The ultrastructure of plasmodesmata

Abstract

It is suggested that the central strand which traverses plasmodesmata is in open continuity with the endoplasmic reticulum of adjacent cells, and that this strand (desmotubule) represents a modulation of a normal ER membrane so that it comprises solely spherical protein subunits. This concept is used to illustrate how plasmodesmata could form a median nodule or anastomosing central strands. The implications of this model in relation to current theories of symplasmic transport are discussed, and the possibility for further experimental work is outlined. © 1971 Springer-Verlag.