EFFECTS OF A QUATERNARY AMMONIUM SALT AND 2,4-D ON POTATO-TUBER MITOCHONDRIA

The effects of a quaternary ammonium salt (AACL 6) and an aryloxyacid (2,4-D) were studied on mitochondria isolated from fresh and aged potato tuber slices. The two compounds seemed to act as inhibitory uncouplers on the electron transport pathway, the quaternary ammonium salt being the most effective. In aged potato mitochondria, resistant to cyanide inhibition, the effects of the two pesticides were investigated on both the cytochrome and alternative pathways. The alternative pathway was found to be more resistant to AACL 6 than the cytochrome pathway. Moreover, studies on the total electron flow in aged potato mitochondria showed that the alternative pathway took over from the cytochrome pathway when the latter was strongly inhibited by AACL 6. This could explain that mitochondria possessing an alternative pathway showed a better resistance to high AACL 6 concentrations. In contrast, 2,4-D rapidly made the alternative pathway inoperative. From swelling measurements in a NH4CI medium, it was shown that the maximal uncoupling AACL 6 concentration is different from D100. Moreover, when swelling was measured in a KCl medium, low AACL 6 concentrations prevented the action of gramicidin and valinomycin, contrary to 2,4-D. © 1990, Gustav Fischer Verlag, Stuttgart. All rights reserved.