We have investigated the cytochrome components and the light-induced absorbance changes at 77°K of chloroplasts isolated from Phaseolus vulgaris greened under intermittent light.

Leaves in which the capacity to evolve oxygen had been induced by a short period of continuous light contained very small amounts of cytochrome b−559_HP. Similar amounts were present in uninduced leaves.

C550 was present in uninduced leaves as well as in all cases where oxygen evolution was possible.

It was concluded that neither cytochrome b−559_HP nor C550 were involved in the induction process.