EFFECTS OF 3,5-DIBROMO-4-HYDROXYBENZONITRILE (BROMOXYNIL) ON BIOENERGETICS OF HIGHER-PLANT MITOCHONDRIA (PISUM-SATIVUM)

The herbicide bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) was teste d on mitochondria from etiolated pea (Pisum sativum L. cv Alaska) stem s. This compound when used at micromolar concentrations (similar or eq ual to 20 mu M) inhibited malate- and succinate-dependent respiration by intact mitochondria but not oxidation of exogenously added NADH. Br omoxynil did not affect the activities of the succinic and the interna l NADH dehydrogenases. Analyses of the effects induced by this herbici de on the membrane potential, Delta pH, matrix Ca2+ movements, and dic arboxylate transport demonstrated that bromoxynil is likely to act as an inhibitor of the dicarboxylate carrier. In addition, bromoxynil cau sed a mild membrane uncoupling at concentrations greater than or equal to 20 mu M. No effect on the ATPase activity was observed.