Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 143-149). Also available on the Internet.

Dissertation (M.S.)--The University of North Carolina at Greensboro, 2008. / Directed by Bruce Kirchoff; submitted to the Dept. of Biology. Title from PDF t.p. (viewed Feb. 2, 2010). Includes bibliographical references (p. 134-146).

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2003. / Thesis documentation sheet inserted. Appendix includes reproductions of four papers and manuscripts, three co-authored with others. Includes bibliographical references. Abstract also available online.

No description available.

Thesis (M.A.)--University of Delaware, 2008. / Principal faculty advisor: Delphis F. Levia, Dept. of Geography. Includes bibliographical references.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 15, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. David Larsen Vita. Includes bibliographical references.

Thesis (doctoral)--Friedricks-Universität Halle-Wittenberg, 1914. / Includes bibliographical references (p. [54]).

The study was aimed at determining the metabolic fate of sucrose in intact sugarcane internodal tissue. Three aspects of the fate of sucrose in storage tissue of whole plants formed the main focus of the work. These were the rate of sucrose accumulation in the developing culm, the characterisation of partitioning of carbon into different cellular organic fractions in the developing culm and the occurrence of sucrose turnover in both immature and mature stem tissues. Specific attention was paid to confirming the occurrence of sucrose turnover in both immature and mature internodal tissue. This sucrose turnover has been described previously in both tissue slices and cell suspension cultures. However, certain results from previous work at the whole plant level have indicated that sucrose turnover does not occur in mature internodal tissue. Radiolabeled carbon dioxide (14CO2) was fed to leaf 6 of sugarcane culms of a high sucrose storing variety (Saccharum spp. hybrid cv. Nco376). All plants were of similar age (12 months) and were grown under similar conditions. The movement and metabolic fate of radiolabeled sucrose was determined at four time points, (6 hours, 24 hours, 7 days and 6 weeks) during a 6 week period. The metabolic fate of sucrose was determined in internodes number 3, number 6 and number 9. Internode 3 was found to have a relatively high hexose sugar content of 42 mg glc&fruc fw g-1 and a low sucrose content of 14 mg suc fw g-1. In contrast the sucrose content of internode 9 was much higher at 157 mg suc fw g-1 and the hexose sugar content much lower at 4.3 mg glc&fruc fw g-1. Based on previous work, the sugar content of internode 3 and internode 9 are characteristic of immature and mature tissues respectively. Internode 6 occupies an intermediary position between internode 3 and 6 with its sucrose content higher than its hexose sugar content, but with the hexose sugar content still being notable at 15 mg glc&fruc fw g-1. Although the metabolic fate of sucrose within sink tissue was the focal point of the study, the experimental design also allowed for certain aspects of sucrose production in the source to be investigated. The average photosynthetic rate for leaf 6 in full sunlight was estimated at 48 mg CO2 dm-2 s -1. During photosynthesis, only 30% of the fixed carbon was partitioned into the storage carbohydrate pool while the remaining 70% was partitioned into sucrose for immediate export from the leaf. This high rate of carbon fixation combined with a high rate of carbon export is characteristic of C4 plants such as sugarcane. On entering the culm, translocation of radiolabeled sucrose was predominantly basipetal with relatively little acropetal translocation. The majority of the radiolabeled carbon was found to be stored in mature internodes. No significant loss of radiolabeled carbon was observed in mature and elongating internodes over the study period. A 22% loss of total radiolabeled carbon was observed in immature internodes over the same period. This can probably be attributed to the higher rates of cellular respiration known to occur in immature tissues. There appear to be three phases of sucrose accumulation in the developing culm. Initially, the accumulation rate in rapidly growing tissue, as internode 3 develops into internode 6, is relatively low. This is followed by a rapid increase in the rate of sucrose accumulation during internode elongation, as internode 6 becomes internode 9. Finally, a decrease in the rate of sucrose accumulation is observed during late maturation, as internode 9 becomes internode 12. Determination of the sucrose content in internodes 3, 6 and 9 revealed that there is a notable increase in sucrose content during internode maturation. It is proposed that the higher sucrose content of mature tissue is not merely a consequence of the longer growth period of mature tissue, but is due to the increased rate of sucrose accumulation observed during internode elongation. Short-term (24 hours) analysis of carbon partitioning revealed that intemodal maturation was associated with a redirection of carbon from non-sucrose cellulal organic fractions to sucrose storage. In immature internodes only 20% of the total radiolabeled carbon was present in the sucrose pool 24 hours after feeding. In elongating internodes the figure increased to 54% while in mature internodes as much as 77% of the total radiolabeled carbon was retained in the sucrose pool. Concomitant with the increased carbon partitioning into stored sucrose down the developing culm is a decrease in carbon partitioning into the hexose sugar pool. In immature tissue, 42 % of the total radiolabel is present in the hexose sugar pool, while in mature tissue the percentage drops to 11%. This decrease is probably indicative of decreased levels of carbon cycling between the sucrose and hexose sugar pool as a result of internode maturation. Internode maturation was also found to be associated with a decrease in the amount of carbon in the water insoluble matter pool and the amino acid/ organic acid/ sugar phosphate pool. Thus, internode maturation is associated with a redirection of carbon from total respiration to sucrose storage. Long-term (6 weeks) analysis of carbon partitioning confirmed that sucrose storage in mature tissue is greater than that in immature tissue. From the 6 hour time point to the 6 week time point, an 87% reduction in the stored radiolabeled sucrose content was observed in immature internodes. During the same period only a 25% reduction in the stored radiolabeled sucrose was observed in mature internodes. Radiolabel loss from the radiolabeled sucrose pool in both mature and immature internodes was accounted for by relative radiolabel gains in other cellular organic fractions. At all time points during the study, and in all three tissues studied, radiolabel was found in the sucrose pool, the hexose sugars pool, the ionic pool and the water insoluble matter pool. The occurrence of radiolabel in the non-sucrose tissue constituents suggests that sucrose turnover is occurring in both immature, and mature internodal tissue. / Thesis (M.Sc.)-University of Natal, Durban, 2000.

