[Ultrastructural localization of photosystem I and II active sites in chloroplasts in situ]

Activities related to photosystem I and photosystem II are cytochemically localized at the electron microscope level by using suitable artificial electron donors and acceptors with, or without, factors uncoupling the light-induced electron flow between the two systems. Photo-oxidation of DAB, insensitive to DCMU, is linked to photosystem I activity. It occurs within the grana and stroma membranes of the chloroplasts. Photo-reduction of TC-NBT sensitive to DCMU, is a photosystem II mediated reaction. It is trapped within the grana membranes.