The origin of the temperature-induced fluorescence fluctuation in Spirulina platensis: temperature-sensitive mobility of PQ molecules.

Temperature effects on state transitions have been studied in the cyanobacterium Spirulina platensis. At lower temperatures the time to reach completion took longer and the extent of the state transitions was larger. Effects were limited to the temperature range below the phase transition temperature of the membrane lipids. In the presence of the artificial electron acceptor phenyl-1,4-benzoquinone (PBQ) state transitions became completely temperature-independent. State transitions induced by a change in the light climate or in darkness by a switch from aerobic to anaerobic conditions responded similar to temperature; the occurrence of state transitions solely by a change of the temperature has been excluded. Our conclusion is that the temperature-dependent mobility of plastoquinone molecules in the thylakoid membranes is the intrinsic cause of temperature effects on state transitions.