Changes in Ulrastructure following Fungal Invasion and the Possible Relevance of Extracellular Enzymes

Changes in fine structure of fruit tissues were examined by electron microscopy for the following host-parasite relationships: Sclerotinia fructigena on apple and pear, S. sclerotiorum on cucumber, and Phytophthora palmivora on egg plant. While S. fructigena caused localized degradation of the wall region, S. sclerotiorum caused extensive wall degradation, and infection by P. palmivora was characterized by disintegration of plasmalemma and tonoplast. These effects appeared to be correlated respectively with pectolytic enzyme activity in vivo with S. fructigenay cellulolytic activity with S. sclerotiorum, and the in vitro lysis of membranes by culture filtrates of P. palmivora.