Quantitative relationship between two reaction centersin the photosynthetic system of blue-green algae

Abstract

The quantitative relationship between reaction centers I and II was studied with blue-green algae Anabaena cylindrica, Anabaena variabilis and Anacystis nidulans grown under different light conditions. The number of reaction centers I was estimated from the P700 content and that of reaction centers II, from the O2 yield of repetitive short flashes. Supplementary determinations were done with three other blue-green algae and one red alga. The maximum number of reaction centers II counted from the O2 yield of repetitive short flashes was markedly smaller than the total number of P700 in all algae tested when the algae were grown under weak light; in the extreme case (Anabaena cylindrica), the ratio was only 0.258±0.015. This ratio became larger and close to unity when the algae were grown under stronger light. Variation in the number of reaction centers in a single cell suggested that reaction center I was a variable component. Our results indicate that the proportion of the two reaction centers may markedly vary in blue-green algae depending on the growth conditions