Pollen morphology of Campanula (Campanulaceae) and allied genera in Iran with special focus on its systematic implication

Pollen grains of 47 taxa of Campanulaceae including 35 taxa of Campanula that represent its five subgenera and nine sections are investigated. Moreover, five species and three subspecies representing three sections in Asyneuma and one species of each genera Legousia, Michauxia, Zeugandra and Theodorovia were studied by light and scanning electron microscopy. The basic shape of the pollen grains was spheroidal. The apertures vary from tri- to hexa-porate. The sculpturing pattern of exine was rugulate-echinate, rugulate-microechinate or in few species rugulate-microreticulate and microechinate. The most valuable characters for subgeneric classification were the length and density of echini. The length of echini were significantly long (> 2 μm) in C. sclerotricha, Legousia falcata and Michauxia laevigata. Pollen grains show low variation in different species of subgen. Rapunculus, but were variable among different species of some groups, such as sect. Rupestres, probably indicating their non-monophyly despite homogeneity with respect to other morphological characters. Pollen morphology does not support recognition of Asyneuma, Legousia, Michauxia, Symphyandra, Theodorovia, and Zeugandra as separated from Campanula, since none of them exhibit any unique feature.