Sucrose Storage Research Articles

Sugar transport and sugar-metabolizing enzymes in sugar beet storage roots ( Beta vulgaris ssp. altissima)

Sugar uptake studies with isolated protoplasts from sugar beet roots indicated that glucose is transported preferentially, obviously by a H + /glucose symport mechanism. The uptake rate in conducting tissue exceeded that of storage tissue. Fructose and sucrose seemed to be transported by lower affinity. The apparent KM for fructose and sucrose was 7.8 and 18.6 mM respectively, whereas glucose uptake had a Michaelis constant of 1.4 mM. Competition experiments led to the assumption of two different carrier systems for glucose and fructose. While comparing activities of sucrose synthase (SS, E.C. 2.4.1.13), sucrose phosphate synthase (SPS, E.C. 2.4.1.14) and acid invertase (IV, E.C. 3.2.1.26) in different parts of sugar beet roots, in protoplasts and vacuoles, we obtained information on the localization and thus the possible physiological significance of these sucrose metabolizing enzymes: conducting tissue exhibits higher activities of SS, SPS and cell-wall bound acid IV than storage tissue. However, the activity of soluble acid IV was slightly higher in the latter. Concerning the subcellular compartmentation, SS seems to be restricted to the cytoplasm whereas more than 50 % of the total SPS activity is found in the vacuolar fraction. A working hypothesis for the unloading and storage of sucrose in sugar beets is proposed.

Characteristics of plant species which store different types of reserve carbohydrates

summaryThe occurrence of the three principal reserve carbohydrates, starch, fructan and sucrose, is documented in 20 native British species over four seasons. Species containing two of the reserve carbohydrates in different combinations were present in each of three common habitats.Sucrose reserves Undergo considerable depletion after winter. Starch depletion also occurs in many though not all species. In contrast, fructan is stored in high concentrations which are not subject to depletion. This indicates the fructan has functions other than as a source of consumable carbohydrate, one of which may be as an osmotic regulator.Fructan is associated with relatively restricted phenologies associated with early‐season, low‐temperature growth. In contrast, the Storage of starch or sucrose as a principal reserve carbohydrate is associated with the broadest variation in phenological patterns. There is, however, no indication that fructan has a unique or specific‐role in low temperature tolerance as similar attributes are shown to be present in a number of non‐fructan species.In relation to herbivore nutrition, each type of carbohydrate is made relatively unavailable either in space (starch and fructan) or in time (sucrose). The consequences of these various characteristics are considered in relation to plant evolution and Survival.

Sugar Accumulation in L19 Type Sugarbeet Germplasm

Seasonal sucrose accumulation of Beta vulgaris «L19», a high sugar type inbred, was compared to that of yield type inbreds and other high sugar type inbreds and hybrids in field experiments during three years. The consistent seasonal sucrose accumulation pattern of L19 might lead to beter understanding of basic mechanisms controlling sucrose transport and storage in sugarbeet

Effects of Shading Densities on Root Chemical Composition of Sugarbeet

AbstractThe effect of different shading densities on some chemical composition of the roots of two sugarbeet cultivars was studied out during 1984/1985 season. Plants were grown under 0, 37, 50 and 70 % shading treatments.Results showed that the capacity of root tissue in production or storage of sucrose was not directly dependent on light intensity as all the shading treatments did not change the sugar percentage. Therefore, it was suggested that the sucrose percentage in the root was a genetically‐dependent character more than an environmental one.Also, shading had no significant effects on the chemical composition (protein, fiber, fat, ash and dry matter) of fresh roots at maturity, except the fiber percentage which was significantly increased only under the 70 % shading treatment.

