Plasmalemma structure in relation to microfibril biosynthesis in Oocystis

Summary The plasmalemma of Oocystis apiculata, W. West when freezeetched has been shown to bear granules of several sizes. At the earliest stage of development the outer face of the plasmalemma of the naked autospore has small (8.5 nm diameter) granules aligned in rows, in pairs. These rows are stacked together forming extensive granule-bands over the plasmalemma surface. The orientation of these granule-bands corresponds exactly to one of the major microfibril directions. Occasionally, the bands are reduced to patches, some of which are at right angles to each other. Banding of granules on the inner plasmalemma face of naked autospores is also seen. During development the plasmalemma is seen to change so that in the final stages it bears reticulate invaginations, the granule bands occurring within them. The significance of the granulebands in terms of cellulose microfibril biosynthesis is discussed.