Deblading of the peach leaf induces petiole abscission at the petiole/shoot junction. The abscission zone (AZ), distinguishable only after deblading, has ca. 10 layers of cells, which undergo significant ultrastructural modifications in that polysomes, dictyosomes, and rough endoplasmic reticulum profiles increase. Cell walls swell and show areas of lysis through the entire parietal region. The cell wall fractures, and the cell disintegrates. Ultrastructural changes in the AZ are paralleled by increases in soluble proteins and in cellulase and polygalacturonase activities. The abscission pattern of the leaf differs from that of the fruit in peach.