Chromatic Regulation of Photosystem Composition in the Photosynthetic System of Red and Blue-Green Algae

摘要

A chromatic adaptation in the photosynthetic quantum yield for the light mainly absorbed by chlorophylla(Chlalight) first found by Yocum (1951) was studied with one red and three blue-green algal strains. When the cells were grown under a weak Chlalight, the quantum yield in all the strains increased. Comparison of photosystem (PS) compositions, including phycobilin (PBP) and Chlaantennae, reaction centers I and II, in the cells grown under the light mainly absorbed by PBP and Chlarevealed that changes in quantum yield could be attributed to changes in the ratio of PS I/II; PS I/II becomes larger than 1 under PBP light but decreases to 1 in most cases under Chlalight. The change in the PS I/II ratio is due solely to the changes in the PS I population in the cell; PS II remains constant. These results are similar to the intensity-dependent response in PS composition.A common hypothesis for both the chromatic and intensity-induced regulation of PS composition was proposed based on the idea of balance between the electron flow from H2O to NADP driven by PS I and II and the cyclic one driven by PS I.