Figure 2. Ability of three quinone derivatives to deplete electrons from Q_B°⁻ and/or PQ²⁻ in the WT strain using chlorophyll fluorescence analysis.

(a) Effect of quinone derivatives on the ratio of initial fluorescence in the presence of 10 μM DCMU (F_i) to that in its absence (F₀) (mean±s.d.; n=3). Addition of DCMU induces a rise of the initial fluorescence level that reflects the residual electron accumulation in the Q_B site or the plastoquinone pool in the dark. (b) Stern–Volmer plot of the maximum fluorescence yield (F_M) showing the fluorescence quenching effect of exogenous quinones (mean±s.d.; n=3). F_M([Q]=0) represents the F_M value in the absence of quinones.