sucrose, cane sugar, the most common of the sugars, is ubiquitous in plants because it is the preferred compound for phloem translocation of energy and carbon around the plant. Sucrose consists of a glucose molecule joined to a fructose molecule. Breakdown (hydrolysis) of sucrose is achieved readily by the enzyme invertase, which ‘inverts’ it to these hexoses.
Invertase in the vine occurs in cell wall spaces but not in those of the leaf, which is why sucrose is confined in vines mainly to leaves and phloem tubes. Invertase is abundant in grape berries both in the cell walls and in the vacuoles; hence the sugars that accumulate in berries are mainly glucose and fructose.
