Advances on Photosystem II Investigation by Measurement of Delayed Chlorophyll Fluorescence by a Phosphoroscopic Method¶

Abstract

A method for data acquisition based on recording of light signal from a conventional phophoroscope fluorometer with high-speed digitalization is proposed to extract more information from a delayed chlorophyll a fluorescence (DF) signal. During the signal processing from all points registered by the fluorometer, we obtain simultaneously a large number of induction curves of DF decaying at different time ranges. In addition, it is possible to register a series of dark relaxation kinetics of DF, recorded at different moments during the induction period or at different temperatures. This allows the evaluation of the contribution of DF kinetic components during the induction period or at different temperatures and the comparison between DF signals registered with different phophoroscopes. With the phosphoroscope system used in this study, we have shown that the contribution of the millisecond components (with lifetimes 0.6 and 2-4 ms) predominates during the first second of the induction period. After 1 s of illumination, the amplitudes of the 0.6 ms and 2-4 ms components and of the slower one (with lifetime more than 10 ms) become approximately equal. The change in lifetime of the different components during the induction and during gradual heating is also observed. It is shown that all registered DF kinetic components have different temperature dependences.

Kinetics of delayed chlorophyll a fluorescence registered in milliseconds time range

“…Delayed fluorescence dark decays in the time interval from 0.35 to 5.5 ms were measured during dark to light transition using a disc phosphoroscope as described in Zaharieva and Goltsev (2003). The changes of DF features were compared to the variable (prompt) chlorophyll fluorescence (PF) simultaneously registered with the same apparatus and in parallel with Handy PEA fluorometer (Hansatech Instruments Ltd., UK).…”

“…I 2 is usually observed during the PF increase from F i to F P (Goltsev and Yordanov 1997; Zaharieva and Goltsev 2003). This is the time when the reduction of the PQ pool and, consecutively, the disappearance of P 700 + and the decrease of transmembrane electrical gradient begin.…”

Delayed fluorescence in photosynthesis

“…On the contrary, DF has components that decay in very different time domains: in the nanoseconds (Christen et al 2000), microseconds (Jursinic and Govindjee 1977;Jursinic et al 1978;Wong et al 1978;Christen et al 1998;Mimuro et al 2007;Buchta et al 2008), milliseconds (Hipkins and Barber 1974;Barber and Neumann 1974;Zaharieva and Goltsev 2003;Goltsev et al 2005;Buchta et al 2007), seconds Hideg et al 1991;Katsumata et al 2008), and even in the hour time range (Hideg et al 1990).…”

“…There is no consensus nomenclature of the maxima that are observed in the DF induction curve, and no consensus about the number and interpretation of these maxima. Goltsev and coworkers (Goltsev and Yordanov 1997;Zaharieva and Goltsev 2003;Goltsev et al 2005) suggest that the maxima (denoted by I) and minima (labelled as D) should be numbered in sequence according to their position in the IC (I 1 , D 1 , I 2 , D 2 etc. ).…”

“…After about 0.5 s of illumination, because of the reduction of the plastoquinone pool, there is a decrease of the outflow of electrons from Q A -, and the RCs shift to a ''closed'' state ZP 680 Q A -Q B = (phase D 2 ) (Gaevsky and Morgun 1993;Zaharieva and Goltsev 2003;Goltsev et al 2005). Under these conditions, the amplitude of the 160-ls component decreases, and the lifetime of the ms component increases .…”