Phenotypic and genotypic variations in floral traits that affect mating system of Collinsia heterophylla
Student thesis: Doctoral Thesis
This research studied phenotypic and genetic variations in eight floral morphological traits that affect the mating systems of Collinsia heterophylla, effects of pollination treatments on flower longevity and pollen-tube growth rate. The aim was to assess how phenotypic and genetic variations in floral traits, as well as other interacting mechanisms, influence mating systems in plants. This study found that, floral traits varied continuously within - and between - populations, and across floral developmental stages in Norway and Chiltern populations. Floral traits showed high correlations and heritabilities, with corolla, stamen and pistil recording the highest correlations in the two populations. Thereby, suggesting genetic linkages or pleiotropy effects among traits. Consequently, traits either evolve together or the selection of one trait constrains the other. Thus, the termination of pistil life through pollination and fertilisation could impact on structure and functions of the corolla, pistil and the stamens. The study also found that, the effects of pollination treatments, time of pollen arrival and pollination significantly affect flower longevity. Furthermore, autonomous selfing occurred early in Norway population, but late in Chiltern population. Inter-population cross pollination treatment showed shortest flower longevity in Norway population than Chiltern, indicating differential pollen-tube growth rate. Pollen-tube growth rate was assessed in-vitro and in-vivo and results showed no correlation in pollen-tube growth rate invitro and in-vivo. However, Chiltern population had longer pollen-tube growth in-vivo than Norway population. Similarly, Chiltern population grew longer pollen-tubes on the Norway style than on the Chiltern and vice versa in Norway pollen-tubes; suggesting partial cryptic selfincompatibility (CSI) in C. heterophylla. Therefore, floral traits variations, correlations, heritabilities, flower longevity and post-pollination processes can drive the course of mating systems evolution in flowering plants.
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