Pollen morphology and its taxonomical implications - case studies on the genera Iris L. (Iridaceae) and Hypericum L. (Hypericaceae)

The aim of this study was to invastigate the taxonomical and evolutionary significance of pollen morphological features. Therefore pollen grains of two different large genera Iris L. (Iridaceae) and Hypericum (Hypericaceae) were studied by scanning electron microscopy. All pollen grains of the genus Iris are sulcate with mainly reticulate ornamentation or rarely with more or less partially semitectate exine, with a variable sculpturing - bacula or gemmae, baculae or gemmae. However, several different pollen types were recognized and taxonomically delimited to the specific subgenera, sections and series levels. Palynological features which could have taxonomical importance on different classification levels are: shape of dry pollen grains, shape, outline and approximate size of hydrated pollen grains, approximate size of the sulcus, ornamentation of the sulcus membrane and of the exine. Possible taxonomic and evolutionary implications of pollen morphology of the genus Iris were suggested on all classification levels. Pollen grains of the genus Hypericum were regularly three-zonocolporate with a microreticulate or reticulate ornamentation pattern. However, some taxa showed some irregularities, they may produce more than three apertures and hence loosed its polarity. Although earlier eleven distinct pollen types , described on the basis of shape, type of endoaperture and ornamentation of exine, according to our results, pollen morphology of the genus Hypericum is phylogenetycally more or less uninformative. Such different taxonomical implications of pollen morphology within two large groups of plants (genera), would indicate type of their phylogeny and evolutionary processes and will be briefly discussed.