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Title: Distribution of endogenous gibberellins in etiolated broad bean (Vicia faba) seedlings
Author: Imam, Ragaa Mohamed
Awarding Body: University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1977
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Abstract:
The work involved here was undertaken as an attempt to extract, purify, fractionate, separate, and identify the endogenous gibberellins in the etiolated broad bean (Vicia faba) seedling. Following a series of preliminary experiments, it was decided to extract the gibberellins in each organ of the seedling separately by ice-cold absolute methanol and fractionate this solvent extract into three fractions, for rough separation of the gibberellins, as follows: i. Free gibberellins or acidic ethyl acetate-soluble fraction. ii. Conjugated-gibberellins or acidic butanol-soluble fraction. iii. Bound-gibberellins or water-soluble fraction. Both the conjugated-gibberellins and the bound-gibberellins were released by acid hydrolysis. The term bound-gibberellin is used here for those gibberellins which appear neither in the acidic ethyl acetate-soluble fraction nor in the acidic butanol-soluble fraction and which are extracted by ethyl acetate at low pH upon hydrolysis. The term does not imply that I have any proof of binding to specific molecules or cell particles. The studies carried out in this thesis revealed that PVP slurries, PVP column chromatography followed by TLC of the gibberellins recovered from the columns effluents are satisfactory tools for the purification and separation of the endogenous gibberellins in the different organs of the etiolated Vicia seedling. During the study, use has been made of both bioassay and GLC following TLC. Peaks with retention time corresponding to the methyl esters of gibberellins A7, A9, A13, A15, A17, and A 24 were detected in the acidic ethyl acetate-soluble fraction obtained from the radicle tissue extracts after raethylation; that obtained from the plumule tissue extracts gave peaks with retention time corresponding to the methyl esters of gibberellins A12, A13, iso-A 13, A24; while the acidicethyl acetate-soluble fraction of the cotyledons tissue extracts gave peaks with retention time corresponding to the methyl esters of gibberellins A3, A5, A 6, A7, A12, A13, iso-A13, A14, and A15. The free gibberellins released by acid hydrolysis of the conjugated-gibberellins in radicle extracts after methylation gave peaks with retention time corresponding to the methyl esters of gibberellins A9, A12, A 13, A14, A20, and A24; those released from the conjugated-gibberellins of the plumule gave peaks v/ith retention time corresponding to the methyl esters of gibberellins A8 and A15; while the free gibberellins released in the case of the cotyledons tissue extracts gave peaks with retention time corresponding to the methyl esters of gibberellins A13 and A14. On the other hand, acid hydrolysis of the bound-gibberellins in the radicle tissue extracts released gibberellins which after methylation gave peaks with retention time corresponding to the methyl esters of gibberellins A7 , A9, A17, and A24 those released from extracts of the plumule tissue gave peaks with retention time corresponding to the methyl esters of gibberellins A7, A8, A 9, A12, and A24 while the free gibberellins released by acid hydrolysis of the cotyledons bound-gibberellins gave peak with retention time corresponding to the methyl ester of gibberellin A13. The cotyledons which are the main storage organs in broad bean contain a number of gibberellins in a "bound"? and/or a conjugated form. These gibberellins appear to release free gibberellins on germination. The possible sites of gibberellin metabolism is discussed on the basis of the results obtained.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.460326  DOI: Not available
Keywords: Botany
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