Sökning: "pollen germination"

Visar resultat 1 - 5 av 7 avhandlingar innehållade orden pollen germination.

  1. 1. Pollen Competition as a Target for Sexual Selection in Plants

    Författare :Åsa Lankinen; Biologiska institutionen; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Sexual selection; Pollen tube growth rate; Pollen selection models; Pollen interactions; Pollen competition; Plants; Phenotypic plasticity; Non-random mating; Genotype by environment interactions; Mate choice; Viola tricolor.; Plant ecology; Växtekologi;

    Sammanfattning : 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. LÄS MER

  3. 2. Environmental effects on pollen performance:potential consequences on gene flow

    Författare :Margaret Mollel; Biologiska institutionen; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Plant ecology; siring ability; risk assessment; pollen germination; pollen tube growth rate; Nicotiana alata; morphological markers; Cucumis sativus; Genetically modified crops hybridisation; Växtekologi;

    Sammanfattning : 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. LÄS MER

  4. 3. Pollinator-mediated selection and the evolution of floral traits in orchids

    Författare :Judith Trunschke; Jon Ågren; Nina Sletvold; Allan G. Ellis; Uppsala universitet; []
    Nyckelord :Among-population variation; Ecotype; Field experiment; Floral evolution; Germination; Local adaptation; Orchidaceae; Platanthera bifolia; Phenotypic selection; Pollination; Reciprocal transplant; Trait manipulation; Biology with specialization in Ecological Botany; Biologi med inriktning mot ekologisk botanik;

    Sammanfattning : 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. LÄS MER

  5. 4. Reproductive patterns of birches (Betula spp.) in northern Sweden

    Författare :Stig-Olov Holm; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Reproduction; Betula; seed-quality; seed-set; pollination; pollen-limitation; pollen-competition; tree-line; environmental gradient; seed weight; seedling survival; Semudobia;

    Sammanfattning : 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. LÄS MER

  7. 5. Geographic Variation, Hybridization and Evolution in the Bladder Campions, Silene vulgaris and S. uniflora (Caryophyllaceae)

    Författare :Eva Månsby; Biologiska institutionen; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; chemotaxonomy. Physiology of nonvascular plants; Systematisk botanik; Växtgenetik; Systematic botany; taxonomy; morphology; phytogeography; Plant genetics; Paternal effects; Seed polymorphism; Ecology; Ekologi; Crossing barriers; cpDNA markers; Genetic variation; Hybridization; Post-glacial migration; Allozymes; Silene vulgaris; Silene uniflora; taxonomi; morfologi; kemotaxonomi. Växters fysiologi inte kärlväxter .;

    Sammanfattning : 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. LÄS MER