Does the trimeric form of the Photosystem 1 reaction center of cyanobacteria in vivo exist?

When isolating Photosystem 1 from the thylakoid membranes of cyanobacteria, a multiplicity of photosystem complexes can be encountered, which has not yet been observed in any other phototrophic organisms: After solubilisation of thylakoid membranes with detergents, trimeric, dimeric and monomeric forms of Photosystem 1 can be separated. The question must now be answered, which of the stable Photosystem 1 forms is the functional form in vivo-monomeric or trimeric? The two possibilities are discussed, though we mainly present arguments for the existence of the trimeric form of Photosystem 1 in cyanobacterial thylakoid membranes.