Metabolic scheme. The principal pathways considered in this study. The stars indicate the reactions consuming ATP or UTP and the flux names are indicated. Vg, Glc uptake; Vhk, hexokinase activity; Vgpase, Glc-6-phosphatase activity; Vsta, starch synthesis; Vats, starch degradation; VSuSy, Suc synthase activity; Vsps, Suc phosphate synthase activity; Vi, invertase activity; Vwall, cell wall polysaccharide synthesis; Vwalld, cell wall polysaccharide degradation.