Photochemical and non-photochemical quenching coefficients of the chlorophyll fluorescence: Comparison of variation and limits

Abstract

There are several types of quenching coefficients currently in use which describe the decrease of the chlorophyll fluorescence: the photochemical quenching coefficients q(P) and q((P)rel) and the non-photochemical quenching coefficients q(N), q((N)rel), and NPQ. These five coefficients were calculated for a broad variety of cases of the fluorescence signals in a normal, realistic range and for determining the limits in a range with extremely low and high fluorescence values. The calculations showed that the quenching coefficients currently in use are not only numbers between 0 and 1 as one would expect when taking them as a relative measure of the quenching process. Most quenching coefficients must be regarded and interpreted carefully separated from each other. Each photochemical quenching coefficient and each non-photochemical quenching coefficient describe the same fluorescence signal in a different way. Only the relative quenching coefficients q((P)rel) and q((N)rel) match together and can be used to demonstrate a shift of the energy de-excitation from the photochemical to the non-photochemical route.