Theses
Permanent URI for this collectionhttps://repository.ui.edu.ng/handle/123456789/407
Browse
3 results
Search Results
Item AN INVESTIGATION OF SOME HORMONAL BASES FOR ABSCISSION IN COWPEA (VIGNA UNGUICULATA L. WALP.)(1977-05) ADESOMOJU, A. A.The Investigations carried out on the abscission problem in cowpea are reviewed. The Isolation 5 characterization 9 physiological roles, chemistry, biosynthesis and metabolism of the various groups of plant hormones are also reviewed. Using biological assays and combined gas-liquid chromatography- mass spectrometry (GC-MS, some of the hormones in the extensively purified acidic ethyl acetate extracts obtained from 2-day old and 6-day old cowpea fruits were examined. Biological assays indicated the presence of only Inhibitors in the 2-day old fruits but inhibitors as well as gibberellins and auxins were indicated to be present in the 6-day old fruits, GC-MS analysis of the extract from 2-day old fruits afforded the identification of the known inhibitors, abscisic acid and phaseic acid. 6’-hydroxymethyl abscisic acid was also identified in the extract and this is the first reported evidence that 6’-hydroxymethyl abscisic acid occurs naturally. Several plant hormones were identified (GC-MS analysis) in the extract from 6-day old fruits. These were abscisic acid, phaseic acid, dihydrophaseic acid,’1iso1dihydrophaseic acid, 6’-hydroxyinethy abscisic acid; gibberellins A4, A6, A8, ‘iso’ A8,and A20. Gibberellins A1,A5,and A29 were also believed to be probably present. Two components, believed to be two new gibberellins were also identified in the extract and were tentatively called gibberellins X and Y. Tentative structures were assigned to these two new gibberellins. Purified acidic ethyl acetate extract obtained from fruits that were over six days old was also analysed on the GC-MS. The result was essentially similar to that obtained for the extract from the 6-day old fruits. The crude acidic ethyl acetate extracts from 6-day old seeds and the fruit walls of the 6-day old fruits were also examined on the GC-MS. Several gibberellins were tentatively identified in the extract from the seeds but only one gibberellin could be identified in the extract from the fruit walls. The methyl esters of 16α-hydroxy, 17-hydroxy, and 16α, 17-dihydroxy derivatives of gibberellin A34 and the 16-epimers of the last two compounds were synthesized from gibberellin A4. This was done in order to correlate the structures that were tentatively assigned to the two new gibberellins with the natural compounds. The disparity in the hormonal contents of the 6-day old and 2-day old fruits is discussed in relation to the abscission problem in cowpea.Item STUDIES ON THE CHARACTERISTIC pH OF HAEMOGLOBINS(1972-01) ADEOSUN, O. S.The thermodynamics of the azide binding reactions of the hybrids of human and canine haemoglobins (i.e. α2Aβ2Ca and α2Caβ2A) as well as the isolated α and ß polypeptide chains of human and canine haemoglobins have been studied at various pH's and temperatures. Plots of -ΔH° against pH, for all the species, show a distinct maximum. The pH at which the maximum value of - ΔH° occurs is termed the 'characteristic pH' (pH ch). From the results it is concluded that the value of pH ch for the haemoglobin tetramer is an average of the pH ch's of the separate α and ß polypeptide chains although: the form of the curve of -ΔH° against pH is a function of the tetramer and cannot be obtained by averaging -ΔH° values for the individual chains. The Bohr effect of the two hybrids has also been measured and compared with that of the parent haemoglobins. A study of the equilibrium reaction between oxyhaemoglobin and carbonmonoxide was carried out and the accompanying thermodynamic data assessed in terms of the mechanisms postulated for explaining ligand binding reactions of methaemoglobin.Item THE REACTIONS OF SOME ACTIVATED AROMATIC HALIDES WITH PIPERIDINS, AND N-BUTYLANINE IN DIPOLAR APROTIC AND DIPOLAR PROTIC SOLVENTS(1975) ADENLE, M. A.The reactions of 2-chloro-5-nitro pyridine with piperidine have been studied in acetone and in nethanol. In acetone, the rate constants are measured as a function of the anine concentration. In methanol, the Arrhenius parameters are obtained. In methanol, except for a very slight (almost negligible) downward trend of rate constants at very high concentration which is explained in terms of Charge - transfer complexes, there is no base catalysis and the observed rate constants are the rates of formation of the intermediate complex. The rates of reaction of 1-X-2, 4-dinitrobenzene (X=F, Cl) with piperidine and n-butylamine in methanol, acetone, and chloroform (stabilised and destabilised) have been measured as a function of the amine concentration. In acetone, the reactions of both substrates with piperidine show true base catalysis with K3/K2 > 50 in both cases. In Chloroform with n-butylamine, there is very little rate increase with increasing amine concentration. For both Substrates, K3/K2=3. This is explained in terms of hydrogen-bonding in the intermediate state. In methanol, the reaction of the chloro Substrate with piperidine gives a small linear increase of rate constants with increasing amine concentration; while for the fluoro substrate, the graph of rate constants against amine concentration gives a doubly sloped curve. This is due to some special unknown medium effects. In acetone, the reactions with n-butylamine give rather peculiar results. The chloro substrate appears to be more sensitive to catalysis by amine than the fluoro substrate - a Situation hitherto unknown. In general, for the reactions in methanol and Chloroform, there is not much base influence; while those in acetone are dependent on the base strength.