Abstract
Oxygen reduction by mitochondria prepared from young bean root tips is inhibited by the herbicide ioxynil. This inhibition can be reversed by menadione (vitamin K3) and by ubiquinol but not by ubiquinone. Ioxynil is thought to inhibit ubiquinone reduction when succinate or NADH is supplied as substrate to isolated mitochondria. The addition of bovine serum albumin to mitochondrial preparations appears to reduce the inhibitory effects of ioxynil.