Changes in Concentrations of Sugars and Organic Acids in the Long-Lasting Flower Clusters of Phalaenopsis

The explanation for the maintenance of the quality of flowerclusters in Phalaenopsis for up to four weeks or more was determined.The concentration of sugars and organic acids and the dailycourse of CO₂ exchange in the florets, the flower stalk andthe leaves of intact and cut flower clusters were determined.The concentration of sugars in florets of the cut flower clustersdecreased progressively and linearly to 25% of the initial value.The concentration of organic acids in the flower stalk of theintact flower cluster increased progressivly, whereas the concentrationof malic acid in the flower stalk of the cut cluster decreased.The levels of sugars and organic acids in leaves in the absenceof a flower cluster was higher than those in leaves in the pressenceof a cluster. The leaves and the flower cluster were relatedas source and sink organ, respectively. The level of sugarsin the flower cluster remained high level for a long periodof time. The results indicate that the stalk'is capable of photosynthesisand has the characteristics of weak-CAM plants. The photosynthateproduced by the stalk served to maintain the quality of thecut flower cluster for at least for 50 days and that of theintact flower cluster. (Received August 22, 1991; Accepted September 30, 1991)