Application of boron with calcium affects respiration and ATP/ADP ratio in ‘Conference’ pears during controlled atmosphere storage

SummaryInternal flesh browning and cavities frequently occur in ‘Conference’ pears during controlled atmosphere (CA)-storage, particularly under high CO2 or low O2 partial pressures, or both. Boron (B) appears to alleviate the occurrence of browning injuries. In three consecutive years, the effects of pre-harvest B application, alone or combined with calcium (Ca), were assessed on several physiological parameters of pear fruit stored under high CO2 conditions.‘Conference’ pear trees were sprayed with B up to six-times before harvest, with or without additional Ca and, after harvest, fruits were stored at –0.5°C, 5 kPa CO2 + 2 kPa O2. During the subsequent 5-month storage period, pears were removed from storage and monitored for fruit quality, physiological disorders, respiration, and the ATP/ADP status of fruit tissue. The results showed that, after CA-storage, untreated control fruits were more susceptible to internal browning than those treated with B. The lowest incidence of browning disorders was obtained in fruits sprayed with B and Ca. At harvest, fruits treated with B were also greener, firmer and less acidic than control fruits. B-treated fruits evolved less CO2 and had lower O2 uptake rates at harvest and during the 5-month storage period. The energy status, expressed as the ATP:ADP ratio, was also higher in fruits treated six-times with B. This higher ratio may have been caused by a lower demand for energy, thus allowing a greater net accumulation of ATP for maintenance of cell integrity and function.