Cherry Fruit Abscission: Peroxidase Activity in the Abscission Zone in Relation to Separation1

Abstract

Abstract Peroxidase activity was demonstrated in the abscission zone and adjacent tissues of sour cherry fruit (Prunus cerasus L., cv. Montmorency) from Stage I of fruit growth to maturity. Activity was markedly greater in the receptacle and abscission zone, than in the fruit tissues. A difference was observed histochemically in the peroxidase of the abscission layer from that of the adjacent tissues. Moreover, peroxidase activity in the abscission zone increased to a maximum at a stage of development coinciding with the initiation of the separation phase. This increase in activity was accompanied by an increase in 2 of the major isoenzymes and the appearance of a third. The relationship between changes in peroxidase and abscission in fruit explants was less clear. Ethylene and ethephon had no significant effect on total peroxidase activity; however, ethylene appeared to increase the activity of a basic isoenzyme. Cycloheximide treatment decreased total and isoenzyme activity. Lowering the endogenous ethylene level did not reduce total activity, although the activity of a basic isoenzyme was decreased.