Chlorophyll fluorescence induction during 0.4 to 200 ms multiple-turnover pulses (MTP) was measured in parallel with O2 evolution induced by the MTP light. Additionally, a saturating single-turnover flash (STF) was applied at the end of each MTP and the total MTP +STF O2 evolution was measured. Quantum yield of O2 evolution during the MTP transients was calculated and related to the number of open PSII centers, found from the STF O2 evolution. Proportionality between the number of open PSII and their running photochemical activity showed the quantum yield of open PSII remained constant independent of the closure of adjacent centers. During the induction, total fluorescence was partitioned between Fo of all the open centers and Fc of all the closed centers. The fluorescence yield of a closed center was 0.55 of the final Fm while less than a half of the centers were closed, but later increased, approaching Fm to the end of the induction. In the framework of the antenna/radical pair equilibrium model, the collective rise of the fluorescence of centers closed earlier during the induction is explained by an electric field, facilitating return of excitation energy from the Pheo- P680+ radical pair to the antenna.

中文翻译：

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封闭的光化学反应中心的可变荧光。

在0.4到200 ms的多次翻转脉冲（MTP）期间测量叶绿素荧光诱导，与MTP光诱导的O2释放同时进行。此外，在每个MTP的末尾都使用了饱和单周转闪蒸（STF），并测量了MTP + STF O2的总释放量。计算了MTP瞬态过程中O2演化的量子产率，并与从STF O2演化中发现的开放PSII中心的数量有关。打开的PSII的数量与其运行的光化学活性之间的比例关系表明，打开的PSII的量子产率保持恒定，而与相邻中心的关闭无关。在诱导期间，总荧光在所有开放中心的Fo和所有封闭中心的Fc之间分配。封闭中心的荧光产量为0。最终Fm中有55个处于关闭状态，但不到一半的中心被关闭，但后来又增加了，接近Fm到归纳结束。在天线/自由基对平衡模型的框架中，感应过程中较早关闭的中心的荧光的集体上升由电场解释，从而促进了激发能从Pheo-P680 +自由基对返回到天线。