School of Botany - Theses

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Author: Blaz�, Kevin L. × Type: Masters Research thesis ×

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    The estimation of indole-3-acetic acid
    Blaz�, Kevin L. (University of Melbourne, 1979)
    This project evolved from a consideration of polarity in the embryo of the brown alga, Hormosira banksii. It was hypothesized that uneven distribution of auxin due to unilateral illumination led to the protrusion of the rhizoid on the dark side of the zygote. It was intended to test this hypothesis by supplying the zygotes with labelled indole-3-acetic acid and, after incubation in this medium, examine the zygotes using micro-autoradiography. The concentration of indole-3-acetic acid in the cell had to be determined in order that the radioactive compound could be supplied to the zygotes at physiological concentrations. This required the review and selection of extraction, purification and assay methods. The literature review encompasses examples of most of the types of methods in current use. Since the various methods of bioassay have many advantages, limitations and equipment requirements in common, only two methods are described. As the same can be said for other types of methods, these are not considered in detail. The literature review is directed at the researcher seeking a method for the assay of auxin, and, to this end, key references are cited to enable the worker to gain more information. On consideration of the equipment available, the method using the fluorescence of 2-methyl indole-?-pyrone appeared the most suitable. For purification, chromatography using a column of polystyrene resin seemed feasible. Finally, methanol, a widely-used solvent, was selected for extraction. The assay method was examined first, as the quality of extraction and purification could then be determined using the assay. Similarly, the purification was examined prior to the method of extraction. In assessing the capabilities of the methods, many problems were encountered - some peculiar to the equipment used, but several fundemental problems related to the techniques themselves. In fact, considering the findings of this work, it is apparent that the methods of auxin-assay warrant reappraisal with particular respect to losses.