Ferricyanide-Mediated Transport of Chloride by Anaerobic Corn Roots

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Abstract
Chloride uptake under anaerobic conditions by 2-day corn roots was stimulated by sodium ferricyanide. The stimulation could be resolved into 2 components, 1 due to the Na ion and 1 to the ferricyanide. Na-induced transport was not reduced in the presence of a variety of metabolic inhibitors and was only weakly depressed by bromide ions, and is concluded to represent passive uptake due to a change in the membrane potential of the root cells. Ferricyanide-induced transport of chloride depended upon glycolysis and the tri-carboxylic acid cycle, and was abolished by agents which uncouple electron transfer from phosphorylation. It was reduced by bromide ions to the same extent as aerobic chloride uptake. Activity of the tricarboxylic acid cycle and oxidative phosphorylation appeared to be initiated under anaerobic conditions by ferricyanide reduction in the respiratory chain, and the reduction could be demonstrated in isolated corn-root mitochondria. Both ferricyanide reduction and ferricyanide-induced transport were inhibited by amytal but not by antimycin A, indicating that ferricyanide interacted with the respiratory chain at a locus proximal to cytochrome-c. Electron transfer over an abbreviated portion of the respiratory chain thus supports a metabolic transport of salt. The results indicate that oxidative phosphorylation during electron transfer is the crucial process in salt transport.