Mechanism of Sugar Storage by Mature Stem Tissue of Sugarcane

Sugar uptake by sugarcane cells in suspension culture was measured over short incubation time spans (5 seconds to 4 minutes), and membrane transport rates were calculated. A relatively high proportion of labeled products in cell extracts after incubation of cells with "4C-glucose for 5 seconds was sugar phosphates (56%); fructose and sucrose began to appear after 15 and 30 seconds, respectively. Galactose and 3-0-methylglucose competed appreciably with glucose uptake, but ketohexoses and pentoses did not; there was no detectable uptake of sucrose. It is postulated that besides endogenous phosphorylation and further metabolism of glucose the configuration of the hydroxyl on the carbon-2 may be important for efficient membrane transport. The cells had a particularly high affinity for glucose and 3-0-methylglucose (Km = 15 and 16^M , respectively).

mentioning

confidence: 70%

Membrane Transport of Sugars in Cell Suspensions of Sugarcane

Maretzki

Thom

1972

“…5) support that suggestion. Sucrose inversion has been shown to be a prerequisite to sugar uptake by some tissues (6,12) and in part II of this series (16) we report that invertase activity is very high in both the pedicel and the placento-chalazal tissues. The placento-chalazal tissue is located between the pedicel and the specialized cells of the basal endosperm (8).…”

Section: Discussionmentioning

confidence: 92%

Movement of ¹⁴C-Labeled Assimilates into Kernels of Zea mays L

Shannon

1972

Carbon-14, photosynthetically fixed in leaves of Zea mays L. and translocated to developing kernels, passed through specialized basal endosperm cells prior to movement into the starchy endosperm and embryo. Radioactivity migrated in the endosperm at a maximum rate of 2.7 millimeters per hour, and there was no difference in the rate of movement in kernels treated 14 to 30 days after pollination.Sucrose contained over three-fourths of the radioactivity in the kernal base (fruit stalk) 1 to 6 hours after "CO2 treatment of the plant. Conversely, in the basal endosperm three-fourths of the radioactivity was in glucose and fructose. A high proportion of the radioactivity was retained in the monosaccharides of the starchy endosperm the first 3 hours after the "CO2 except where noted, were exposed to 250 to 400 ,uc of "CO2 for 30 mim as described previously (14). The ear leaves of the plants studied 16 and 18 days after pollination were damaged at the time of pollination, therefore the first leaf above the ear was exposed to "CO2 as above. The ears, when enclosed within the treatment bag, were covered with aluminum foil to inhibit any fixation of "CO2 by the ear husks. One-sixth of each ear was collected at various times after beginning the treatment as described previously (14). The ear pieces were rapidly frozen by either dropping them into liquid nitrogen or Dry Ice. The samples were then freezedried. In order to reduce collapse of the kernels during drying, cuts were made through the pericarp at the top or sides of the kernels prior to freezing.Preparation of Kernel Sections for Radioautography. Six freeze-dried kernels from a plant treated 21 days after pollination were carefully removed from the cob and placed in 60 C paraffin (Paraplast,3 Scientific Products, Evanston, Ill.). The kernels were vacuum infiltrated for 15 hr at 60 C after which time the original paraffin was replaced with fresh paraffin. Vacuum infiltration was continued for 6 hr prior to embedding in fresh paraffin. The blocks containing the kernels were warmed to 37 C and sliced into sections approximately 0.8 mm thick. Freehand sections were cut with a razor blade using a slicing guide. The embedded sections were arranged on mount paper and placed briefly on a warm plate to melt enough paraffin to fix the sections to the paper. To determine the rate of "C movement in the kernels, 16 freeze-dried kernels from each sampling time were cut in half along the central axis perpendicular to the face of the kernels. One-half of each kernel was mounted with rubber cement to a sheet of foam plastic. Kodak No-Screen or Kodak Royal Blue x-ray film was placed over the mounts and left for 1 week exposure prior to development by standard procedures. Portions of the x-ray film adjacent to the radioactive areas of the kernel pieces were darkened. By carefully comparing the radioautograph ' Mention of a trademark name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the United States Department of Agriculture and ...

“…The resulting hexoses are actively accumulated into the storage parenchyma and resynthesized to sucrose phosphate by sucrose phosphate synthetase. Sucrose transport into the storage vacuole is presumably mediated by a specific sucrose phosphate phosphatase (7). In the mature cane stalk, alkaline invertase has been proposed to regulate sucrose storage and utilization.…”

mentioning

confidence: 99%

Sucrose Translocation and Storage in the Sugar Beet

Giaquinta

1979

116

Several physiological processes were studied during sugar beet root development to determine the celular events that are temporally correlated with sucrose storage. The prestorage stage was characterized by a marked increase in root fresh weight and a low sucrose to glucose ratio. In spite of the agronomic importance of translocation, the cellular processes associated with the partitioning of translocate to the harvestable portions of crops represent one of the most poorly understood areas in translocation. In terms of import region physiology, the mechanism of sucrose storage in sugarcane stalks has perhaps received the most investigation (5-7). The conclusion reached from these studies was that sucrose translocated to the stalk enters the free space where it is hydrolyzed by a cell wall acid invertase (6). The resulting hexoses are actively accumulated into the storage parenchyma and resynthesized to sucrose phosphate by sucrose phosphate synthetase. Sucrose transport into the storage vacuole is presumably mediated by a specific sucrose phosphate phosphatase (7). In the mature cane stalk, alkaline invertase has been proposed to regulate sucrose storage and utilization. In contrast, immature cane contains an intracellular acid invertase in addition to a cell wall acid invertase. During cane development the intracellular acid invertase activity disappears with a concomitant increase in alkaline invertase activity (5).The