Fluorescence of chlorophyll in photosynthetic systems IV. Induction of various emissions at low temperatures

Abstract

The time course of fluorescence was measured at −196° in spinach chloroplasts, Chlamydomonas reinhardi, Anacystis nidulans, Porphyridium cruentum and Porphyra yezoensis and also at −70° in spinach chloroplasts. The three emissions, F684, F695 and F-1 observed at −196° showed induction. The fluorescence intensities rose rapidly at the onset of illumination and then increased gradually to reach the final steady level. The induction of F695 was more marked than F684, as estimated by the relative magnitudes of the transient component of fluorescence to the total or by the values for “work integral”. The kinetic analysis leads to the conclusion that C f695 (pigment emitting F695) is linked to photoreaction II, and that there is a return transfer of excitation energy from C f695 to C f684 (pigment emitting F684). In spinach chloroplasts, the value of the “work integral” of F695 at −196° was almost equal to that of F684 at room temperature, indicating that the size of the electron pool was not significantly changed by cooling. It was concluded, from the analysis of the behavior of F-1, that in the blue-green and red algae, on excitation of pigment system II, F-1 is mainly excited through the excitation transfer from C f684 to C f-1, and that in spinach chloroplasts and C. reinhardi, the transfer is less significant.