The Water Balance of Cut Rose Flowers

A sharp decline in water potential of petal tissue associated with wilting of cut rose flowers is described. Such a decline did not develop in senescing intact flowers. A circadian rhythm in water absorption by cut flowers was observed. The decline in fresh weight observed in the last phase of the vase life of cut flowers occurred earlier in a short‐lived cultivar than in a longer‐lived one. A decline in potential conductivity to water was observed with time in stems of cut roses. Concomitantly cellulase activity increased after cutting. Flowers held in cellulase solution wilted earlier than the controls. However, no difference was found in these two parameters between two cultivars differing in their longevity. The difference in longevity between the two cultivars was large especially under conditions promoting high transpiration rates, and was narrowed when flowers were either held in mild conditions, or the leaves were stripped off. Although stomates were equally open in intact flowers of the two cultivars, in cut flower shoots of the short‐lived cultivar stomates were more widely open. In accordance transpiration rates were higher, and wilting occurred earlier in the short‐lived cultivar than in the long‐lived one. It is concluded that the earlier wilting of cut flowers of the short‐lived cultivar is mainly due to lower ability to close stomates in response to water stress conditions, and not to earlier formation of vascular blockage.