Cytological damage and cell wall modification in cultured apple cells following exposure to pectin lyase from Monifinia fructigena

Cultured apple cells were rapidly injured by pectin lyase (PL) from Monilinia fructigena. Changes in the staining of the plasmalemma and cytoplasm were observed concomitant with the loss of vital staining. Paramural bodies, containing vesicles apparently derived from the plasmalemma, were present at an early stage of injury. Further injury was indicated by pseudoplasmolysis, increased vacuolation and cytoplasmic collapse. Methylated pectin was rapidly lost from the walls of treated cells. However, the gross integrity of the cell walls appeared little changed during the early stages of injury. Cell wall degradation appeared to accompany rather than precede severe injury. ATPase activity was localized by a lead capture method at the plasmalemma of cultured cells. A considerable increase in lead stain within the cytoplasm occurred after PL treatment but it still remained localized at the plasmalemma even in apparently severely injured cells. Freeze fracture replication did not reveal any major modification of the plasmalemma after PL treatment even when considerable injury had occurred.