Graduate Thesis Or Dissertation

 

The translocation of ethephon and its physiological effects on the filbert (Corylus avellena L.) during husk senescence Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/bn999995s

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  • Nut drop in the filbert is a consequence of the senescence of the husk. It is possible to accelerate this process by the application of ethephon (2-chloroethyl)phosphonic acid after the nut has abscised from the base of the husk. This study is an investigation on the physiological effects of the use of this chemical to accelerate husk senescence. By measuring the amount of ethylene evolution following husk treatments of ethephon, it was found that a tremendous increase in the rate of ethylene evolution, which is dependent on the log of the concentration of ethephon used, occurred during the first day. The rate of ethylene evolution from the husks remained high for over 7 days. Translocation studies of ethephon from the leaves to the husk were attempted by using both radioactive tracer and biological methods. Ra- dioautographs of filbert stems following foliar applications of ¹⁴C-ethephon showed accumulations of radioactivity in stem tips, lateral buds and husks. In the biological method, rates of ethylene evolution were compared from (1) husks receiving direct ethephon treatments, (2) husks from branches where both the husks and leaves were treated, (3) husks from branches where only the leaves were treated, and (4) husks from untreated control branches. Results from this study revealed a significantly higher rate of ethylene evolution from husks receiving only a foliar ethephon treatment as compared to untreated controls. This indicated that either ethephon or its active derivative was translocated from the leaves to the husks. Such an increase in ethylene evolution occurred in less than a day following ethephon treatments. From these experiments, it is concluded that rapid translocation of ethephon could be achieved in a source-to-sink manner. The applied ethephon breaks down in the plant, leading to an increase in ethylene evolution, and brings about the acceleration of husk senescence. This conclusion is supported by simple laboratory tests using beans and peas. In both plant species, uptake of ethephon was found to occur via the roots and leaves. Biological effects following ethephon applications were those typical of ethylene treatments. These responses were observed mainly in fast-growing locations which would serve as strong metabolic sinks.
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