Effect of modified and controlled atmosphere storage on enzyme activity and senescence of Dendrobium orchids

This research investigated the effect of different atmosphere storage conditions on 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase enzyme activity; and senescence of cut Dendrobium orchid flowers. The atmosphere storage conditions under study were normal atmosphere, modified atmosphere packaging, and controlled atmosphere. Under the normal atmosphere, carbon dioxide (CO(2)) and oxygen (O(2)) concentrations were 0.03 and 21 %, respectively. For the modified atmosphere packaging, cut orchid flowers were wrapped in polypropylene film prior to filling with 5 % CO(2) and 2 % O(2), while under the controlled atmosphere, CO(2) and O(2) concentrations were maintained at 5 and 2 %, respectively. The storage temperature and relative humidity were 13 °C and 95 %, respectively. The ACC synthase and ACC oxidase activity and ethylene-induced electrolyte leakage were determined and results compared. The controlled atmosphere substantially lowered ACC synthase and ACC oxidase activity and was effective in delaying senescence of cut orchid flowers, as indicated by the longest storage life of 28.33 days, followed by the modified atmosphere packaging (18.15 days) and normal atmosphere (11.67 days). The longer storage life enables suppliers of orchid flowers to efficiently manage the demand and supply and also provides exporters with new opportunities to expand into distant overseas markets. The novelty of this research lies in the use of different storage environments to investigate the senescence mechanisms at tissue level of Dendrobium orchid flowers in response to ACC synthase and ACC oxidase enzyme activity.