Inhibition of photosynthesis and respiration by substituted 2,6-dinitroaniline herbicides. III. Effects on electron transport and membrane properties of isolated mung bean mitochrondria

Twelve substituted 2,6-dinitroaniline herbicides were shown to interfere with electron transport and phosphorylation in isolated mung bean (Phaseolus aureus Roxb.) mitochondria. Postulated sites of action involved complexes I and II, at or near the flavoprotein associated with the oxidation of exogenous NADH, the alternate (cyanide-insensitive) oxidase, and some step in the phosphorylation pathway. Differences among the various 2,6-dinitroanilines tested were generally quantitative rather than qualitative. All of the 2,6-dinitroanilines inhibited the rate of valinomycin-induced mitochondrial swelling in isotonic KCl within the same concentration range that caused inhibition of state 3 respiration. It is postulated that reduced membrane fluidity, or inhibition of chloride transport, may explain the effects on valinomycin-induced swelling. We propose that the 2,6-dinitroanilines partition into the inner mitochondrial membrane, thereby decrease membrane fluidity, and alter membrane permeability. The resulting perturbations to the structural organization of the electron transport components may be responsible for the apparent multiple-site inhibition of respiration.