Inhibition of transpiration from the inflorescence extends the vase life of cut hydrangea flowers

The relationship between transpiration from the inflorescence and the vase life of cut hydrangea ‘Endless Summer’ flowers was studied. In the defoliated cut flowers, the vase life increased with a decreasing number of decorative florets. Cut flowers having small inflorescences with 189 decorative florets exhibited a lower level of transpiration (7 g·day^-1) and longer vase life (15 days) than those having large inflorescences with 422 decorative florets. The stomatal conductivity of the decorative sepals was very low, ranging from 2.7 mmol·m^-2·s^-1 to 3.3 mmol·m^-2·s^-1, and approximately 6% of the stomata were observed to be open microscopically. In addition, diurnal change of transpiration from a defoliated cut flower was not observed. These observations indicate that most of the transpiration from the sepals is through cuticular transpiration. The use of defoliated cut flowers that do not bear too many decorative florets and treatments that suppress transpiration from the surface of the decorative sepals would be effective for the vase life extension of cut hydrangea flowers.