Osmotic regulation via carbohydrate metabolism drives petal expansion and floret opening in gentian ‘Showtime Spotlight’

•Accumulation and hydrolysis of gentianose and gentiobiose were stage-specific.•Changes in carbohydrates were paralleled by changes in glycoside hydrolase activity.•Changes in carbohydrates imply an important role in controlling floret development.•Carbohydrate metabolism influences development via osmotically driven cell expansion.