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 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. This revised version was published online in August 2006 with corrections to the Cover Date.