Effects of Carbon Dioxide on Activity of Apple Mitochondria

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Effects of CO2 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% CO2-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% CO2 plus 3% O2. The CO2-bicarbonate systems had immediate and broad effects on mitochondrial oxidations: 18% CO2 stimulated malate oxidation about 10%; suppressed α-ketoglutarate, citrate, and NADH oxidations about 10%; and suppressed fumarate, pyruvate, and succinate oxidations about 32%. The effects of lower CO2 concentrations varied with substrates. Mitochondria isolated from fruit stored in 6 or 12% CO2 possessed a reduced capacity to oxidize added succinate or NADH, but retained a marked sensitivity to CO2-bicarbonate mixtures. Respiratory control in these mitochondria was somewhat reduced, but CO2 had not acted as a strong uncoupling agent.

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