Origin and Development of Plasma Membrane Derived Invaginations in Vinca Rosea L.

Abstract

The plasma membrane in immature cells is often irregular in contour. Some irregularities become conspicuous folds that continue to enlarge into the cytoplasm. These invaginations may continue to increase in size and typically expand into the central vacuole. Sections show two closely parallel membranes in areas where the invagination projects into the vacuole. A narrow layer of cytoplasm may traverse the intermembrane zone between the membranes. The interior of an invagination may lack obvious content, or may be occupied by a fibrous material, or vesicular and tubular structures. The small vesicles bound by a single membrane appear to be derived from a projection formed most frequently near the orifice of the invagination. The origin of large vesicles and tubules possessing one membrane is not certain although they may arise by the fusion of several small vesicles. Alternatively, tubules, once formed, often possess constrictions along their length which suggest that these structures may become divided into a series of smaller vesicles. There is some evidence that cytoplasmic vesicles may fold into the membrane of the invagination and subsequently be pinched off into the interior of the sac. These vesicles are bounded by two membranes. Vesicles frequently contain an electron‐dense content more or less homogeneous in composition and unlike the typical ribosomal character of the cytoplasm. The function of the invaginations or their content remains to be elucidated.

Localization of Crystals in Diseased Oats Treated with Uranyl Acetate

“…Membranes were frequently concentrically arranged and occurred both within vacuoles and in the cytoplasm adjacent to the plasmalemma. These membranous structures resembled the plasmalemmasomes found in Vinca rosea by Mahlberg et al (9). Since membranous inclusions were rare in water-treated or deactivated toxintreated leaves, they were probably responses to damage by the toxin.…”

“…Unless stated otherwise, all experiments were repeated once. Victorin was produced by procedures previously published (9) and in one set of experiments was dialyzed and desalted with Sephadex G-25. Solution uptake occurred in a growth chamber as a result of transpiration under conditions of continuous light and air circulation.…”

Ultrastructure, composition, and biogenesis of the encapsulation material surrounding the endophyte in Alnus crispa var. mollis root nodules

“…Multivesicular-like bodies, observed in plants, have been related with wall synthesis or degenerative processes (Jensen 1965;Halperin and Jensen 1967;Mahlberg et al 1971 ;Heyn 1971). The suggested mechanism of endophyte capsule biogenesis is similar to cell wall formation and deposition in plants (Esau et al 1966;Gifford and Steward 1967), in fungi (Bracker and Butler 1963;Marchant et al 1967;Peat and Banbury 1967;Held 1972), and in algae (Ramus 1969 It was generally agreed that the process responsible for the encapsulation is a host defense FIG.…”

Small Pathogenic RNA in Plants-The Viroids

“…Observations of the sites of viroid accumulation indicate no changes in nuclear structure; however, the manifestation of vesicular and tubular proliferation is evident in the paramural region (73). The plasmalemmosomes, or endocytic invagi nations from the plasma membrane are not viroid-specifi ed cytopathic structures (40,41). Nevertheless, the increased frequency of these struc tures may refl ect a developmental lesion introduced as a result of viroid infection.…”