Figure 4. Changes in enzyme activities measured at four positions down the stem in two high (¡) and two low (l) commercial cane sugar (CCS) clones selected from the IJ76-514 x Q165 introgression population. Each point is the mean ± SE of six measurements. Activity of sucrose synthase forward (a) is expressed as µg sucrose produced mg protein^–1 min^–1 whereas sucrose synthase reverse (b) is expressed as sucrose cleaved mg protein^–1 min^–1. Cell wall invertase activity (c) is expressed as ng sucrose cleaved g FW^–1 min^–1.