Discrimination and characterization of photosystem I-and photosystem II-induced 515-nm absorbance changes in chloroplasts II. Separate local fields in thylakoids indicated by differential responses of the 515-nm absorbance change

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Abstract
Flash-induced 515-nm and 475-nm absorbance changes in spinach chloroplasts were investigated in the presence of 3-(3,4-dichlorophenyl)- l,l-dimethylurea (DCMU). DCMU reduced the magnitude of the 515-nm absorbance change by half and almost completely diminished the absorbance change at 475-nm. The reduction of the 475-nm absorbance change paralleled the inhibition of the photosystem II (PS II) light reaction. When chloroplasts were illuminated with red or far-red light, the ratio of δA515/δA475 changed depending on the photosystem activated. Wide variations in the δA515/δA475 ratio observed in subchloroplast particle preparations were probably due to the enrichment and activation of one of the photosystems. We suggest that the photosynthetic pigments in the thylakoid membrane are heterogeneously distributed, and chlorophyll b molecules that may be responsible for the 475- nm absorbance change are affected by the local field formed by the PS II light reaction. On the other hand, an electric field due to the PS I reaction probably induced the absorbance change at 515-nm