Einfluß von Röntgenstrahlen auf HILL-Reaktion und Photosynthesephosphorylierung bei verschiedener Erhaltung isolierter und fragmentierter Chloroplasten

Abstract

Isolated chloroplasts and chloroplast-fragments of different structural state characterized by electron microscopy were irradiated with X-rays. The resistance of Hill- activity and phosphorylation coupled with ferricyanide is strongly dependent on the structural state of chloroplasts and thylakoids influenced by isolation media or by treatment with hypotonic media or digitonin. Whole chloroplasts are more resistant than free membrane systems without stroma and envelop. If free membrane systems were suspended in media of low salinity (broken chloroplasts) the rate of oxygen evolution and of phosphorylation decreases with a factor of 3.8 or 3.0 respectively after irradiation. Hill- reaction and phosphorylation are suppressed successively by washing the particles in hypotonic media or by treatment with digitonin. However, the sensitivity of oxygen evolution against X-rays remains constant in the washed particles whereas the rate of ATP-formation further decreases. As demonstrated by dose effect curves low intensities of X-rays activated the Hill- activity for all fractions. The results are discussed in relation to the integrity of chloroplasts and the state of membrane (thylakoids) as carrier for the systems of Hill - reaction and phosphorylation.