(2004). We favour this approach in our case above the one by Kramer et al. (2004) because it does not need knowledge of the minimal fluorescence in the light activated state (F 0′). Hendrickson et al. (2004) demonstrated that the results are very similar. The GSK126 nmr quantum efficiency of photochemistry, ΦPSII, equals the Genty parameter ∆F/F m ′ (Genty et al. 1989). The quantum efficiencies for heat dissipation and fluorescence are expressed as the quantum efficiency for fluorescence Φf, the

quantum efficiency for photophysical decay or constitutive Seliciclib NPQ (ΦD) and the quantum efficiency for regulated NPQ (ΦNPQ, i.e. qE). ΦD is considered to be an inherent energy dissipation process that is independent of the (short-term changes in) photon flux, i.e. it summarises that fraction of NPQ that is constantly lost as heat by thermal radiation, non-regarding variances in photon flux. ΦD should be constant. Φf describes the same as ΦD, but for fluorescence. Hendrickson et al. (2004) summed the Angiogenesis inhibitor Φf and ΦD as Φf,D: $$ \Upphi_\textf,D = \Upphi_\textf + \Upphi_\textD = \frack_\textf

+ k_\textD k_\textf + k_\textD + k_\textP + k_\textN \cong \fracF^\primeF_m $$ (1)where k f, k D, k P and k N are the rate constants of fluorescence, constitutional thermal dissipation, photochemical and regulated-non photochemical quenching, respectively, and F′ (minimal fluorescence in the light). Because since Φf is small, ΦD is close to Φf,D. The quantum efficiency of NPQ that is regulated via the ΔpH and the xanthophyll cycle (i.e. via qE) can be expressed as: $$ \Upphi_\textNPQ = \frack_\textN k_\textf +k_\textD + k_\textP + k_\textN \cong\fracF^\primeF_m^\prime

– \fracF^\primeF_m $$ (2)(Hendrickson et al. 2004). We used these equations to calculate Φf,d and ΦNPQ using the data given in Fig. 2. We can see that the photophysical decay fraction of NPQ is larger than the qE-driven part of NPQ. It can be clearly seen that kinetics of ΦNPQ resemble the kinetics in NPQ (Figs. 7, 8), although the amplitude is less pronounced. This is most likely because NPQ is not constrained between 0 and 1 as is ΦNPQ. What is also very interesting is that Φf,D Niclosamide resembles the changes in the functional absorption cross section. This can be more clearly seen when Φf,D is plotted as a function of σPSII. Here it can be seen that a smaller functional cross section coincides with a larger Φf,D. When the same procedure is followed for the stepwise increase in irradiance as shown in Figs. 3, 8, partly different results are obtained: as in the single high light exposure, Φf,D > ΦNPQ and the kinetics of NPQ and ΦNPQ resemble each other closely. However, the relationship between \( \textNPQ_\sigma_\textPSII \) and Φf,D is less clear and no relationship between σPSII and Φf,D exists in the experiment where increasing PF were applied.