Department of Basic Sciences, H. P. Agricultural University, Solan
The total and orthodihydroxy (O.D.) phenols increased during the cell expansion period, decreased sharply prior to onset of ripening and again increased slightly during ripening. Peroxidase activity showed two peaks with first peak appearing during cell expansion stage and second coinciding with the onset of ripening. IAA oxidase activity paralleled the peroxidase activity throughout the period of fruit development indicating that IAA oxidase of apple peroxidase possibly catalyzed the oxidation of endogenous IAA that represses ripening of fruits. During the first peak, IAA oxidation is prevented by the occurrence of high concentration of phenolic-type auxin protectors and with the development of fruit, tissue showed a reduction in the amount of auxin protectors as a result IAA oxidizing capacity of the fruit increased. New isoenzymes of peroxidase appeared corresponding to first and second peaks of peroxidase.
