Pollen morphology of alpine butterworts (Pinguicula L., Lentibulariaceae)

The pollen morphology of Pinguicula alpina, P. arvetii, P. grandiflora subsp. grandiflora, P. grandiflora subsp. rosea, P. hirtiflora, P. leptoceras, P. poldinii, P. reichenbachiana, and P. vulgaris, belonging to the Alpine flora, was studied. The pollen grains, coming from different populations, were investigated using light microscopy and scanning electron microscopy. The pollen size, the shape (P/E ratio), the number of colpori and the exine ornamentation are, for Pinguicula, important diagnostic characters. Pinguicula pollen grains are medium sized (∼30μm), trinucleate, isopolar, radially symmetric. The shape of the grains is variable from oblate spheroidal to prolate spheroidal and they are (4)–5–9–(10)-zonocolporate. The prevalent ornamentation is rugulate–microreticulate, P. alpina has a rugulate–reticulate ornamentation and only P. hirtiflora has a perforate ornamentation. A pollen key, based on micromorphological data, is presented.