Analysis of the Reaction Products from Incubation of Sugarcane Vacuoles with Uridine-Diphosphate-Glucose: No Evidence for the Group Translocator

Isolated sugarcane (Saccharum spp. hybrid H50-7209) vacuoles incorporate radioactivity during incubation with labeled UDP-glucose by a mechanism which was postulated to be responsible for sucrose storage in the vacuoles (UDP-glucose group translocator). Analysis of the reaction products in the medium revealed that several enzymic processes are going on during incubation with UDP-glucose such as production of hexose phosphates, UMP, and sugars, all of which seem unrelated to the incorporation of radioactivity into vacuoles. The incorporated radioactivity was identified mainly as (1-->3)-beta-glucan (callose) of polymerization grades up to more than 20. Callose occurs as a contaminant at the surface of isolated vacuoles coming from the plasmalemma. The properties of UDP-glucose incorporation into the vacuolar preparation compared favorably with known properties of callose synthase. The low mol wt glucans that are found are probably degradation products of labeled callose due to hydrolases, which are liberated by centrifugation of vacuoles. The labeled disaccharide, which chromatographically had been formerly identified as sucrose, is laminaribiose. No sucrose (or sucrose phosphate) could be identified in the vacuole preparation after incubation with UDP-glucose. Thus, the mechanism of sucrose storage in sugarcane vacuoles is still open.

Uridine 5?-diphospho-D-glucose-dependent vectorial sucrose synthesis in tonoplast vesicles of the storage hypocotyl of red beet (Beta vulgaris L. ssp. conditiva)

Tonoplast vesicles were prepared from red-beet (Beta vulgaris L. ssp. conditiva) hypocotyl tubers ("beetroot") known to store sucrose. Uptake experiments, employing uridine 5'-diphospho-[(14)C]glucose (UDP-[(14)C]glucose) showed the operation of an UDP-glucose-dependent group translocator for vectorial synthesis and accumulation of sucrose, recently described for sugarcane and red-beet vacuoles and for tonoplast vesicles prepared from sugarcane suspension cells. Characterization of the kinetic properties yielded the following results. Uptake of UDP-glucose was linear for 15 min. The apparent K m was 0.75 mM for UDP-glucose (at pH 7.2, 1 mM Mg(2+)), V max was 32 nmol·(mg protein)(-1)·min(-1). The incorporation of UDP-glucose exhibited a sigmoidal substrate-saturation curve in the absence of Mg(2+), the Hill coefficient (n H) was 1.33; Michaelis-Menten kinetics were obtained, however, in the presence of 1 mM MgCl2. For the reaction sequence under the control of the group translocator a dual pH optimum was found at pH 7.2 and 7.9, respectively. All reaction intermediates and the end product sucrose could be identified by two-dimensional high-performance thin-layer chromatography and autoradiography. The distribution pattern of radioactivity showed almost uniformly high labeling of all intermediates and sucrose. The physiological relevance of the results is discussed in the light of the fact that the tonoplast of red-beet storage cells accommodates two mechanisms of sucrose uptake (i) vectorial sucrose synthesis and (ii) direct ATP-dependent sucrose assimilation.

Sucrose Synthase and Sucrose Phosphate Synthase in Sugar Beet Plants ( Beta vulgaris L. ssp. altissima

Summary In sugar beet plants, activities of both, sucrose synthase (SS, EC 2.4.1.13) and sucrose phosphate synthase (SPS, EC 2.4.1.14), increase with plant age, in beet tissue as well as in petioles and to a lesser extent in leaves. In beets, maximum activity of SS was 33.5 μmol/mg protein · h, and of SPS 18.1 μmol/mg protein · h. Activity of SPS is significantly higher in the core than in the peripheral parts of the beet. Cell suspensions exhibited rather low activities of SPS. The data shown for beet tissue are correlated with cell growth and sucrose concentration. Somewhat in contrast with earlier reports this indicates the significance of both enzymes in the regulation of sucrose storage: SS contributes to an increase of the sink capacity, and SPS provides the steady increase of sucrose content in the growing beet.

