A freeze-etch study of membranes in Plasmodiophora-infected and non-infected cabbage root hairs

Abstract

Membranes in cabbage root hairs infected by Plasmodiophora brassicae Wor. and in non-infected cabbage root hairs were investigated by the freeze-etching technique after glutaraldehyde fixation and glycerination. Non-infected root hair membranes were characterized for the first time by freeze etching, and their features were generally similar to those of membrane systems in other cell types. Plasmalemmasomes were observed in infected and in non-infected root hairs to have particle-free fracture faces. Similar fracture faces occurred in the outermost membrane of the envelope surrounding young amoebae in the root hairs; but, the plasma membranes of parasite cysts bore particles, and these showed an unusually strong tendency to adhere to the inner fracture face. In view of this new evidence the possible origin of the amoebal envelope is discussed. Striking developmental changes which occur in the interfacial membranes during the first 21 h of parasite growth are described and discussed.