Thesis (Ph. D.)--University of Hawaii at Manoa, 2001. / Heading on electronic reproduction: Roberts, Guinnevere Ellen. Includes bibliographical references (leaves 104-131). Also available on microfiche.

Difficulties in pollen transfer have adversely affected seed production of hybrid onion (Allium cepa L.) in the United States. Six onion cultivars were examined for differential attractiveness to the honey bee (Apis mellifera L.). Honey bees clearly discriminated between the onion cultivars in both open plots and caged plots. Nectar secretion, nectar sugar concentration, nectar sugar composition, mectar potassium content, and flower phenology were correlated with honey bee visitation. Nectar secretion rates ranged from 0.54 to 0.84 ul per floret per day. Onion cultivars also demonstrated differential flowering potential. The cultivars produced from 176 to 359 flowers per umbel with 32 to 74 umbels per 30 onions. All onion cultivars examinaed contained viscous nectar with sugar concentrations ranging from 51 to 65% of total dissolved solids. Onion nectar was analyzed by gas chromatography to determine qualitative sugar differences among onion cultivars. All cultivars were hexose dominant with an approximately 1:1 fructose:glucose ratio. However, fructose was slightly more abundant than glucose. Sucrose was much less abundant than the hexose sugars. Atomic absorption spectrophotometry revealed little difference in potassium content among the A. cepa cultivars. Nectar potassium levels ranged from 5,300 ppm to 6,900 ppm. Cultivars with higher nectar potassium levels had fewer honey bee visits. Two honey bee bioassays were conducted. The first bioassay simulated the sugar and potassium composition of each onion cultivar. The honey bees selectively foraged on simulated nectars with low potassium and high sugar concentrations. The second bioassay was designed to test honey bee response to "phenolic-rich" solutions. The natural compounds tested were dilutions of salt cedar (Tamarix pentandra Pall.) honey, almond (Prunus dulcis Mill.) honey, and aloe (Aloe littoralis L.) nectar. The pure synthetic compounds tested were caffeic acid and genestic acid. Generally, honey bees foraged preferentially on the lower phenolic concentrations, indicating that compounds high in phenolic composition inhibit honey bee foraging. Finally, seed yields of each of the cultivars were compared. Wide variations in yields were correlated with honey bee visitation, sugar composition, potassium levels, and flower phenology.

Thesis (Ph.D.) - Simon Fraser University, 2005. / Theses ( Dept. of Biological Sciences) / Simon Fraser University. Includes bibliographical references. Also issued in digital format and available on the World Wide Web.

No description available.

Thesis (Ph. D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 1995? / Includes bibliographical references (leaves 186-209).

Bibliography: leaves 186-209.

Meadowfoam (cultivar Mermaid) is an entomophilous winter annual oilseed crop that has historically produced an average of only two of five seeds per flower. Reference to inadequate meadowfoam pollination exists in the literature, but quantitative evidence is lacking. Studies were undertaken to: 1) quantify meadowfoam pollination requirements and 2) evaluate the potential of an alternative pollinator. In vivo pollination biology studies tested pollen age, stigma age, stylar restriction, and pollen deposition rate effects on seed set. Yield efficacy of Osmia lignaria propinqua Cresson, a native wild bee pollinator, was compared in cages to a honey bee standard and a non-caged honey bee control. Osmia reproductive potential was also tested. Pollen 0-5 days old (postanthesis), stored at 3, 18, or 37°C, did not appear to limit seed set. Stigma age was critical for seed set maximization. Seed set was not influenced by the number of stigmas pollinated per flower, but was limited by less than 25 pollen grains deposited per flower. Seed set and pollen deposition increased with increasing honey bee visits per flower. It was concluded that at least three honey bee colonies per acre should be used for commercial meadowfoam production. Osmia produced comparable individual plant yields to honey bees. Sixty Osmia produced similar solid stand yields to 4000 honey bees. Significantly greater solid stand yields per bee were obtained from Osmia when compared to the honey bee. Osmia survival and female production were negatively correlated with female density, while nest/male/total cell production was positively correlated with female density. Osmia demonstrated yield improvement potential as a meadow-foam pollinator. / Graduation date: 1991

Bibliography: leaves 186-209. / xiii, 209 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 1995

Thesis (M. Ag. Sci)--University of Adelaide, 1987. / Includes bibliographical references (leaves 256-323).

Guayule (Parthenium argentatum Gray) is one of two major plants in the world grown for natural rubber and therefore, is of potential importance to the U.S. One area of research interest relates to methods of enhancing production of viable seeds. Therefore, studies were conducted in 1984, 1985, and 1986, in Tucson, Arizona to determine the effect of honey bee pollination on: seed set; seed weight; total seed yield; percentage of seed germination; yield and percentage of rubber and resin content. This experiment involved four guayule cultivars and four pollination treatments: plants caged with bees; plants caged without bees; plants open-pollinated; and plants individually covered with Delnet bags. All four cultivars responded positively to honey bee pollination. Plots with bees produced at least 195% more seeds than plots from which bees were excluded. However, there were no qualitative differences in the seed weights between the treatments. The percentage of seed germination from plots serviced by bees was significantly greater (65%) than from plots without bees (50%). Highest seed germination rates were obtained when seeds were collected in May (80%) and September (76%). June, July, and August seed collections resulted in lower seed germination rates (40%, 26%, and 63%, respectively). The plots in which bees were present gave a higher rubber yield (323 kg/ha) than plots without bees (255 kg/ha). However, there were no quantitative differences in the percentage of resin content between the treatments. These studies demonstrated that (1) honey bees can increase seed yield, seed germination, and rubber content in guayule, and (2) seeds produced during summer months had poorer germination rates and lower yields.