Role of carbohydrates in flower bud opening in rose (Rosa hybrida L.)

To explore the relationship between carbohydrate metabolism and flower bud opening in roses, experiments were conducted betweeen 2003 - 2005 on two cultivars of cut-rose (Rosa hybrida L.),'Grandgala' and 'First Red'. Flower stems were harvested at different developmental stages. Petals were separated from seven different petal whorls in flowers (outermost-to-innermost) of 'Grandgala' and 'First Red' at six developmental stages [S1, S2 and S3 represented attached blooms, and S4, S5 and S6 were detached (vase) blooms]. A substantial increase in starch accumulation was observed during the first three stages (S1 - S3) of flower bud development, while a pattern of starch degradation was observed in the later developmental stages. Differential patterns of sugar accumulation were noted in the expanding petals of rose. Levels of non-reducing sugars and sucrose increased gradually with flower bud development up to stage S3 of flower bud opening. In contrast, levels of reducing sugars increased continuously during all six stages of flower bud development. The total sugar content of flower petals followed a similar pattern to that observed for reducing sugars. A close relationship was observed between sucrose accumulation and the activity of sucrose phosphate synthase (SPS). This is the first report of high SPS activity in rose petals, and provides preliminary evidence for differential enzyme activity during flower bud opening. Collectively, these data support the hypothesis that carbohydrates play an important role in flower bud opening in rose.