Multiplication and protein content of chloroplasts ofAcetabularia mediterranea in blue light after prolonged irradiation with red light

Summary Cells ofAcetabularia mediterranea were irradiated for three weeks with red light and were subsequently transferred to blue light of equal quantum flux density. Blue light induces protein and chlorophyll synthesis. The chloroplasts multiply intensively between the 8th and 24th hour in blue light and within that time the chloroplast number doubles.Plastid protein, thylacoid protein, nonplastidal protein and chlorophyll are strongly correlated. This means, that their relative proportions do not change under the different light regimes used (white, blue and red light). Possible mechanisms being responsible for the inhibition of chloroplast divisions in red light are discussed.The amount of thylacoid protein can not be the limiting factor for reduced photosynthesis in red light.