Arrhenius plots indicate localization of photosynthetic and respiratory electron transport in different membrane regions of anabaena

Photosynthetic and respiratory electron-transport reactions by the blue-green alga, Anabaena variabilis, exhibit a strict temperature dependence in vivo as well as in the cell-free system. The ratio of respiratory oxygen uptake in the dark and oxygen evolution in the light is high after growth at low temperatures (20 °C) and low after growth under optimum temperatures (28 °C). Respiration and photosynthesis show different break temperatures in the Arrhenius plots. Increase of growth temperature yields higher break points for photosynthetic or respiratory electron transport as well. These data are taken as evidence that photosynthetic and respiratory electron transport chains are embedded in different membrane areas.