FREEZE-FRACTURE OF MEMBRANES AT THE INTERFACE BETWEEN VEGETATIVE AND GENERATIVE CELLS IN AMARYLLIS POLLEN

The interface between generative and vegetative cells in Amaryllis pol len consisted of the two parallel plasma membranes of these cells. The paired plasma membranes were highly convoluted with broad lobes bulgi ng into the vegetative cells and narrow indentations projecting into t he generative cells. In thin sections, rows of knobbed projections wer e aligned on the inner surface of the vegetative cell plasma membrane. When these membranes were freeze-fractured, the fracture faces of the vegetative cell plasma membrane showed two distinct domains: a partic ulate fracture face in the lobes and oblique parallel ridges on the in dentations. These two domains may correlate with separate functions. T he lobes with projections appeared to be attached to the vegetative ce ll cytoskeleton and may be involved in movement of the generative cell through the pollen tube. The indentations may function to hold the ge nerative cell in place within its cavity in the vegetative cell. These membrane specializations have been observed separately at the generat ive cell-vegetative cell interface in other species, but not in other cell types. No unusual arrangements of intramembrane particles in the generative cell membrane were observed.