Light-induced redistribution of excitation energy in leaves as observed in terms of fluorescence induction

Intact leaves of Phascolus mdgaris were illuminated with strongblue light to induce a transition of pigment states from a highfluorescent state (State I) to a low fluorescent state (StateII), and their fluorescence induction curves were measured atroom temperature and low temperature. The induction curves at –196°C were measured at 692and 730 nm in order to investigate the states of PhotosystemII and Photosystem I separately. At 692 nm, the leaves in StateII showed one level of fluorescence without any variation, F_s,which was approximately the same as the initial F_o level inState I. At 730 nm, however, the F_s level was rather close tothe maximal F_M level in State I. These results are discussed according to the model of photochemicalapparatus of photosynthesis proposed previously and interpretedthat the excitation energy is transferred directly from thereaction centers of Photosystem II to Photosystem I. (Received April 2, 1976; )