Effects of 2,4-D and Other Herbicides on Oxidative Phosphorylation in Mitochondria from Cabbage

The effects of 22 herbicides on oxidative phosphorylation in mitochondria from cabbage ( Brassica oleracea var. capitata L.) have been studied. Carbamates, phenoxyacids, 3,5-dimethyltetrahydro-l,3,5,2 H -thiadiazine-2-thione (DMTT), N -1-napthylphthalamic acid (NPA), 2,3,6-trichlorobenzoic acid (2,3,6-TBA), 3-( p -chlorophenyl)-1,1-dimethylurea (monuron), and 2-chloro-2- N,N -diallylacetamide (CDAA) inhibited phosphorylation to a greater extent than oxygen uptake in cabbage mitochondria. The compounds 1,2-dihydropyridazine-3,6-dione (MH), 2,2-dichloropropionic acid (dalapon), 2,2,3-trichloropropionic acid (hereinafter referred to as 2,2,3-TPA), sodium chlorate, and 3-amino-l,2,4-triazole (amitrole) at concentrations as high as 1 × 10 –2 M did not have a large effect on oxidative phosphorylation in cabbage mitochondria. Respiration which was stimulated by 2,4-dinitrophenol (DNP) or adenosine diphosphate (ADP) was inhibited by 2,4-dichlorophenoxyacetic acid (2,4-D). Although 2,4-D did not affect Mg ++ -stimulated adenosine triphosphatase (ATPase), it inhibited an oleate-stimulated ATPase activity and the ATP- 32 Pi exchange reaction in cabbage mitochondria. The results suggest that 2,4-D may inhibit respiration in cabbage mitochondria by an effect on a reaction involved in coupling phosphorylation with electron transport.