck, C. hispanica Willkomm ( C. hispanica ssp. hispanica Willkomm and C. hispanica ssp. catalanica Podlech), C. rotundifolia L., C. scheuchzeri Villars et C. ficarioides Timbal-Lagrave have been examined. The observations drawn from the study show firstly that the sculptures are heterogeneous, secondly that the different types of spines which could be identified do not correspond to the species but rather to the degree of polyploidy. There also appears to be a relationship between the level of polyploidy — whatever the species may be — and the morphology of the spine. This relationship might result from the state of coalescence of the extremities of several lirae.