Participation of the g= 1.9 and g= 1.82 EPR forms of the semiquinone‐iron complex, QA−·Fe2+of photosystem II in the generation of the Q and C thermoluminescence bands, respectively

Following illumination at 200 K, the charge recombination reactions and the origin of the thermoluminescence (TL) bands appearing at about 0°C (Q band) and +50°C (C band) in the glow curve were investigated by comparative TL and EPR measurements in DCMU‐treated photosystem II particles. Decay half‐time measurements carried out at −25°C and +25°C, respectively, suggest that the S2state (multi‐line signal) undergoes charge recombination with the g= 1.9 form of the semiquinone‐iron complex, QA−·Fe2+, resulting in the appearance of the Q band, and that the g= 1.82 form of QA−·Fe2+back‐reacts with the oxidized tyrosine, YD+(Signal IIs), accounting for the generation of the C band.