ENERGY-TRANSFER AND CONNECTIVITY IN CHLOROPLASTS - COMPETITION BETWEEN TRAPPING AND ANNIHILATION IN PULSED FLUORESCENCE INDUCTION EXPERIMENTS

Despite the fact that fluorescence induction is a very complicated pro cess, the technique is used to obtain information regarding connectivi ty in photosynthetic systems. The models generally used for the analys is are oversimplified, which in some cases has led to questionable int erpretations. Here we describe the effects of nonlinear loss processes in (pulsed) induction experiments and how they obscure the features a ttributed to large-scale connectivity in chloroplasts. We simulate the fluorescence induction process for finite size domains (1-4 reaction centers per domain) and describe both the trapping process and the gen eration of triplets by a discrete state model. From our numerical calc ulations it is demonstrated that singlet-triplet annihilation is unavo idable when using microsecond pulses for actinic illumination.