Reversible Swelling and Contraction of Isolated Spinach Chloroplasts

Abstract

Sunwiary. Bly uise of a micro technique for prodtucing extracts of spiInach mesophyll cells, chloroplasts were isolated in a state wherein they dlisplaye(l microscopically visible, reversible osmotic properties. Swollein spherical chloroplasts treatedl with hypertonic sucrose or mannitol media, bUt not NaCl, couild be shruinken to a state resembling their disk appearance in livinig cells. Reversible osmotic behavior was more easily demonstratedl when the chloroplasts were initially-isolated from cells in a relatively low osmolar concentration in contrast to uising 0.25 m1 suicrose or more concentrated media. Individual chloroplasts cotuld be swollen and contracted repeatedly throtugh as many as 4 cycles. The relationsh p between the capacity for osmotic behavior and chloroplast appearaince in cell extracts is dliscuissed.In the living higher plant cell, chloroplasts consist of a grantular, chlorophyllouis, stationary lamellar component suirrounded and, presumably, interpenetrated by a pleomorphic mobile phase containing stroma (4,6,21,22

Essential Role of VIPP1 in Chloroplast Envelope Maintenance in Arabidopsis

“…Similarly to the balloon-like structure revealed in this study, swollen spherical chloroplasts were created not only by treating the isolated Col chloroplast with lower osmotic concentration solutions; they could also be shrunk back to their original state when replaced in a solution with hypertonic Suc or mannitol medium (Hongladarom and Honda, 1966). Reversible behavior of this kind is related directly to changes in osmotic pressure inside the chloroplast, which is normally controlled by the inner envelope.…”