Reproductive biology and pollen performance of two species of Campanula with different breeding systems

In populations of the naturalized herb, Campanula rapunculoides L. (Campanulaceae), flowers experiencing low rates of pollen removal lasted significantly longer than flowers that had faster rates of pollen removal. Experimental manipulations revealed that low rates of pollen removal resulted in an extension of the staminate phase. Hand-pollinations in which I varied the size and source of the pollen load indicated that when the number of fertilized ovules within an ovary is low, senescence of the flower is delayed, resulting in an extension of the pistillate phase.;Further studies investigating the effect of pollen source on seed set, using C. rapunculoides, showed that the age of the flower at the time of pollen deposition effected the relative performance of cross- and self-pollen. This appears to result from a loss in the ability of these flowers to slow self-pollen tube growth relative to that of cross-pollen tubes. Investigations into the molecular basis of this age-dependent breakdown of self-incompatibility raises the possibility that the synthesis of a potential S-locus associated protein takes place primarily on young flowers and that the protein may become less effective in older flowers.;A controlled crossing experiment in a population of the native herb, Campanula americana L. (Campanulaceae), revealed large maternal effects for all measures of fruit and seed production. Effects due to the paternal parent explained a significant percentage of the variance in some measures of seed production, but this percentage was smaller than that explained by the maternal parent.;Maternal and paternal parentage, seed weight and the size of the pollen load all effected the performance of C. americana progeny during controlled environment chamber and common garden trials. Maternal effects were present for both seedling and reproductive measures of progeny performance, while paternal effects were detected for all seedling measures. The progeny from fruits receiving high pollen loads significantly outperformed the progeny from fruits receiving low pollen loads for all measures of seedling performance except days to emergence.