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Title: Compartmentation of indole-3-acetic acid in Pisum sativum L.
Author: Brown, Brian Henry
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1984
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Studies were initiated on the compartmentation of indole-3-acetic acid (IAA) in Pisum sativum cv. Meteor. Particular attention has been given to the biosynthesis and catabolism of IAA in isolated pea chloroplast preparations. By the use of high performance liquid chromatography (HPLC), gas chromatography (GC) and combined gas chromatography-mass spectrometry (GC-MS), data were obtained which provided convincing evidence for the presence of IAA and indole-3-ethanol (IEtOH) in light-grown pea seedlings. HPLC, GC and GC-MS analyses also confirmed IAA as endogenous constituent in pea chloroplast fractions while HPLC and GC provided strong evidence for the presence of IEtOH in chloroplast preparations. IAA breakdown during extraction and purification procedures was also investigated. The catabolism of IAA by pea chloroplasts was investigated using both cell-free systems derived from chloroplast fractions and isolated chloroplast preparations. Experiments with both experimental systems have indicated that the major pathway of enzymic catabolism of IAA in pea chloroplasts is by decarboxyative oxidation. Incubations of isolated chloroplast fractions with [1-14C]IAA resulted in the loss of the carbon-1 as 14CO2. A distinct light-effect on the decarboxylation of IAA was observed. Results of control experiments suggested that a neglible proportion of this catabolism was directly attributable to photo-oxidation. HPLC analyses of extracts from [2-14C]IAA-fed incubations suggested that the major detectable catabolite of IAA decarboxylation by pea chloroplast fractions was indole-3-methanol (IMeOH). The identification of this reaction product was confirmed by GC-MS analysis of a purified extract derived from a crude enzyme preparation incubated with IAA. Preliminary investigations into the possible biosynthesis of IAA by chloroplasts of Pisum sativum were also carried out. Isolated chloroplast suspensions appeared to possess the ability to synthesis [3H]IAA when incubated with [3H]tryptophan. No apparent difference was observed in the amounts of putative IAA formed by chloroplasts incubated in the light and darkness. While an enzymic conversion of 0. 17% [3H]tryptophan to putative [3H]IAA by chloroplast fractions was observed, boiled chloroplast and buffer control incubations resulted in 0. 05% non-enzymic synthesis of [3H]IAA.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available