Sucrose Catabolism in Developing Roots of Three Beta vulgaris Genotypes with Different Yield and Sucrose Accumulating Capacities

The functions of individual sucrolytic enzymes in sugar­ beet (Beta vulgaris) roots are poorly understood, although a positive association between sucrose synthase activity and root size, and a negative association between soluble acid invertase activity and sucrose concentration have been documented. To test the veracity of these relationships and determine whether any sucrolytic activities were associated with root yield or sucrose accumulation, sucrolytic enzyme activities, fresh and dry mass, and the content of sucrose, glucose, fructose and cell wall materials were measured in roots of three B. vulgaris genotypes with differing yield and sucrose accumulating capacities at five stages in their development. Across all genotypes and developmental stages, sucrose synthase activity was positively associated with root mass, water content, and accumulation of cell wall materials. No meaningful association was observed between alkaline invertase, soluble acid invertase or insol­ uble acid invertase activities and any of the physical or chemical properties examined. These results suggest that sucrose synthase activity may be a marker for root yield, a factor in root sink strength, and a promoter of cell wall biosynthesis.