Figure 4. The photosynthetic electrons are extracted by Fe(III)CN following the Q_B site.

(a) A scheme of the photosynthetic electron flow (horizontal arrows) with exogenous electron acceptors (vertical arrows) and electron flow inhibitors (vertical dashed lines). Double arrows mark additional electron acceptors. (b) Relative photocurrent of thylakoids, measured at a potential of 0.5 V_Ag/AgCl with 3 mM Fe(III)CN, as a function of DCMU concentration, averaged over at least three experiments. The relative photocurrent is the photocurrent measured with DCMU divided by the photocurrent measured without it, as shown in the inset. (c) Relative photoactivity measured with DBMIB (5 μM) with respect to measurements without DBMIB. The columns show (left to right) the relative photocurrent and oxygen evolution rates measured with Fe(III)CN or DCBQ as acceptors and the oxygen consumption rate using MV as electron acceptor. The results error bars represent the s.d. over at least three measurements. (d) Relative photocurrent and photoactivity of Fe(III)CN and DCBQ reduction rates in PSII particles, relative to the respective measurements with intact thylakoids (both at the equivalent amount of 0.1 mg Chl). It is noted that when measured at the equivalent amount of lower chlorophyll concentration such as 0.01 mg Chl, the H₂O to DCBQ activity of the PSII particles was higher than that of intact thylakoids. The error bars represent the s.d. over at least three measurements.