Ascorbic Acid Oxidase in Barley Roots

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Abstract
Ascorbic acid oxidase has been identified by its various properties in the homogenates of barley roots. The retention of activity with the cell wall fragments as the pH of extraction varies, the optimal pH range of external solution for oxygen uptake by root segments supplied with ascorbic acid, and the recovery of activity after plasmolysis of the barley roots affirm, the previously reported association of ascorbic oxidase with the cell walls of various plants. About 90% of the total activity resides in the cell wall fraction of root homogenates. Both plasmolysis and salt solutions decrease the recovery of activity with the cell wall fraction to about 70%. No evidence was found to suggest that the wall-bound activity was due to cytochrome oxidase or that cytochrome oxidase was present in the cell wall fraction of root homogenates.