Effects of Carbon Dioxide on Activity of Apple Mitochondria

Effects of CO(2) on mitochondrial activity of apple (Malus pumila Mill. var. Richared Delicious) were studied in two ways. Immediate effects were determined by imposing 3 to 18% CO(2)-bicarbonate mixtures on isolated apple mitochondria, and long term effects were determined by extracting mitochondria from apples that had been stored for intervals in atmospheres containing 6 or 12% CO(2) plus 3% O(2). The CO(2)-bicarbonate systems had immediate and broad effects on mitochondrial oxidations: 18% CO(2) stimulated malate oxidation about 10%; suppressed alpha-ketoglutarate, citrate, and NADH oxidations about 10%; and suppressed fumarate, pyruvate, and succinate oxidations about 32%. The effects of lower CO(2) concentrations varied with substrates. Mitochondria isolated from fruit stored in 6 or 12% CO(2) possessed a reduced capacity to oxidize added succinate or NADH, but retained a marked sensitivity to CO(2)-bicarbonate mixtures. Respiratory control in these mitochondria was somewhat reduced, but CO(2) had not acted as a strong uncoupling agent.