LE3 .A278 2008

2008

Good-Avila, Sara

Acadia University

Bachelor of Science

Honours

Biology

Biology

Genetic self-incompatibility (SI) is a widespread breeding system in angiosperms that prevents hermaphroditic individuals from self-fertilizing. The perennial herb Campanula rapunculoides has been shown to have a gametophytic SI system, whereby incompatible (self) pollen tubes are degraded inside the style. Its SI system is also highly plastic, with expression affected by both genetic and environmental factors. This has important implications for population dynamics in natural environments, as variable expression of SI may allow smaller populations of C. rapunculoides to survive under conditions prohibited by strict SI. The first objective of this study was to further characterize the incompatibility reaction in C. rapunculoides by using timed pollinations on plants with previously characterized SI phenotypes. Pistils were paraffin-embedded and stained using fluorescent DAPI and aniline blue to examine sperm nucleus division during pollen tube growth in relation to the SI reaction. Secondly, hand pollinations were performed on 99 individuals from natural populations of variable size to determine if levels of selffertility, inbreeding depression, autogamous and outcrossed seed set differ between small, medium and large populations of C. rapunculoides. By observing the pollen tube growth and generative cell division across incompatibility phenotypes, it was determined that the SI reaction occurs during the autotrophic-heterotrophic growth transition of pollen tubes, which occurs between 8 and 10 h post-pollination. Exploratory data analyses revealed that the effect of size and population identity significantly affected open pollination seed set. This research will contribute to the understanding of the effect of population size, age and fragmentation on inbreeding depression and breeding systems evolution.

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https://scholar.acadiau.ca/islandora/object/theses:532