Effects of temperature on gas exchange of 'Braeburn' apples

Gas exchange attributes of fruits affect their responses to modified atmosp here and surface coating treatments. In this study, variations in respirati on rate, internal partial pressures of O-2 and CO2, and skin permeance to O -2 and CO2 associated with storage at 0, 5, 10, 15, 20, 25, and 30 degrees C were characterised in 'Braeburn' apples (Malus domestica Borkh.) There wa s an 11-fold difference in respiration rate between fruit kept at 0 and 30 degrees C, although permeance to each of the two respiratory gases differed only by a factor of two. The differing effects of temperature upon these t wo variables was responsible for the depression of internal O-2 and elevati on of internal CO2 associated with increase in temperature from 0 to 30 deg rees C. The magnitude of decline in internal O-2 was slightly greater than the increase in internal CO2 over the temperature range in the experiment. For apples that were respiring aerobically, and with a respiratory quotient of unity, this would indicate that the fruit skin had a somewhat higher pe rmeance to CO2 than to O-2. Permeance Values for the two respiratory gases were strongly related but permeance to CO2 exceeded that to O-2 for fruit w ith a low permeance to O-2. This is attributable to the greater ease of dif fusion of CO2 through the cuticle, an effect which became more pronounced a s transcuticular diffusion was facilitated at high temperatures. Given the importance of internal atmosphere composition in affecting respiration rate and disorder development in apples, the gas exchange characteristics of 'B raeburn' appear likely to be influential in the outcome of different storag e regimes.