CHANGES IN STOICHIOMETRY AMONG PSI, PSII AND CYT B(6)-F COMPLEXES IN RESPONSE TO CHROMATIC LIGHT FOR CELL-GROWTH OBSERVED WITH THE RED ALGAPORPHYRA-YEZOENSIS

Stoichiometry among 3 thylakoid components, PSI and PSII and Cyt b(6)- f complexes, was determined with the red alga Porphyra yezoensis with special reference to the regulation of PSI/ PSII stoichiometry in resp onse to light regime. The ratio of PSI to PSII abundance was four time s greater in thalli grown under orange light which excites mainly phyc obilisome, thus PSII, than that under red light which excites preferen tially Chi a, thus PSI. Cyt b(6)-f abundance remained almost constant. The PSI and PSII content was regulated separately under the two growt h light conditions as was also observed with the red alga Porphyridium cruentum by Cunningham et al. [(1990) Plant Physiol. 93: 888]. This d iffers from the cyanophyte Synechocystis PCC 6714 where adjustment occ urs only in the PSI content [(1987) Plant Cell Physiol. 28: 1547]. How ever, results on the marine cyanophyte Synechococcus NIBB 1071 indicat e that changes in the PSI/ PSII stoichiometry is similar to red algae. In this species, as in the red algae, more than one PSII is associate d with each phycobilisome. The light regime also induced changes in th e phycobiliprotein composition in Porphyra yezoensis. Under PSII light , phycoerythrin increased, and phycocyanin decreased, while under PSI light the response was reversed. The change suggests an occurrence of complementary chromatic adaptation.