Measurement of the redox state of the ubiquinone pool in plant mitochondria

Abstract
We have investigated the dependence of the respiratory rate on the redox poise of the quinone pool in isolated turnip and pea leaf mitochondria. A linear relationship has been found between these two parameters during succinate oxidation under both state 3 and 4 conditions. When succinate is oxidised by the alternative oxidase the dependence of oxygen uptake on the steady‐state reduction level of quinone is markedly non‐linear. These results are discussed within the frame‐work of a homogeneous quinone pool.