Morphological diversity of pollen from selected species of the genus Taraxacum, according to their ploidal level

Abstract

The study of the morphology of pollen concerned eight species of the genus Taraxacum. Seven types were chosen with a different number of chromosomes belonging to the section Palustria : Taraxacum paucilobum 2n = 3x = 24, T. subdolum 2n = 3x =24, T. subpolonicum 2n =3x = 24, T. vindobonense 2n = 4x = 32, T. trilobifolium 2n = 4x = 32, T. mendax 2n = 5x = 40, T. portentosum 2n =? and one type from the section Obliqua - T. platyglossum 2n =?. Pollen from all the examined species was observed by SEM microscopy. A distinct relation exists between the morphology of pollen and the way of reproduction. Pollen of triploidal species, being compulsory apomicts, is characterized by a great variability of the size and a high percentage of deformed pollen grains. Tetraploids, being optional apomicts, produce regular pollen with a relatively even size. The regular type of pollen in pentaploidal Taraxacum mendax and in species with an unknown number of chromosomes ( Taraxacum portentosum and T. platyglossum) suggests that these taxa are optional apomicts.