Action of the herbicides neburon and siduron on membrane permeabilities in potato tuber mitochondria

The herbicides neburon and siduron are uncouplers of oxidative phosphorylation in potato tuber (Solanum tuberosum L. cv. Bintje) mitochondria. Their effect on the ion permeabilities of the mitochondrial membrane was investigated using the acid-base pulse technique, swelling experiments and integrity tests. Both herbicides permeabilize the membrane to H⁺ ions. They have no action on the permeabilities of K⁺ and Fe(CN)^3?₆. The swelling observed with Ca²⁺ was better interpreted as an effect on membrane structure than as a true swelling. Diuron, a parent compound that does not uncouple oxidative phosphorylation, does not act on Ca²⁺-induced apparent swelling.