Effects of Bacterial Proliferation and Soluble Carbohydrate Levels on the Vase Life of Cut Dahlia (Dahlia variabilis) Flowers

Cut dahlia (Dahlia variabilis) flowers have recently become popular in Japan, but have the disadvantage of only having a short vase life. Here, we sought to clarify which factors are responsible for this by investigating the effects of an antibacterial (CMIT/MIT) treatment and a combined glucose plus antibacterial (Glc + CMIT/MIT) treatment on the vase life of the cut flowers of 10 dahlia cultivars, as well as the bacterial growth kinetics in their vase solutions and the soluble carbohydrate contents of their petals. We found that the CMIT/MIT treatment extended the vase life of `Kamakura', 'Magic Pink' and 'Purple Stone', all of which had relatively high numbers of bacteria in their vase solutions. By contrast, the Glc + CMIT/MIT treatment significantly extended the vase life of three cultivars and also increased the fresh weight of nine cultivars. A comparison of two cultivars with relatively long and short vase lives ('Moon Waltz' and 'Port Light Pair Beauty', respectively) showed that a longer vase life was related to a higher carbohydrate content in the petals. Together, these findings suggest that maintaining the carbohydrate level is important for extending the vase life of cut dahlia flowers.