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Title: Some nucleotide fractions of barley leaves, with special reference to the effects of potassium deficiency
Author: Pethiyagoda, Upatissa
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1959
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Potassium-deficient plants commonly have much higher respiration rates than their high-potassium controls. In view of the evidence that respiratory intensity is largely controlled by the internal level of phosphate acceptors like adenosine diphosphate, an attempt was made to determine whether potassium deficiency does in fact affect the free nucleotide contents of plants in any such manner as would explain the respiratory effect along these lines. Serious difficulties of technique •were encountered in estimating the nucleotides, and these have not been completely satisfactorily overcome. Certain widely used techniques were found wanting in various respects. Precipitation methods involving barium and zinc wore tested on both authentic adenine nucleotides and leaf preparations. These were abandoned, owing principally to variable recoveries of authentic nucleotides and to the presence of large quantities of precipitable impurities in leaf extracts. Precipitation with ethanol, a commonly used method for removing such interfering substances, was found to cause considerable losses of the nucleotides. Selective adsorption of nucleotides by various charcoals was found to induce an anomalous behaviour of AMP as regards its elution position when chromatographed on Dowex-1-chloride. This effect, whose nature is unknown, was a property of all the charcoals tested. Water extraction, following a short pre-immersion in boiling ethanol, was adopted for most of the analyses, but perchloric acid was sometimes used as the extractant; this acid -ma shown to release considerable quantities of bound nucleotides. Analyses of the free nucleotides in leaves of high- and low-potassium barley by chromatography on Dowex-1-Chloride and formate columns furnished no evidence of significant changes therein as a result of potassium deficiency. It is tentatively concluded that the enhanced respiration of potassium deficient barley must be primarily due to factors other than the levels of detectable free nucleotides.
Supervisor: Richards, F. J. ; Gregory, F. G. Sponsor: Government of Sri Lanka
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available