Turgor Regulation of Sucrose Transport in Sugar Beet Taproot Tissue

Sink tissues that store osmotically active compounds must osmoregulate to prevent excessively high turgor. The ability to regulate turgor may be related to membrane transport of solutes and thus sink strength. To study this possibility, the kinetics of sugar uptake were determined in sugar beet (Beta vulgaris L.) taproot tissue discs over a range of cell turgors. Sucrose uptake followed biphasic kinetics with a high affinity saturating component below 20 millimolar and a low affinity linear component at higher concentrations. Glucose uptake exhibited only simple saturation type kinetics. The high affinity saturating component of sucrose and glucose uptake was inhibited by increasing cell turgor (decreasing external mannitol concentrations). The inhibition was evident as a decrease in V(max) but no effect on K(m). Sucrose uptake by tissue equilibrated in dilute buffer exhibited no saturating component. Ethylene glycol, a permeant osmoticum, had no effect on uptake kinetics, suggesting that the effect was due to changes in cell turgor and not due to decreased water potential per se. p-(Chloromercuri)benzene sulfonic acid (PCMBS) inhibited sucrose uptake at low but not high cell turgor. High cell turgor caused the tissue to become generally leaky to potassium, sucrose, amino acids, and reducing sugars. PCMBS had no effect on sucrose leakage, an indication that the turgor-induced leakage of sucrose was not via back flow through the carrier. The ability of the tissue to acidify the external media was turgor dependent with an optimum at 300 kilopascals. Acidification was sharply reduced at cell turgors above or below the optimum. The results suggest that the secondary transport of sucrose is reduced at high turgor as a result of inhibition of the plasma membrane ATPase. This inhibition of ATPase activity would explain the reduced V(max) and leakiness to low molecular weight solutes. Cell turgor is an important regulator of sucrose uptake in this tissue and thus may be an important determinant of sink strength in tissues that store sucrose.

Sucrose metabolism in sugar cane grown under varying climatic conditions: Synthesis and storage of sucrose in relation to the activities of sucrose synthase, sucrose-phosphate synthase and invertase

The contents of sucrose and hexoses in relation to the activities of sucrose synthase, sucrose-phosphate synthase and soluble invertase in leaf blade and of soluble and wall-bound invertase in stem tissues of sugar cane growing under naturally varying weather conditions were determined. In leaf blades, sucrose synthase, sucrose-phosphate synthase and soluble invertase were most active at tillering. Sucrose synthase was relatively more active than sucrose-phosphate synthase throughout the growth of the cane. In stem tissues the activity of soluble acid invertase was highest at the stem elongation stage and then declined, whereas the activities of soluble neutral invertase and wall-bound acid invertase increased with age. With the ageing of the cane, sucrose accumulation in the stem gradually increased with a concomitant fall in hexose content. A narrow ratio ofsucrose in the basal to top portion of the cane relates to maturity of the cane. On feeding uniformly labelled sucrose and hexoses to storage tissue for 4 hr. ca 85–90 % of the 14C in intracellular sugars was present in sucrose. Synthesis of sucrose from glucose in leaf disks was stimulated by Mg 2+ and Mn 2+.

CARBON FLUXES IN LEAF BLADES OF BARLEY

SummaryGas exchange, mass of carbohydrates, and turnover of carbohydrates, have been followed diurnally in barley leaf blades. Mature second leaf blades store sucrose, which occurs in at least two types of pool which turn over at different rates. Over a light‐dark cycle, photosynthesis, sucrose synthesis and translocation all show appreciable changes in rate but are not obviously related; nor is the rate of translocation a function of the total concentration of sucrose in the leaf. In the dark, starch mobilization starts immediately and that of sucrose increases, maintaining the mean rate of translocation in the dark at 77 % of that in the light. Fructans are turned over but show little diurnal variability in mass.

The role of the vacuole in the accumulation and mobilization of sucrose

The contribution that isolated vacuoles have made to understanding sucrose storage and mobilization is reviewed briefly, with particular reference to the storage root of red beet (Beta vulgaris L.). Work with isolated vacuoles has shown that in this tissue sucrose is confined to the vacuole and some progress has been made in elucidating the possible mechanism of sucrose transport into the vacuole. The evidence that this is a H+: sucrose antiport, dependent on the activity of a proton-translocating ATPase is examined. It is concluded that while there is some evidence for the presence of a proton pump, a link between this and sucrose uptake has still to be established. Using isolated vacuoles it has been demonstrated that during mobilization of sucrose, hydrolysis occurs within the vacuole but the mechanism of unloading of hexoses from the vacuole remains to be elucidated.

