Discrimination and characterization of photosystem I- and photosystem II-induced 515-nm absorbance change in chloroplasts I. Dissipation of electric field and related processes

Distinctive characteristics of the photosystem I-induced 515-nmabsorbance change and the photosystem II-induced change wereanalyzed in spinach chloroplasts in the absence of added salt.Two types of changes were distinguished by 3-(3,4-dichloro-phenyl)-1,1-dimethylurea(DCMU), carbonylcyanide m-chlorophenylhydrazone (CCCP) and illuminationwith red or far-red light. Half-recovery time of the photosystem I-induced absorbance changewas shorter than that of over-all absorbance change and wasinsensitive to a low concentration (<0.50 µM) of CCCP. In the presence of DCMU, the 515-nm absorbance change decayedin parallel with the rapid protonation of reduced 2,6-dichloroindophenol(DCIP) or methyl viologen. This indicates that the photosystemI-induced local field is dissipated in the electron transferfrom photosystem I to an electron acceptor. Thus the mechanismin dissipation of electric field formed by photosystem I isdifferent from that induced by photosystem II where rapid protonationof plastosemiquinone anion may be directly involved in fielddissipation (Yamamoto, Y. and M. Nishimura: Plant & CellPhysiol. 18: 293–301 (1977)). (Received December 9, 1977; )