Accumulation and Transformation of Sugars in Sugar Cane Stalks

Sugar Accumulation Cycle in Sugar Cane. III. Physical & Metabolic Aspects of Cycle in Immature Storage Tissues

“…We suggest the role for the invertase in the storage compartment is concerned with the rate of return of sugar froml storage which will be a function of the concentration of the enzime if the vacuolar membrane is more permeable to hexoses than to sucrose. The feasibility of this proposition has been dlemonstrated by the construction of artificial membranes having such properties (5); also direct evidence was provide(l by the leakage studies reported earlier (6). Apparently a regulatory system for controlling the enzyme level is coupled to the amount of hexose present in the metabolic compartment since when glucose or fructose are supplied to tissue slices there is a rapid decline in the content of the inner space invertase (15).…”

“…A second feature which Canna leaf discs and immature cane storage tissues have in common is an outer space invertase. However, a major difference is apparent in the origin of the endogenous hexose pools which, in cane, have been shown to arise from sucrose accumulated into the storage compartment (6,7, & this paper). For Canna leaf, no movement of label from accumulated sucrose into the endogenous hexoses was detected.…”

“…Reducing sugars in the storage compartnment are derived froml hydrolysis ot accumulated sucrose (7). All sugars diffuse slowly from the storage compartment, reducing sugars diffusing more rapidly than sucrose (6). Immature storage tissue contains an invertase which is optimally active between pH 5.0 -and 5.5 (8,11).…”

“…Among these was their demonstration that ra(lioactive carbon, fixed photosynthetically from CO., supplied to a single leaf, moves to all stalks in a stool of cane (4). Our work on intact cane stalks has shown that sugar may be returnedl from storage for local utilization (6) or nlay be translocated and used elsewhere (10 …”

The Regulation of Invertase Synthesis in Sugar-Cane: Effects of Sugars, Sugar Derivatives, and Polyhydric Alcohols

“…If a sugar and not a derived metabolite is the natural suppressor for invertase synthesis, we probably need only consider glucose, fructose, and sucrose. Since they are readily interconverted in the tissue (Glasziou 1960), the observation that each of these sugars suppresses invertase synthesis when supplied in the medium bathing tissue slices (Sacher and Glasziou 1962) The effect of n~glucose on invertase synthesis in tissue slices is closely simulated by 2~amino~n~glucose, these two sugars giving equivalent effects over a 20~fold concentration r.ange and also at three different pH values. Metabolism of 2 amino·n· glucose yields 2.amino·n.glucose phosphate and an unidentified substance and its phosphorylated derivative.…”