Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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Recently, it was hypothesized that pollinator selectivity for large inflorescences has led to the evolution of monocarpic reproduction in agaves. To test this hypothesis, fruit set and stalk length data were collected for six species of paniculate agaves and two species of spicate agaves. Regression results, for all of the paniculate species and for one species of the spicate agaves, showed no significant correlation between fruit set and stalk length. These results do not support the pollinator selectivity hypothesis. The validity of the assumptions was then examined, utilizing the results from hand pollination, pruning, and tie down experiments. These results imply that factors other than pollinator availability might be important in determining fruit set in agaves. In an effort to determine the relative importance of resource and pollinator limitation to fruit set in Agave chrysantha, three treatments were applied to entire plants: (1) natural pollination, (2) natural and hand pollination, and (3) hand pollination. When fruits were collected, there were no significant differences between percent fruit set for the three treatments, implying that fruit set is not limited by the availability of pollinators. When additional plants were pruned to reduce the total number of flowers by approximately one-half, thereby doubling the amount of resources available to each flower, the percent fruit set was twice that for control plants, implying that percent fruit set is energy limited. It is common for plants that exhibit resource limited fruit set to have relatively low fruit-to-flower ratios. This is surprising, since it appears that the resources expended for production of these "excess flowers" could be allocated to fruit maturation and thereby increase fruit production. Four hypotheses explaining the fruit set in Agave mckelveyana are tested. Results from pruning, bagging, and hand pollination experiments indicate that the apparently "excess flowers" do not contribute to fruit production (female fitness). Additional data on nectar production imply that these flowers act primarily as pollen donors and contribute only to male fitness. The importance of pollen donation (male fitness) in determining fruit set is examined for hermaphroditic, monecious, and dioecious plants.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 246-266). Also available on the Internet.

Self-fertilization requires less energetic expenditures than cross-fertilization and benefits from a 50% advantage in its rate of gene transmission. Yet, no plant species is known that reproduces exclusively via self-fertilization, as all appear to maintain a certain outcrossing rate. I test the hypothesis that, under specific circumstances, cross-fertilization provides short-term advantages over self-fertilization in Corydalis sempervirens, a self-compatible winter annual. / Some fitness components of selfed and crossed progeny were compared under different experimental conditions. Crossed progeny derived short-term advantages from both their higher mean individual heterozygosity and their greater genotypic diversity. Overall, they had higher mean fitnesses than selfed individuals (heterosis), especially in favorable environments. Crossed progeny also displayed greater constancy of yield under increasing densities. In all test-environments, the few individuals with highest fitness resulted from outcrossing. However, as a group, crossed offspring did not have higher fitness values than selfed offspring and not all crosses generated progeny with equally high fitness. The fittest individuals were produced in crosses between parents which shared an intermediate number of common ancestors.

Thesis (M.S.)--University of Wisconsin--Madison, 1948. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [24]-26).

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 246-266). Also available on the Internet.

Nitrogen fertilizers are extensively used to enhance the growth of biomass crops. This study was conducted to determine the effect of N rates on the biomass yield and quality, and N uptake of several crops. The experiment was conducted at Fargo and Prosper, ND, in 2010 and 2011. The crops studied were forage sweet sorghum [Sorghum bicolor L. Moench], sorghum x sudangrass [Sorghum bicolor var. sudanense (Piper) Stapf.], kenaf [Hibiscus cannabinus L.], and reed canarygrass [Phalaris arundinacea L.]. The different crops constituted the main plots and the nitrogen rates were regarded as subplots. The five N rates were 0, 75, 100, 150, and 200 kg N ha-1. Forage sweet sorghum and sorghum x sudangrass had the greatest dry matter biomass yield. Nitrogen fertilization increased biomass yield for each of the crops. The results indicate that forage sorghum and sorghum x sudangrass have the greatest potential as a feedstock.

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