McCalla, Dennis Robert (1961) I. Chemical study of necrotic corn mutants. II. Metabolism of a kinin. III. The chemical nature of an insect gall growth factor. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-04102006-135936
The leaves of nec rd (a single gene necrotic maize mutant) become necrotic when they are exposed to light for a few days. Extensive analysis has failed to reveal any difference in chemical composition between leaves of normal plants and of homozygous nec rd plants before any necrotic symptoms are visible (prenecrotic leaves). Treatment of nec rd seedlings with various metabolites (B vitamins, purines, pyrimidines, amino acids, etc.) did not prevent the appearance of necrosis. The rate of photosynthesis of prenecrotic leaves is normal at low light intensities but 20 to 50% of normal at saturating light intensity. C14O2 feeding experiments indicate that the carbon fixing reactions function normally in the mutant. Hill reaction rates are also similar in mutant and normal plants, as is the metabolism of labelled inorganic phosphate. CMU, which specifically inhibits photosynthesis to the extent of about 90%, delays the onset of visible necrotic damage and reduces the severity of subsequent necrotic symptoms. It is suggested that the nec rd lesion is in some reaction associated with photosynthesis and that it causes the accumulation of one or more toxic substances. These lower rate of photosynthesis and damage cell membranes. The necrotic phenotype would appear to be the result of the breakdown of cell compartmentalization.
The kinin, 6-benzylaminopurine (benzyladenine), is converted to a number of low molecular weight materials by senescing leaves of Xanthium pensylvanicum Wall.(cocklebur). A major product is the riboside, benzyladenosine, which has been identified by comparison of its properties with those of benzyladenylic synthesized enzymatically using E. coli nucleoside phosphorylase and by degradative studies. The ribotide, benzyladenylic acid, also appears to be present. Labelled adenylic, guanylic and inosinic acids are produced, as are small amounts of adenine and guanine. Substantial amounts of label are also found in urea and in a ureide. Small amounts of labelled adenylic and guanylic acids are found in the RNA of the leaf, but benzyladenylic acid itself does not appear to be incorporated into RNA in measurable amounts.
Low molecular weight material obtained from excised accessory glands of Pontania pacifica (gall-wasp) promotes the growth of Pontania galls on Salix alba (willow). Paper chromatographic analysis has indicated that uridine, uric acid and two unidentified adenine containing compounds are prominent constituents of this mixture. Uric acid and the two adenine containing compounds substantially increase the growth rate of small galls from which the larva has been removed while uridine has slight growth promoting activity. Various related compounds (e.g. adenosine, adenine and guanosine) also have growth-promoting activity. It appears likely that such compounds play an important role in the growth and development of Pontania galls.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||1 January 1961|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||11 Apr 2006|
|Last Modified:||26 Dec 2012 02:37|
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