Charging of the A band of thermoluminescence, dependent on the S3 state in isolated chloroplasts.

The intensity of the A band of thermoluminescence from isolated spinach chloroplasts were greatly dependent on the excitation temperature between -40 and -10 degrees C. This dependency was analyzed in relation to the S states in the oxygen-evolving system, and the following results were obtained. 1. The A band was charged only slightly by excitation at low temperature -65 degrees C) with continuous light, but when two flashes had been given before cooling the A band was charged efficiently by the low temperature excitation. 2. The efficiency of the double flash pre-illumination for enhancing the A band showed a steep temperature dependency which agreed with the temperature dependency of the photoconversion from the S2 to S3 state. 3. The A-band-enhancing effect was dependent on the number of flashes, and underwent a quadruple oscillation. 4. The enhancing effect decayed in darkness and the decay course agreed with that of the B1 band but not with that of the B2 band. From these results, the origin of positive charges for the A band was discussed.