Cucurbita maxima and Cucurbita andreana are closely related species; however, the calcium phytate levels of the Cucurbita seeds differ significantly. Hybridization of the two Cucurbita species is difficult to achieve. The aim of my research was to extensively study the structure of C. maxima and C. andreana pollen and determine whether the pollen of the species differed in their elemental content. This thesis entails the most comprehensive study of the structure, chemical composition and elemental content of the pollen from a dicot plant. This study of Cucurbita pollen required the use of various light microscopy, electron microscopy and elemental analyses techniques. Histochemical stains revealed information about the chemical structure of pollen and pollen storage reserves. The primary storage reserve of Cucurbita pollen consisted of starch. Additional storage reserves consisted of protein, small amounts of lipids and mineral reserves. Additional studies of the external and internal structures of the Cucurbita pollen were carried out with transmission electron microscopy and scanning electron microscopy respectively. Preparation of sections of pollen for electron microscopy was difficult. Sectioning problems arose due to the thick pollen wall, the density of pollen cytoplasm, and inadequate infiltration of epoxy resin into pollen during processing. C. maxima and C. andreana pollen grains were fixed anhydrously because water-soluble phytates such as potassium phytate are extracted by aqueous fixatives . The cytoplasm of both species contained many small electron-dense globoid particles. Globoid particles were observed in sections of pollen and in samples of ground pollen. Elemental analysis of globoid particles from Cucurbita pollen was carried out, for the first time, with energy dispersive X-ray (EDX) analysis. EDX analysis spectra of globoid particles from C. maxima and C. andreana pollen were compared. Spectra of Cucurbita pollen globoid particles were similar to spectra from phytate deposits in seeds. EDX analysis of globoid particles of pollen revealed that the globoid particles contained mainly Mg, P and K. EDX analysis spectra of globoid particles of sections of Cucurbita pollen revealed that water soluble materials, likely K phytate, were extracted from sections cut onto water-filled microtome boats. Pollen sections cut onto absolute ethanol-filled microtome boats experienced less extraction of water soluble materials from the sections. Neutron activation analysis of whole pollen grains revealed that the individual concentrations of Mg, K, Ca and P were not significantly different from species to species. The elemental analyses results strongly suggest that phytate is stored in globoid particles of Cucurbita pollen. / Thesis / Master of Science (MS)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/23003 |
| Date | 02 1900 |
| Creators | Skilnyk, Hilary |
| Contributors | Lott, J. N. A., Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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