Excitation energy transfer between pigment system II units in blue-green algae

Efficiency in excitation energy transfer from closed to open reaction center II in blue-green and red algae was estimated by the method developed by Joliot and Joliot (C.R. Acad. Sci. (1964) 258, 4622--4625) after slight modification; the number of open reaction centers II was counted from the mean O2 yield of repetitive short flashes. The efficiency in energy transfer in Chlorella pyrenoidosa was the same in our measurement as that reported by Joliot and Joliot (0.55 +/- 0.02). However, the values obtained with four blue-green algae and one red alga were very small, in a range of 0.00--0.07. The low efficiency was always obtained independently of the size of the apparent photosynthetic unit which was varied by growth conditions. Results indicated that pigment system II forms a unit in which only one reaction center II is operative.