ABSCISSION IN LEAF AND FRUIT EXPLANTS OF PRUNUS-PERSICA (L) BATSCH

Structural and enzymatic aspects of leaf and fruit abscission in explants treated with exogenous ethylene were studied and compared with those previously observed under field conditions. Light and electron microscopy observations reconfirm that differences in abscission occur in leaf and fruit, and in explants cell separation is accelerated, with a more dramatic degradation of the cell walls. In fruit, digestion starts from the middle lamella, and subsequently extends to the entire parietal mass. In the leaf the process involves the primary cell wall, leaving, at the end, undigested materials. In fruit the lytic activity is sustained by endocellulase, and by exo- as well as endopolygalacturonase. In the leaf only endocellulase activity has been found. Cell enlargement phenomena occur subsequent to abscission zone activation in both leaf and fruit explants, involving the cells of either the separation layer or the adjacent region.