MUCILAGE PROCESSING AND SECRETION IN THE GREEN-ALGA CLOSTERIUM .2. ULTRASTRUCTURE AND IMMUNOCYTOCHEMISTRY

We conducted an ultrastructural and immunocytochemical analysis of the subcellular components involved in mucilage secretion in Closterium. In conventionally fixed cells, the mucilage vesicle appears dense-core d with an electron-dense center surrounded by radiating fibrils. In fr eeze-substituted cells, the vesicles are highly osmiophilic. These muc ilage vesicles are produced from peripheral swellings of the trans fac e cisternae of the Golgi apparatus (GA). The vesicles apparently move from the GA, found in cytoplasmic depressions between lobes of the pla stid, to the sub-plasma membrane peripheral cytoplasm. Here, they beco me associated with components of the peripheral cytoskeletal network. The mucilage is ultimately released through flask-shaped pores in the cell wall.