Pollen aperture heteromorphism in Centaurium pulchellum (Gentianaceae)

Abstract

Pollen variations involving the number and position of the apertures are relatively frequent in certain members of Gentianaceae. In this paper the high incidence of pollen variation in Centaurium pulchellum (Sw.) Druce is described. Two other species of Centaurium: C. ameghinoi (Speg.) Druce and C. cachanlahuen (Molina) B. L. Rob were also examined. These two species have 3-colporate or, less frequently, 4-colporate pollen grains, which are the two basic aperture arrangements. However, there are also a variable proportion of atypical grains. Apart from typical 3-zonacolporate grains, C. ameghinoi sometimes has 3-syncolpate or parasyncolpate pollen, while C. cachanlahuen occasionally has 4-colporate grains with short colpi that converge in pairs. C. pulchellum also has 3 or 4-colporate grains, but a high proportion of the pollen grains show a range of different aperture patterns. A total of 13 aperture configurations, including the typical 3-colporate and 4-colporate types, were recorded. The proportion of the different pollen types varied widely between and within individuals. However, the production of atypical grains does not seem to have any notable effect on pollen viability within the species. It is suggested that the wide variation in aperture pattern observed in C. pulchellum may be partially induced by environmental factors.