Effect of Time and Amount of Nitrogen Uptake on Sugarbeet Growth and Yield1

AbstractSugarbeet (Beta vulgaris L.) root quality has been steadily decreasing since the early 1950's with increased use of N fertilizer. Since the extent of these decreases may be associated with the time and amount of N uptake, the objective of this study was to evaluate the effects of several rates and times of N fertilizer applications and N uptake by sugarbeets on seasonal growth rates, sucrose percentage and accumulation, dry matter production, and partitioning of the photosynthate.Sugarbeets were grown under field conditions on a Portneuf silt loam soil (Durixerollic Calciorthids, coarsesilty, mixed, mesic) near Twin Falls, Idaho, in 1977, using four N rates, each applied preplant, mid‐June, mid‐July, and mid‐August. Root yields, sucrose concentration and yield, dry matter production, leaf area index, and plant N uptake were determined from samples taken throughout the season. Adding N fertilizer above that needed for optimum plant growth or delaying N application until midseason caused a greater proportion of the photosynthate to be used for increased top growth at the expense of dry matter and sucrose accumulation in the roots. Sucrose accumulation was maximum from late July until early September; therefore, during this period, addition of N and N uptake by the plant caused the greatest decrease in sucrose accumulation and production at harvest. Increasing N levels decreased sucrose concentrations during the season and at harvest because of 1) increased moisture level of roots, and 2) dry matter produced and accumulated in the roots having a decreased sucrose concentration. The rate of accumulation of stored sucrose was reduced by midseason N application, but stored sucrose was not used for increased growth of beet tops. Excess and late N applications also increased impurities in the beet root, decreasing extractability of stored sucrose, which further decreased refined sucrose production. Early application of N fertilizer at optimum levels should maximize refined sucrose production.

Sucrose Efflux from the Maize Scutellum

AbstractSucrose efflux from maize scutellum slices was promoted by high pH and by K+, Na+ or Rb+. Incubation in mannose (which drastically reduces the ATP level) caused high rates of sucrose efflux only when KCl was present at pH 8. The effects of triphenylmethylphosphonium ion (TPMP+, a lipid soluble cation) on sucrose efflux were similar to those of mannose plus KCl. Mannose and TPMP+ caused release of stored sucrose into the cytoplasm, but pH8 and KCl (mannose) or pH 8 (TPMP+) in the bathing solution were necessary for rapid efflux of sucrose. Rb+ uptake took place during sucrose efflux. In mannose, rates of Rb+ uptake and sucrose efflux were low at pH 5.6 and high at pH 8.0, although the time courses for uptake and efflux were different. It is concluded that sucrose efflux is electrogenic and that it occurs as sucrose‐H+ symport. A scheme for sucrose transport across plasmalemma and tonoplast is presented.

Comparative Enzymic Studies of Sucrose Metabolism in the Taproots and Fibrous Roots of Beta vulgaris L

Comparative enzymic studies of sugar beet (Beta vulgaris L.) taproots and fibrous roots revealed differences in invertase (EC 3.2.1.26) and sucrose synthetase (EC 2.4.1.13) activity. Invertase activity of the two root forms differs with respect to specific activity, pH optimum, and enzyme solubility. Acid invertase (pH 4.5) in the taproot was restricted to the peripheral meristematic tissue which produces cells for both taproot and fibrous root growth. This finding supports the hypothesis that the enzyme regulates sucrose partitioning between the taproot and fibrous roots. A distinct alkaline invertase (pH 8.0) was detected in sucrose storage tissues of the taproot.The V(max) of taproot sucrose synthetase (sucrose cleavage reaction) was highest in the presence of UDP. However, the fibrous root enzyme had the highest V(max) with ADP as substrate. Differential nucleoside diphosphate substrate affinities may provide for compartmentation and separate regulation of sucrose cleavage and resultant hexose utilization in adjoining taproot and fibrous root tissues.

