The ecological features of flowers and inflorescences of two species of the genus Petasites Miller (Asteraceae)

The structural features of flowers and inflorescences of Petasites hybridus and P. albus were compared. Only individuals producing flower heads with male flowers and few female flowers were found in the studied populations. Light microscopy (LM) and scanning electron microscopy (SEM) were used for examination. The present study shows that the stems of the above- -mentioned species differed in height and number of flower heads, but the number of flowers per head was similar. Larger flowers were found on the stems of P. albus. The following features has been found to play an important role in pollination ecology: the strongly contrasting colours of the floral parts; on the petals, the occurrence of several types of cells which can increase the attractiveness of the flowers by refracting sunlight in a different way; production of odorous oils by the petal cells; production of significant amounts of pollen offered to insects by the well-developed pollen presenters; the development of nectaries and nectar production by the male flowers as well as the development of colour attractants by the corolla, anthers, and bracts