The biochemical basis for the regulation of sucrose accumulation is not fully understood. The present study was thus aimed at investigating aspects of 'coarse' (enzyme activity) and 'fine' (metabolite) control of glycolytic enzyme activity in relation to carbon partitioning in the developing stalk (internodes 3 to 10), and between varieties with significant differences in sucrose content. Particular emphasis was placed on studying pyrophosphate: D-fructose-6-phosphate 1-phosphotransferase (PFP, EC 2.7.1.90), since this enzyme has been implicated in sucrose metabolism in other plant species. Within the developing stalk, internodal maturation was associated with a redirection carbon from the insoluble matter and total respiration (C02 production and biosynthesis) to sucrose storage. Between varieties, with significant variation in sucrose content, there was an inverse relationship between hexose monophosphate partitioning into respiration and sucrose. The reduction in carbon flux to respiration was not associated with a decline in the extractable specific activity of PK, PFK and PFP. There was also no alteration in the regulation of PK, PFK and FBPase by change in the mass action ratios. Hexose monophosphate concentration declined approximately two to three-fold from internodes 3 to 9 and Fru-6-P concentration was within the lower Km or 80.5 range (Fru-6-P) of PFP and PFK, respectively (as reported from the literature) . Within the developing stalk, substrate limitation might have contributed to the decline in carbon partitioning to respiration. In sugarcane, the levels of PFP activity were controlled in part by PFP protein expression. 8ugarcane PFP polypeptide(s) are resolved as a single protein with a molecular mass of approximately 72 kO. PFP catalysed a reaction close to equilibrium in all intemodes investigated, and the concentration of Fru-2,6-P2 was shown to be in excess of the requirement to stimulate PFP activity. Carbon flux from the triose-P to hexose monophosphate pool was apparent in sugarcane, suggesting that PFP activity was functional in vivo. The developmental profile of specific PFP activity was not positively correlated to the increasing rate of sucrose accumulation in the top ten internodes of the developing stalk. Between different sugarcane varieties, specific PFP activity was shown to be inversely correlated to sucrose content. / Thesis (Ph.D.)-University of Natal, Durban, 1997.

Mémoire (M.Ress.Renouv.)-- Université du Québec à Chicoutimi, 1993. / Bibliogr.: f. 145-153. Document électronique également accessible en format PDF. CaQCU