SPECTRAL EVIDENCE FOR A NEW PHOTOREACTIVE COMPONENT OF THE OXYGEN-EVOLVING SYSTEM IN PHOTOSYNTHESIS

Abstract
On illuminating chloroplasts with "short-wavelength" monochromatic light that supports oxygen evolution, spectral evidence was obtained for a new photoreactive chloroplast component, provisionally designated C550, which shows a reversible decrease of absorbance with a maximum at 550 mmu. The light-induced absorbance changes in C550 have been separated from those due to cytochromes in the same spectral region.The light-induced decrease of absorbance in C550 appears to be independent of temperature, persisting even at -189 degrees and is therefore likely to be linked to the primary light reaction associated with oxygen evolution in photosynthesis.