Department of Basic Sciences, H.P. Agricultural University, Solaa-173230 (H.P.)
The total and ortho dihydroxy (O.D.) phenols increased during cell expansion period, decreased sharply prior to the onset of ripening and increased slightly again during ripening. Peroxidase activity showed two peaks with first peak appearing within 2 weeks of fruit set when cell expansion stage was in progress and the second peak coinciding with the onset of ripening. IAA oxidase activity paralleled peroxidase throughout the period of fruit development. During the first peak, IAA oxidation is prevented due to the presence of phenolic-type auxin protectors and during the second peak the concentration of auxin protectors decreased and IAA oxidase of peach peroxidase catalyzed the oxidation of IAA, that represses ripening of fruits. New isoenzymes of peroxidase appeared during first and second peaks of peroxidase.
