Acid invertase activities of dahlia ‘Kokucho’ petals during flower opening and following cutting and treatment with 6-benzylaminopurine

Abstract

Extending the vase life of cut dahlia ‘Kokucho’ flowers through enhanced activities of acid invertases (cell wall, CWIN and vacuolar, VIN) on flower opening and senescence after harvest was investigated. The activities of CWIN and VIN were very low in the outer petals at the tight bud stage (stage 1), increased markedly at the half-open stage (stage 2), and decreased at the fully open stage (stage 3) to levels lower than at stage 2. Glucose and fructose concentrations were very low at stage 1, markedly increased at stage 2, and further increased at stage 3. These results suggest that acid invertase activities play a very important role in increasing soluble sugars of petals during flower opening. Following harvest at stage 3, florets or cut flowers were treated with 50 μmol L−1 6-benzylaminopurine (BA) by dipping or spraying, respectively. These treatments extended vase life longer than in the controls. In the florets experiment, CWIN and VIN activities were significantly higher with a BA dip than in the control for petals at 3 and 6 d, but there were no significant differences in sugar concentrations between the control and BA dip groups. In cut flowers at 3 d after cutting, VIN activity and glucose concentration were higher in the outer petals treated with BA spray than in control petals. From these results, application of exogenous cytokinin has some effect of maintaining high acid invertase activity, and high invertase activity itself may be important for delaying senescence in cut dahlia flowers. BA application is useful for extending petal longevity and is expected to be a popular post-harvest treatment in cut dahlia flowers.