Influence of osmolality of the medium on photosynthetic electron transport, proton fluxes and photophosphorylation in isolated thylakoids.

The high osmotic potential inhibition of photosynthetic electron transport was determined to be related to membrane compaction rather than to an effect of primary thylakoid volume changes. Osmotic inhibition of proton fluxes and phosphorylation were entirely due to osmotic inhibition of electron transport. The ATPase activity, the nature of coupling and the rate constant of proton efflux were not influenced by osmotic pressure, while the rate constant and the extent of proton influx were inhibited by osmotic pressure.