Excitation energy transfer in spinach chloroplasts was investigated by the time-resolved fluorescence spectrum at −196°C with a time resolution better than 10 ps. The characteristic fluorescence bands belonging to each photosystem (PS) were clearly observed. In PS I, two new maxima were found at 690 and 705 nm, both of which showed very short lifetimes, and at least two other fluorescence bands were present at wave-lengths longer than 700 nm. PS II particles showed the maximum at 680 nm just after the excitation pulse. The maximum shifted to 685 nm within 160 ps, and further to 695 nm within 350 ps. The energy flow in each PS was discussed based on the time behaviour of the components.
