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Causes of limitation of plant reproduction by pollen and resource availability
Kalousková, Petra ; Janovský, Zdeněk (advisor) ; Sklenář, Petr (referee)
Plant seed production depends on many factors: their life history, the environment they grow in, and other factors such as biotic interactions. However, the immediate cause of the reduction in seed production is the lack of partners or the lack of resources available for seed production. This bachelor thesis aims to summarize and analyze the mechanisms of action and the relative importance of individual causes of limitation of plant seed production. Most plants are pollen limited at least in some seasons or in some localities, in the rest of the situations are plants resource limited. Pollen limitation can be quantitative (low pollen deposition) or qualitative (low quality of pollen). Existing theoretical models of pollen and resource limitation compare use of resources either to attract pollinators (increased flower size, increased number of rewards) and increase the chances of encountering them (change of phenology or prolongation of flowering) or to produce seeds. Plants can sometimes be seemingly pollen limited, with the pollen supplementation increasing seed production at the cost of reducing reproductive effort in the upcoming years. However, the most significant feature of pollination, which is often reflected in the alternation of reduced seed production due to insufficient pollen...
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Reproductive strategies of flowering plants in Afromontane grasslands along an elevational gradient on Mount Cameroon
Anýž, Dominik ; Tropek, Robert (advisor) ; Münzbergová, Zuzana (referee)
in English Montane conditions represent a relatively unfavorable climate for most plants and their pollinators. Consequently, zoogamous plant species growing at high elevations are expected to be pollen limited. According to the "reproductive assurance" and "transmission advantage" hypotheses, such pollen-limited plants will adapt more toward self-pollination than plants in communities with more reliable pollination. To test such predictions, I studied reproduction strategies and pollen limitation of ten zoogamous plant species at three elevations (2,800 m a.s.l. 3,500 m a.s.l. and 4,000 m a.s.l.) in montane grasslands on Mount Cameroon, West/Central Africa. I compared seed sets produces by plants with four treatments in our extensive hand-pollination experiments: autogamy, geitonogamy, outcrossing, and natural control. One experimental species was found to be self-incompatible, six species were partially self-compatible, and one was completely self-compatible and predominantly selfing. In five of these plant species, I compared the reproduction strategies and pollen limitation among the elevations. I found that pollen limitation did rise in two species, we expect this to be due to the fact that the species were already pollen limited at 2,800 m a.s.l. Contrary to the two hypotheses, selfing did...
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Pollination in forest ecosystems
Veljačiková, Hana ; Janovský, Zdeněk (advisor) ; Hadrava, Jiří (referee)
Interactions between plants and their pollinators in temperate forest are different from open habitats. In forest, pollinators are less abundant and this results in frequent pollen limitation of forest understory herbs. Pollinators also need to be adapted for flying in complex stands and for living in unfavorable microclimatic conditions. Floral resources predominantly limit pollinator abundance because of their uneven distribution in space and time. In the present bachelor thesis, I summarize knowledge on pollinator conservation and phenology as well as food resources, microclimate, which together with sufficient nesting options seem to contribute the most to pollinator abundance. Type of forest management is also an important factor, which affects density and diversity of pollinators. Generally, thinning out of trees and removal of understory shrubs have positive effect on flower abundance and benefit pollinators. Factors that influence reproduction success of flowers and pollen transfer distances are further discussed.
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