ABSTRACT
This chapter describes the relationship between photosynthetic processes and reactions that lead to the emission of Delayed fluorescence (DF) quanta by chlorophyll molecules. It presents the way in which the quantitative characteristics obtained on the basis of the DF signal can be used to assess the physiological state of plants. The intensity of DF changes specifically during continuous illumination of photosynthesizing samples pre-adapted to the dark. DF kinetics during the transition of the photosynthetic machinery from dark- to light-adapted states can be presented graphically by a DF induction curve (IC). DF is emitted by excited chlorophyll molecules of photosystem II (PSII) antenna complexes. DF emission spectra are similar to the emission spectra of chlorophyll a fluorescence, which suggests that in both cases (prompt chlorophyll fluorescence (PF) and DF), photon emission results from radiative deactivation of the first singlet excited state of chlorophyll a molecules belonging to PSII antenna complexes
