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Document Type

Dissertation - University Access Only

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Plant Science

First Advisor

D.G. Kenefick


Sodium dodecylsufate polyacrylamide gel electrophoresis in combination with ribonucleic acid (RNA/SOS-PAGE) was used to find an explanation for low ribonuclease I (RNase I) activity typically associated with excellent freeze resistance in winter barley. Enzyme purification after crude tissue extraction involved (NH4) 2S04 precipitation, OEAE-anion exchange, both followed by concanavalin A (Con A) chromatography. Purification of the enzymes resulted in the identification of RNases found in the Con A-unbound fraction were unique to the susceptible cultivar that were absent in the resistant cultivar. These RNases were found to be EDTA-insensitive. One RNase found in the Con A-bound fraction, believed to be RNase II, was found only in extracts from the freeze resistant cultivar. RNA/SOS-PAGE of crude extracts from both cultivars of whole shoot, primary leaf and coleoptile tissues showed that bands missing from Dicktoo extract were not found in any of the tissues analyzed. Cold acclimation of tissue (2°C) generally suppressed RNase band intensity and failed to enhance activity that might be traced to an abscisic acid enhancement. Results suggest that lower total RNase activity characteristic of freeze-resistant barley cultivars, compared to freeze-susceptible ones, is explained by a fewer molecular forms of RNase. If conclusively shown to be true, it would indicate that natural freeze selection favors barley plants deficient in a certain RNase gene(s).

Library of Congress Subject Headings

Barley -- Frost resistance
Barley -- Anatomy




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