Selective inhibition of photosynthetic reactions by polycations.

Histone inhibits the photosystem 1 activities of isolated chloroplasts. This inhibition can be prevented by prior exposure of the chloroplasts to moderate concentrations of inorganic salts. However, even very high concentrations of inorganic salts will not reverse the inhibition, nor is the inhibition reversed by washing the chloroplasts. Exogenous plastocyanin causes a partial reversal of histone inhibition. Histone inhibits photosystem 1 activity in chloroplasts from a variety of higher plants but is not inhibitory to photosystem 1 in cell-free preparations of several algae. Synthetic polylysines inhibit in the same fashion as histones. Histone causes partial inhibition of indophenol dye photoreduction by chloroplasts. Histone inhibits the activity of photosystem 1 particles prepared from chloroplasts but has little effect on indophenol photoreduction by photosystem 2 particles.