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

There are several types of quenching coefficients currently in use which de scribe the decrease of the chlorophyll fluorescence: the photochemical quen ching coefficients q(P) and q((P)rel) and the non-photochemical quenching c oefficients q(N), q((N)rel) and NPQ. These five coefficients were calculate d for a broad variety of cases of the fluorescence signals in a normal, rea listic range and for determining the limits in a range with extremely low a nd high fluorescence values. The calculations showed that the quenching coe fficients currently in use are not only numbers between 0 and 1 as one woul d expect when taking them as a relative measure of the quenching process. M ost quenching coefficients must be regarded and interpreted carefully separ ated from each other. Each photochemical quenching coefficient and each non photochemical quenching coefficient describe the same fluorescence signal i n 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 energ y de-excitation from the photochemical to the non-photochemical route.