Vol. 71 No: 6

Title:
Respiratory Characteristics and Calculated ATP Production of Apple Fruit in Relation to Tolerance of Low O₂ Concentrations

Authors:
H.W. PEPPELENBOS and R. RABBINGE

pp: 985-994

Abstract:
The applicability of respiratory characteristics to determine optimal O₂ concentrations for the storage of apples was tested. A comparison was made between gas exchange rates of apples directly after harvest and after a period of storage. Apples of three harvest dates were used. Optimal O₂ concentrations were based on gas exchange data and gas exchange models fitted on the data, using the Anaerobic Compensation Point (ACP) and the Respiratory Quotient Breakpoint (RQB). A third way was comparing total ATP production with estimated maintenance energy requirements, revealing the Maintenance Oxygen Concentration (MOC). ATP production was calculated using gas exchange models. MOC was defined as the oxygen concentration with the minimal ATP production rate necessary for maintaining cell viability. The optimal O₂ concentrations as established by ACP, RQB and MOC differed considerably. Because ACP values differed from normally advised values, the ACP was unsuitable for a quick determination of the optimal O₂ concentration of the apples used. The RQB, however, might be suitable, but than the limit used to establish the RQB should be more than 0.5 units higher than the RQ measured in normal air. The ACP and the RQB were decreased to lower O₂ concentrations after storage, suggesting that optimal concentrations decreased during storage. In contrast the MOC was increased after storage, in agreement with results found in practice. Model calculations indicated the lowest optimal O₂ concentration for the second (optimal) harvest using the ACP, the RQB and the MOC. It is suggested that research on the relationship between Maintenance Energy Requirements (MER) and cell injury will clarify an important part of the changes in optimal O₂ concentrations (or the tolerance to low O₂ concentrations) during ageing or maturation or harvested plant tissues.

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