ULTRASTRUCTURE AND ACID PHOSPHATASE IN PEDICEL ABSCISSION OF HIBISCUS

Pedicel abscission in Hibiscus rosa-sinensis was investigated by light and electron microscopy. During the pre-abscission period endoplasmic reticulum declined somewhat, dictyosomes increased in number and apparent activity, and mitochondria maintained their numbers. The observations suggested that dictyosomal vesicles were migrating to and fusing with the plasma membrane. The enzyme acid phosphatase was associated with dictyosomes and dictyosomal saccules, with small vacuoles and invaginations of the plasma membrane, and in the paramural region between the plasma membrane and the cell wall. Our interpretation is that acid phosphatase, (and probably also the enzymes involved in cell wall dissolution) are transported via an endoplasmic reticulum-dictyosome-vesicle carrier system to the paramural regions of the cell. In more general terms, our observations support the view that the enzymes involved in the cell wall hydrolysis of abscission are synthesized within a compartmentalized, lysosomal system prior to their release and action.