Activation of endogenous respiration and anion transport in corn mitochondria by acidification of the medium.

Acidification of the suspending medium of corn mitochondria (Zea mays L., WF9 x Mo17) from pH 7.5 to pH 6.8 to 6.4 initiates osmotic swelling with the transportable anions citrate, sulfate, and phosphate. Swelling becomes pronounced with a combination of citrate plus sulfate or phosphate. Acidification proves to activate endogenous respiration, which is essentially zero at pH 7.5. The endogenous respiration transports citrate (in the presence of sulfate or phosphate) which then contributes to respiration and the accelerated osmotic swelling. Mersalyl will inhibit the swelling and antimycin inhibits the endogenous respiration. Magnesium appears to reduce the permeability of the membranes under the acid conditions.