title: Slow Passive Diffusion of Orthophosphate between Intact Isolated Chloroplasts and Suspending Medium.
abstract: Isolated spinach chloroplasts purified by isopycnic centrifugation in density gradients of Percoll were found to be highly intact, to be devoid of extrachloroplastic contaminations, and to retain a high rate of CO(2)-dependent O(2) evolution.When suspended in a medium which avoided rupture of the envelope, intact purified chloroplasts progressively lost their phosphate content by passive diffusion. This led to a slow decrease in the uptake of labeled 3-phosphoglyceric acid or orthophosphate (Pi) and in the rate of CO(2)-dependent O(2) evolution by isolated chloroplasts. Under these conditions, there was a good correlation between the rate of CO(2)-dependent O(2) evolution and the concentration of Pi in the stroma space. Addition of Pi to the suspending medium at a final concentration of 10 millimolar, which counterpoised the slow efflux of Pi from the chloroplasts, slowed considerably the decrease in the rate of CO(2)-dependent O(2) evolution.
authors: Physiologie Cellulaire Végétale, Laboratoire de Biologie Végétale, Département de Recherche Fondamentale, Centre d'Etudes Nucléaires et Université Scientifique et Médicale de Grenoble, 85X 38041 Grenoble Cedex, France.
authors: G
authors: G
authors: Mourioux
authors: R
authors: R
authors: Douce