Similarly one can show that the F(t)/F o response changes (blue solid curve) when the rate constant of the release of DSQ is assumed to be 50-fold higher with k dsq~ 15 μs−1, which would mean the ignorance of DSQ release in a time domain above ~10 μs. Fig. 1 Relative chlorophyll a fluorescence change (closed black diamonds) F(t)/F o of 1 h dark-adapted Arabidopsis thaliana leaf in 100 ns to 10 s time range (logarithmic) upon saturating laser flash (6.2 × 1015 photons cm−2/flash), reproduced from Fig. 2 in Steffen et al.

(2005). Bold red curve is the simulated response F DSQ(t) using a modification of Eq. 1a. The modification accounts for a S 0 (β):S 1:S 2 heterogeneity of 0.2:0.4:0.4 with corresponding rate constants of donor side quenching k dsq = 300, 60, and 7 ms−1, k AB~9 ms−1 and a biphasic decay of QB-nonreducing RCs with rate constants k −nqb~25 and 0.5 s−1 Selleckchem MK5108 and nF v = 1.8. Note that F pl is from (reduced) QB-nonreducing RCs at the fractional size β ~ 0.3/1.8~18%. The red dashed curves (closed triangles, diamonds and squares) are simulations with variable rate constant of quenching recovery (k AB) due to Q A − reoxidation. Parameter values of variable quenching-regeneration (k AB) are indicated at the right-hand side of the respective curves. The blue-colored check details dashed curve shows the F DSQ(t) response

when, at constant k AB (~10 ms−1), k dsq is increased 50-fold (for instance when donor side quenching (DSQ) is ignored). The dashed curves illustrate

the effect of interference between k dsq and k AB on the maximum of F(t)/F o with an increasing disproportion between n\( F_\textv^\textSTF (-)-p-Bromotetramisole Oxalate \) and the maximum of F DSQ(t) with the increase in rate (k AB) of quenching recovery In summary, the quantitative data on laser flash-induced variable fluorescence from the 100 ns to 1 ms time range (Belyaeva et al. 2008) confirming those of others (Steffen et al. 2001, 2005; Belyaeva et al. 2006), need a substantial correction with respect to magnitude of the normalized variable fluorescence associated with single turnover-induced charge separation in RCs of PS II. Their data are conclusive with the involvement of donor side quenching, the release of which occurs with a rate constant in the range of tens of ms−1, and presumed to be associated with reduction of \( Y_\textz^ + \) by the OEC. Open Access This article is distributed under the terms of the Creative Commons Attribution click here noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. References Belyaeva NE, Paschenko VZ, Renger G, Riznichenko GYu, Rubin AB (2006) Application of photosystem II model for analysis of fluorescence induction curves in the 100 ns to 10 s time domain after excitation with a saturating light pulse.