[Microsecond delayed Chlorella fluorescence]

The kinetics of delayed fluorescence between 40 microseconds and 500 microseconds at room temperature, excited by nanosecond light pulses of a nitrogen laser was analysed in terms of exponential components due to the different ways of reduction of the oxidized reaction centre pigment of the second photochemical system of photosynthesis. The details of the laser phosphoroscope of 20 microseconds resolution time are given. The delayed fluorescence of intact samples has 30 microseconds and 150 microseconds components; treatment with DCMU causes quenching, the kinetics remains unchanged; hydroxylamine causes enhancement at lower concentrations and quenching at higher ones, the component of 150 microseconds disappears. These changes corrborate the heterogeneous center model of the microsecond delayed fluorescence.