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 , 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.

Cut hydrangea (Hydrangea spp.) flowers are marketed at two different harvest stages, the fresh-and antiquestages. Flowers cut at the fresh-stage are harvested just after the coloring of decorative sepals is completed before flowering, and flowers cut at the antique-stage are harvested when the decorative sepals develop green and/or red colors after flowering. In almost all cultivars, an increase in the hydraulic conductance of the stomata (stomatal conductance) of the abaxial side of decorative sepals occurs during the transition from the fresh to the antique-stage. We investigated the relation between the stomatal conductance increase and the severity of the damage to decorative sepals. The degree of stomatal conductance increase regressed with the severity of the damage occurrence to the antique-stage decorative sepals before harvest. The relation between the stomatal conductance increase and vase life of antique-stage cut hydrangea flowers was also investigated. Abscisic acid (ABA)-treated antique-stage cut flowers exhibited lower stomatal conductance on the abaxial side of decorative sepals than control cut flowers. A photoperiodic change in the transpiration was observed in the control cut flowers, but not in ABA-treated cut flowers. These ABA treated cut flowers had longer vase lives than control cut flowers. To achieve minimal damage before harvest and longer vase life in the antiquestage during cut hydrangea flower production, screening for stomatal conductance non-increasing cultivars would be desirable. Since the stomatal conductance of antique-stage decorative sepals showed a highly significant correlation with fresh-stage decorative sepals, these can be used as an index in screening for stomatal conductance non-increasing cultivars.

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