Floral biology of Senecio macrophyllus M. BIEB. (Asteraceae), a rare Central European steppe plant

Abstract

Knowledge of the flowering phase and plant pollination ecology is very important for understanding the life history of long-lived perennials. In the case of rare species, the information may have implications for conservation practices. Our studies on flower morphology and blooming biology of the vulnerable plant Senecio macrophyllus M. BIEB. were conducted in situ (flowering, activity of insect visitors) in the largest population in SE Poland and in laboratory (light and scanning electron microscopy). The disc florets open diurnally with most intensive anthesis in the early afternoon and attract insect visitors with nectar and pollen. In highly protandrous disc florets, pollen viability decreases in time, whereas stigma receptivity increases. The upper part of the pistil forms a brush-like pollen presenter, covered with unicellular trichomes with chromoplasts. Pollen presentation lasts 4-11 hours per floret, and 8 days in a single head, the main function of which is to extend the availability of male gamets for reproduction. The number of florets per head, the head size, and the number of pollen grains produced per anther, and the pollen grain viability differed significantly between microsites. The finding indicates that, apart from the biotic factors, abiotic conditions may considerably influence generative reproduction of the species. In the study area, the principal visitors of S. macrophyllus flowers were Hymenoptera, with predominance of Apis mellifera (53.4% of visits). The remarkable share of butterflies (13.9%) recognized as the long-distance moving insects may improve the genetic variability of individuals within a fragmented population. A more detailed study is necessary to explain the role of insect visitors in effective pollination and in gene transfer between patches. The assessment of optimal conditions for the generative reproduction is fundamental for the in situ conservation of this rare species.

Ornamental Representatives of the Genus Centaurea L. as a Pollen Source for Bee Friendly Gardens

“…Otherwise the process of pollen production in C. mollis is less responsive to the environment. Differences in species tolerance to habitat conditions with respect to pollen production were demonstrated previously for Asteraceae species (Denisow, 2006;Czarnecka and Denisow, 2014). Similarly, any factors that affect the nutritional status of a plant may affect the amount and quality of pollen produced.…”

“…The pollen is then presented for insects on the style trichomes. This mechanism of pollen presentation is known as secondary pollen presentation (SPP) and is characteristic of the Asteraceae species (Denisow, 2006;Czarnecka and Denisow, 2014); it has also been observed in other ornamentals, including Solidago x hybrida (Strzałkowska, 2006), Zinnia elegans (Wróblewska and Magacz, 2006), and Ligularia species (Wróblewska and Stawiarz, 2011). The mass of pollen produced per plant and per unit area was found to be directly related to the abundance of blooming.…”

“…The mass of pollen produced per plant and per unit area was found to be directly related to the abundance of blooming. The number of flowers or inflorescences is the major predictor of pollen yield in many species, including Ranunculaceae (Denisow and Bożek, 2006), Euphorbiaceae (Denisow, 2009), and Asteraceae (Denisow, 2006;Strzałkowska, 2006;Wróblewska and Stawiarz, 2011;Czarnecka and Denisow, 2014). Year-to-year variations in the number of head inflorescences developed by particular Centaurea species affected the fluctuation in the total mass of pollen available to insect visitors.…”

The effect of the shape of gaps on microenvironmental conditions and seedling recruitment in Molinietum caeruleae meadows

“…Small and isolated populations may suffer from a low level of genetic diversity and a high risk of individual mortality, frequently resulting in their extinction [8][9][10][11]. On the other hand, Czarnecka and Denisow [12] argued that genetic variability of small populations might be improved by long-distance moving pollinators.…”

Does vegetation impact on the population dynamics and male function in Anemone sylvestris L. (Ranunculaceae)? A case study in three natural populations of xerothermic grasslands

“…The paper is one of a series of monitoring studies of rare and endangered entomophilous species across xerothermic grasslands [43][44][45][46]. The main goal in this study was to define factors that may affect the size of three wild populations of Anemone sylvestris with both a short-and long-term perspective.…”