Ultrastructural Studies Plasma Membrane Related Secondary Vacuoles in Cultured Cells

Abstract

The plasma membrane of cultured cells of several plant species was observed to possess invaginations, or secondary vacuoles, of variable size in the adjacent cytoplasm. These structures, which occurred in cells at different phases in vacuolation, were very numerous in thin sections of some cells but fewer in others. In vacuolated cells enlarged secondary vacuoles protrude into the primary vacuole but are delimited from the tonoplast by an intermembrane zone of variable width. The plasma membrane at the orifice of an invagination may fuse and detach the secondary vacuole from the membrane to form in the cytoplasm a structure bounded by a single membrane. Complex accumulations of membranes consisting of spherical, tubular, and laminar structures, possibly containing cytoplasm, may develop within secondary vacuoles. Contents of many of these vacuoles arise from folds along its limiting membrane which pinch off into the interior of the secondary vacuole. A fibrous substance, possibly derived from the wall, is present in some secondary vacuoles. Observed folding of the plasma membrane and measurements of membrane width of various organelles and cytomembranes support an interpretation that endocytosis occurs in cultured cells.

Vacuole formation as a result of intracellular digestion: Acid phosphatase localization as associated with plasmalemma-invagination and vacuole formation

“…15,16,42), although this was not pointed out by the authors. Since their growth conditions were not clear, we cannot tell whether their heterophagic vacuole formation was caused by the presence of exogenous protein in the culture medium.…”

“…MAHLBERG el 01. (16) classified vacuoles into two types, primary and secondary vacuoles, and reported that secondary vacuoles were derived from PL-invaginations. However, their "secondary vacuoles" correspond only to the endocytotic vacuoles and they did not realize that the really new vacuoles are formed after the digestion of the endocytotic vacuoles.…”

Secretory Vesicle Formation in Glandular Trichomes of Cannabis Sativa (Cannabaceae)

“…The bands appear to become linearly arranged in the wall as a membrane forms across the somewhat narrowed base of the vesicle. Thereafter, the vesicle detaches from the wall to become a free secretory vesicle in the secretory cavity (Hammond and Mahlberg, 1978;Oliveira and Pais, 1990;Mahlberg and Kim, 1991). The secretory cavity contains numerous such vesicles of different sizes that are formed over a period of time during gland development.…”

“…Procedures employed in this study of glandular trichomes on the bracts of pistillate Cannabis plants grown under greenhouse conditions were described previously Mahlberg and Kim, 1991).…”

Auxin Transport Characteristics and Cellular Ultrastructure of Different Types of Parenchyma

“…Such structures have been widely described in cells of whole plants and cultured tissues (e.g. Mahlberg, 1972;Mahlberg et al, 1974;Marchant and Robards, 1968;Street andWithers, 1974, Wochok, 1973), but no clear, single function has been ascribed to them, although an involvement of elaborations of the plasmalemma and similar cytoplasmic structures with deposition of wall material has frequently been suggested (Esau, Cheadle and Gill, 1966;Halperin and Jensen, 1967;Marchant and Robards, 1968;Cox and Juniper, 1973). The plasmalemma has been implicated as the site of cellulose synthesis (Brown and Montezinos, 1975;Shore and MacLachlan, 1975;Willison and Cocking, 1975).…”