The rate of epinephrine oxidation in soybean hypocotyl, mitochondria was increased by the presence of respiratory substrates, the oxidation rate was lowered by the addition of SOD. It indicated that single electron reduction of molecular oxygen occured and formed O_2~- during mitochondria respiration. The efficiency of superoxide radical generation in higher plant mitochondria was related to the kind of respiratory substrate and its concentration. Tbe submitochondria had higher rate than mitochondria in the...