Effects of various CA-storage conditions on ATP, ADP and pyridine nucleotide levels related to the incidence of physiological disorders in 'Conference' pears

The effects of four controlled atmosphere (CA) storage conditions on ATP and ADP levels, and on the concentrations of NAD(H) and NADP(H) were investigated in relation to the incidence of physiological disorders in 'Conference' pears during 6 months at 0 degreesC (+/-0.5 degreesC). ATP concentrations of fruits stored in CA were substantially reduced, possibly because of a diminished respiration rate. ATP levels were less reduced in fruits kept in 1.5% CO2 + 1.5% O-2 than in those under the other CA combinations. Pears under 6% CO2 + 0.5% O-2 exhibited a strong decrease in ATP levels, with a fivefold reduction in the ATP:ADP ratio during storage, indicating an accentuated decline in tissue energy charge. In some treatments ADP showed opposite behavior to ATP: ADP accumulated under ULO storage, but in air or under moderated CA conditions, its concentration decreased. The concentrations of NADH and NADPH increased and those of oxidized NAD and NADP decreased during storage, but there were no significant differences between CA-and air-stored fruits. 'Conference' pears exhibited disorders such as flesh browning, brown heart and cavities under all CA-storage conditions, and the severity of these injuries depended on the gas combination and storage duration. The CA containing 1.5% CO2 + 1.5% O-2 seemed to be most promising since it resulted in a very low percentage of damaged fruits. Whereas the pyridine nucleotide concentrations showed no relationship to the injuries, the reduction in the ATP levels did appear to be related to the development of the damage.