Abstract
The structural features of flowers and inflorescences of <i>Petasites hybridus</i> and <i>P. albus</i> 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 <i>P. albus</i>. 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.
Highlights
Petasites hybridus (L.) G., M. et Sch. and P. albus (L.) Gaertn. are native to Europe and north-western Asia (Gibbons and Brough, 1995; Schaffner, 1996)
The above-mentioned species are included in bee plants (Bornus, 1989; Lipiński, 2010). Due to their flowering period (III-V), they can provide a source of early spring pollen and nectar to insects which visit their flowers in large numbers under favourable conditions
In some countries P. hybridus has been completely withdrawn from medical use, while in other countries it is allowed for internal use on the condition that there is a low alkaloid content in the herbal preparation (Sadowska, 2004)
Summary
Petasites hybridus (L.) G., M. et Sch. and P. albus (L.) Gaertn. are native to Europe and north-western Asia (Gibbons and Brough , 1995; Schaffner , 1996). P. hybridus is found more frequently in Poland and it inhabits primarily the southern and north-western parts of our country (Zając and Zając , 2001). Plants of both species grow along stream banks and in moist meadows, forming large clusters (Rutkowski , 1996). The above-mentioned species are included in bee plants (Bornus , 1989; Lipiński , 2010). Due to their flowering period (III-V), they can provide a source of early spring pollen and nectar to insects which visit their flowers in large numbers under favourable conditions. In some countries P. hybridus has been completely withdrawn from medical use, while in other countries it is allowed for internal use on the condition that there is a low alkaloid content in the herbal preparation (Sadowska , 2004)
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