Abstract
In terms of flowering ecology, <em>Pulsatilla</em> flowers are classified as “pollen flowers” producing inconsiderable amounts of nectar. The aim of this study was to assess the length of the flowering period in <em>Pulsatilla slavica</em> and <em>P. vulgaris</em> and to investigate the structure of the epidermis of the perianth and generative elements of their flowers. Special focus was placed on the structure of hairs and the distribution of stomata. The weight of nectar released by the flowers of the two <em>Pulsatilla</em> species and the content of sugars in the nectar was also evaluated. In SE Poland, both species flowered for similar periods between the second half of April and the first half of May. The flower life-span of both was determined to be 9–14 days. The lower part of each sepal was observed to be covered by long hairs having cellulose-pectin cell walls of varying thickness. Hairs present on the pistil style are thinner; they may provide some protection against cold and can play a role of a secondary pollen presenter for insects. The bowl-shaped structure of the perianth and the nature of the adaxial surface of the sepal epidermis may facilitate reflection of sunlight into the inner parts of the flower, which may contribute to an elevation of the intraflower temperature. This is particularly important for the functionality of the ovary. The surface of the hairs was seen to be covered by a cuticle ensuring water impermeability. Flowers are visited by honeybees, bumblebees, butterflies, and ants, for which nectar and pollen are the main attractants. Ants, which are regarded as illegitimate flower visitors, were found to cause damage to the androecium. The number of fruits produced in the flowers of both <em>Pulsatilla</em> species was lower than 50% of the number of pistils.
Highlights
The genus Pulsatilla (Ranunculaceae) comprises more than 30 species growing in the Northern Hemisphere, primarily in Europe and temperate Asia, with an eastern occurrence range in Japan
The longest, i.e., almost 2-week, persistence of flowers was noted in cultivars ‘Blue Shadow’ and ‘Roede Klokke’, whereas the life-span of the white flowered cultivar was shorter, on average by 5 days (Tab. 2)
In the present investigation carried out during one growth season, we found that the mean weight of nectar produced by 10 P. pratensis and P. slavica flowers was 19.75 mg and 11.0 mg, respectively
Summary
The genus Pulsatilla (Ranunculaceae) comprises more than 30 species growing in the Northern Hemisphere, primarily in Europe and temperate Asia, with an eastern occurrence range in Japan. Species growing in Europe are perennials, characteristic for members of xerothermic communities. Since they have large, decorative flowers, many species are cultivated as early-spring ornamental plants with P. vulgaris subsp. Decorative flowers, many species are cultivated as early-spring ornamental plants with P. vulgaris subsp. In Poland, there are six native Pulsatilla species growing in different habitats: P. alba, P. patens, P. pratensis, P. slavica, P. vernalis, and P. vulgaris. All these species are strictly protected but P. vulgaris probably no longer grows in natural sites in Published by Polish Botanical Society
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