Photosynthetic Mutants Separate Electron Paramagnetic Resonance Signals of Scenedesmus

Current schemes for the mechanism of the photosynthesis reaction imply a two-part cycle; one part produces a strong photoreductant, the other functions to release molecular oxygen. Wild-type Scenedesmus exhibits the two light-induced electron-paramagnetic resonances typical of green algae and chloroplasts of higher plants. These resonances indicate the presence of unpaired electrons in at least two sites. By means of mutants which are blocked in one or the other part of the dual cycle, the narrow, rapidly decaying signal can be correlated with the photoreductant part, and the broad, slowly decaying signal can be correlated with the part releasing molecular oxygen.