Die Bedeutung der Photosysteme I und II sowie der oxidativen Phosphorylierung für die lichtorientierte Bewegung des Mougeotia-Chloroplasten

Summary The effects of inhibitors and of uncouplers of the oxidative and of the photophosphorylation, respectively, on the light-oriented chloroplast movements has been investigated. The following results were obtained: 1. The weak-light movement of the induction-type is energetically coupled with oxidative phosphorylation. 2. The weak-light movement under continuous irradiations is governed by ATP produced by oxidative as well as by cyclic photophosphorylation. When inhibiting one of these processes, chloroplast movement only is retarded. Under deficiency of extracellular oxygen the response of movement gets favoured by intracellular O 2 , produced by the watersplitting system of photosystem II. 3. The strong-light movement depends on ATP coming from cyclic photophosphorylation. Neither non-cyclic photophosphorylation nor oxidative phosphorylation seem to contribute ATP to the energetics of this type of movement. 4. At least under strong blue-light the cyclic electron-transport in Mougeotia -chloroplasts seems not to be necessarily dependent on the plastoquinone-pool of the electron transport chain. 5. In all investigated types of chloroplast movements in Mougeotia endogenous ATP might be substituted by an application of exogenous ATP, but not at all by ITP, IDP Of AMP. 6. Under anaerobic conditions strong-light movement is completely inhibited already by low concentration of DCMU. It is supposed that this effect does not depend on the energetics of chloroplast movements. It is discussed that oxygen might be an essential factor in an oxidizing regeneration- process of reduced photoreceptors (flavin and/or phytochrome) being active in light orientation of the chloroplasts.