Chlorophyll a is necessary for oxygen evolution in oxygenic photosynthesis.

Abstract

To understand the function of Chl a in Acaryochloris marina in which Chl d is a major pigment, we measured delayed fluorescence (DF) and estimated a pigment content. A. marina was grown in BG 11 medium under incandescent light with intensities of 5, 15, and 35 μE/(m² sec). DF in the nanosecond time range was measured with a time-correlated single-photon counting method. Pigment content was estimated by HPLC. The DF was observed only in the wavelength region of Chl a both in A. marina and Synechocystis sp. PCC 6803, and the DF completely disappeared by heat-treatment in both species. Analyses on pigment content revealed that the Chl a/Pheo a ratio decreased as decrease in light intensities, but never lowered than one. These clearly indicated that the primary electron donor of the PS II in A. marina is Chl a as in another cyanobacteria.