THE ELSCTROPHOTOLUMINEXCENCE OF CHLOROPLASTS

Delayed light emission emanating from preilluminated chloroplasts can be perturbed with pulsed DC electric fields (200 to 4000 v-cm-1 ).The perturbation produces a strong stimulation of chlorophyll luminescence.During the field perturbation the stimulated emission rises to a maximum, typically within 100 ~s, and then decays.Two kinetic components, R {rapid) and S (slow), are distinguished on the basis of their rise and decay times and their field-dependence.-The R component increases exponentially at high fields, decays within 100 to 300 ~s during the field pul~;e and collapses with t 112 = 15 ~s at the end of the field pulse.The S ::omponent occurs at low fields, exhibits near saturation at 500 v-cm-1 , decay~ with t 112 about 3 ms during the fi~ld pulse, and collapses with t 112 ~ 38 ~s at the end of the field pulse.Studies using inhibitors, ionop1ores, electron donors and electron acceptors associate the R compt.1ent with ion transport processes.'The relation to electron transport associated with Photosystem II is discussed.