Search for dissertations about: "pollen germination"
Showing result 1 - 5 of 7 swedish dissertations containing the words pollen germination.
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1. Pollen Competition as a Target for Sexual Selection in Plants
Abstract : According to the theory of sexual selection, traits can evolve because they confer a mating advantage in competition with members from the same sex. In animals, sexual selection is considered as an important evolutionary force. In this thesis I have investigated the potential for sexual selection in plants. READ MORE
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2. Environmental effects on pollen performance:potential consequences on gene flow
Abstract : This thesis illustrates the effects of environmental factors on pollen performance and its importance on gene flow. Pollen competitive ability between the wild and cultivated species of four genera belonging to Cucurbitaceae family was compared to evaluate the evolutionary potential for selection on pollen tube growth rate. READ MORE
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3. Pollinator-mediated selection and the evolution of floral traits in orchids
Abstract : In this thesis, I combined manipulations of traits and pollination environment with analysis of phenotypic selection to examine causes of variation in strength and mode of selection on floral traits, and I conducted a reciprocal sowing experiment to test for local adaptation in germination success. I tested the following predictions (1) the opportunity for selection, and the strength of pollinator-mediated and net selection increase with increasing pollen limitation, (2) the effects of traits affecting pollinator attraction and traits affecting pollination efficiency are non-additive and this leads to pollinator-mediated correlational selection, (3) the effects of spur length on pollen removal, pollen receipt, and female fitness differ between populations with short-tongued and populations with long-tongued pollinators, and (4) local adaptation at the stage of germination contributes to the maintenance of ecotypes growing in grasslands and woodlands, respectively. READ MORE
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4. Reproductive patterns of birches (Betula spp.) in northern Sweden
Abstract : The aim of this thesis was to study patterns of reproduction of Betula pendula and B. pubescens coll. along an altitudinal, coastal-inland, gradient in northern Sweden. The altitudinal variation was related to the distribution of the birch taxa along the gradient. READ MORE
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5. Geographic Variation, Hybridization and Evolution in the Bladder Campions, Silene vulgaris and S. uniflora (Caryophyllaceae)
Abstract : In the present thesis, I investigated the inter- and intraspecific variation in the Silene vulgaris/uniflora species-complex (the bladder campions). I have focused on the effects of past and present hybridization both on a large scale ? over the whole of Europe ? and on a local scale. Silene vulgaris and S. READ MORE