Thesis (M. Sc. (Botany))--Rhodes University, 2000.

No description available.

Traditional methods like pruning and breeding have historically been used in crop production to divert photoassimilates to harvested organs, but molecular biotechnology is now poised to significantly increase yield by manipulating resource partitioning. It was hypothesized that metabolic engineering in targeted sink tissues can favor resource partitioning to increase harvest. Raffinose Family Oligosaccharides (RFOs) are naturally occurring oligosaccharides that are widespread in plants and are responsible for carbon transport, storage and protection against cold and drought stress. Transgenic plants (GRS47, GRS63) were engineered to generate and transport more RFOs through the phloem than the wild type plants. The transgenic lines produced more RFOs and the RFOs were also detected in their phloem exudates. But the 14CO2 labeling and subsequent thin layer chromatography analysis showed that the RFOs were most likely sequestered in an inactive pool and accumulate over time. Crossing GRS47 and GRS63 lines with MIPS1 plants (that produces more myo-inositol, a substrate in the RFO biosynthetic pathway) did not significantly increase the RFOs in the crossed lines. For future manipulation of RFO degradation in sink organs, the roles of the endogenous α-galactosidases were analyzed. The alkaline α-galactosidases (AtSIP1 and AtSIP2 in Arabidopsis) are most likely responsible for digesting RFOs in the cytoplasm and may influence the ability to manipulate RFO levels in engineered plants. Atsip1/2 (AtSIP1/AtSIP2 double-knockout plants) were generated and phenotypically characterized based on seed germination patterns, flowering time, and sugar content to observe the impact on RFO sugar levels. The observations and analysis from these lines provide a basis for further insight in the manipulation of resource allocation between source and sink tissues in plants for future research.

Anatomical and developmental tissue relationships between Arceuthobium spp. endophytic tissues and host vascular tissues were examined by light and transmission electron microscopes. The host-parasite pairs studied were Psudotsuga menziesii/A. douglasii, Tsuga heterophylla/A. tsugense, Pinus sabiniana/A. occidentale, and P. lambertiana/A. californicum. The morphological form and growth characteristics of A. douglasii in different aged host tissues was found to be coordinated with growth and maturation of the host. It is proposed that morphological forms of Arceuthobium endophytic tissue be categorized as (1) primary, (2) diffuse-secondary, or (3) localized-secondary in order to semantically clarify the relationship of endophytic morphology with primary or secondary growth stages of host tissue. In localized-secondary endophytic forms, the parasite integrates with host rays to form multiseriate infected rays. At both the light and electron microscope level, parasite cells can usually be identified by their distinctive chromocentric nuclei and abundant lipid bodies or lipid ghosts. Sinker cells of Arceuthobium have unusual plastids which resemble etioplasts and which do not store starch. Sinker cells have distinctive mitochondria with unusually large nucleoid areas. They have abundant endoplasmic reticulum. Wall/plasmalemma specializations increase the membrane surface area in relation to cell volume in sinker cells. The walls of host and parasite are fused at the middle lamella common to both organisms and the organisms share a common apoplast. Pit-like regions in the fused walls of the host/parasite interface were commonly seen in light microscope studies, although such interspecific pitting is seen less than intraspecific pitting. It was determined that, whereas intraspecific pits are traversed by complete plasmodesmata, interspecific pits had no plasmatic channels, or, only half plasmodesmata on the host side of the pit. In one case a half plasmodesmata was seen on the Arceuthobium side of the host/parasite interface. On the basis of the electron microscope studies of the host/parasite interface it appears that plasmatic connections between host and parasite do not normally occur. Because of this plasmatic isolation it can be concluded that nutrient acquisition does not involve direct flow of nutrients via interspecific symplastic bridges. Therefore, photosynthate, normally housed within phloem cells, must be leaked into the common apoplast of both host and parasite before becoming available for absorption into the parasite symplast. Since host and parasite lack symplastic continuity but share a common apoplast, apoplastically-mobile herbicides should be tested for their ability to accumulate in parasite tissues. Cytopathological effects on the host cells were relatively mild although a significant increase in the ratio of radial to axillary vasculature was noted in infected tissue. Other modifications included a tendency for increased numbers of specialized phloem parenchyma (Strasburger cells) in infected rays. No apparent anomalies were observed in conjunction with host sieve cell structure and development. The structure and ontogeny of healthy P. sabiniana phloem was also studied. It was found that the sieve element reticulum (SER) of mature sieve cells is derived from plastids during the maturation of the sieve cell. After maturation some of the SER membranes seem to disassociate into individual 60 (ANGSTROM) fibrils. These fibrils then reassociate and appear to be condensed into paracrystalline bodies which, in turn, participate in the generation of new membranes in the mature sieve cell. Because of their plastid origin, the SER membranes may have energy transducing and ionic pump capabilities that commonly are associated with plastid membranes. Such specialized functions of SER may contribute to the translocating capacities of sieve cells.

Typescript. / Bibliography: leaves [150]-173. / xiii, 173 l illus., table

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. Includes reprinted article: William P. Wergin, Peter J. Gruber, and Eldon H. Newcomb, "Fine structural investigation of nuclear inclusion in plants", Journal of ultrastructure research, v. 30 (1970), pp. 533-557. Description based on print version record. Includes bibliographical references (leaves 76-89).

Visualization of the transport pathway in barley (Hordeum vulgare) leaves was carried out using a combination of aniline blue and a symplasmically transported fluorochrome, 5,6 carboxyfluorescein (5,6-CF). When applied to a source leaf, basipetal movement of 5,6-CF was observed after 3 h and the fluorochrome front was observed about 3-4cm away from the point of application. The fluorochrome was taken up into the symplasm of the mesophyll and was loaded into the bundle sheath cells and then subsequently the vascular parenchyma and finally into the sieve tubes. In sink leaves, acropetal movement was observed after 3 h and the fluorochrome had moved approximately 3 cm away from the point of application. Unloading of 5,6-CF occurred from all classes of longitudinal veins. Studies on solute retrieval showed that 5,6 CF-diacetate was transferred to xylem parenchyma where it was metabolized. 5,6-CF was then transferred from the xylem parenchyma to the vascular parenchyma cells, and it would appear that thick-walled sieve tubes were the first to show 5,6-CF labeling. Counterstaining with aniline blue demonstrates the presence of plasmodesmata and this suggests a potential symplasmic pathway from the mesophyll to the sieve tubes. Application of 5,6 CF-diacetate revealed a slow symplasmic pathway, which involved transfer of 5,6-CF, which was effected via plasmodesma.

No description available.

Thesis (D. Sc.)--Faculty of Science, University of Adelaide, 1990. / Published works [representing] original research conducted during the various phases of [his] academic development--Pref. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.