Sucrose Translocation and Storage in the Sugar Beet

Several physiological processes were studied during sugar beet root development to determine the cellular 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. Carbon derived from (14)C-sucrose accumulation was partitioned into protein and structural carbohydrate fractions and their amino acid, organic acid, and hexose precursors. The immature root contained high soluble acid invertase activity (V(max) 20 micromoles per hour per milligram protein; K(m) 2 to 3 millimolar) which disappeared prior to sucrose storage. Sucrose storage was characterized by carbon derived from (14)C-sucrose uptake being partitioned into the sucrose fraction with little evidence of further metabolism. The onset of storage was accompanied by the appearance of sucrose synthetase activity (V(max) 12 micromoles per hour per milligram protein; K(m) 7 millimolar). Neither sucrose phosphate synthetase nor alkaline invertase activities were detected during beet development. Intact sugar beet plants (containing a 100-gram beet) exported 70% of the translocate to the beet, greater than 90% of which was retained as sucrose with little subsequent conversions.

Anatomical features of stem in relation to quality and yield factors inSaccharum clones

The results from a study of the relationships between external productive features of millable canes and quality characters as well as anatomical differences of stem in relation to both yield components and quality factors in 16 clones ofSaccharum involving rinded and rindless samples are discussed in this paper. The wide variations recorded for the various characters studied brought out the diversity in the genotypes besides indicating the relative importance of certain attributes in production and quality breeding, where cane weight and sucrose content play a leading role. The study revealed the major contribution of rind to fibre content and the value of appropriate levels of fibre as also the need for examining the different physical characteristics of the fibre which are conducive to both high levels of sucrose storage potential and better milling quality. From anatomical studies, varietal differences were recorded, but neither the smallest nor the largest cell volume was associated with extreme levels of fibre, brix or sucrose content.

A Comparison of Rates of Storage of Sucrose in Eight Clones of Sugar-cane as Measured by Sucrose Uptake in vitro

A Comparison of Rates of Storage of Sucrose in Eight Clones of Sugar-cane as Measured by Sucrose Uptake in vitro

The hyperactivity of hamster fibroblast lysosomal enzymes after endocytosis of sucrose

The uptake of intralysosomal storage of sucrose by hamster fibroblasts results in increases in the activities of several types of lysosomal enzymes. The increases are not restricted to glycosidases. The activities of plasma membrane and Golgi apparatus enzymes are also increased whereas enzymes of other organelles are not affected. Uptake of sucrose causes the cessation of endocytosis within 5 hours. The time course of increases in enzyme activities demonstrates that the initial changes occur in the plasma membrane.

Development of tuberous roots and sugar accumulation as related to invertase activity and mineral nutrition

Sucrose storage in tuberous roots was not observed when the tissues had very high activities of acid invertase. High activities of the enzyme were always present in the roots at early stages of their development. In species where the activity of the enzyme decreased during root development, sucrose was stored. Thus, acid invertase was undetectable in mature roots of carrots (Daucus carota L.) where sucrose formed almost 80% of the dry matter. Conversely, radish (Raphanus sativus L.) and turnip (Brassica rapa L.) roots, in which the activity of the enzyme remained high until maturity, did not store appreciable amounts of sucrose (2% and 9%, respectively, of the dry matter in the mature roots), reducing sugars being the main reserve (more than 80% of the dry matter in mature turnips). The correlation between sucrose content and acid invertase activity was furthermore evident in both sucrose- and hexose-storing roots when the activity of this enzyme was affected by changes in the mineral nutrition. Deficiencies of nitrogen and sulphur reduced the activity of acid and alkaline invertases and led to increase in sucrose content and decrease in reducing sugars. However, the decline of alkaline invertase activity in tissues low in acid invertase had no clear effect on sugar content. Sodium chloride (10(-1)M) affected acid invertase and sugars in a manner similar to that of the two deficiencies, but had practically no effect on alkaline invertase. The changes in sugar content produced by the variations in mineral nutrition were small in hexose-storing roots in relation to those of sucrose-storing roots. It is possible that this result is related to the different levels of acid invertase in the two types of roots.

Effects of Environmental Conditions and the Coadministration of Growth Retardants on the Response of Sugarcane to Foliar Treatment with Gibberellin1

AbstractPoor yields of sucrose from sugarcane are often associated with low sucrose:cane ratios, particularly when climatic conditions tend to favor stem elongation rather than sucrose accumulation. Plant growth regulators may be used to modify environmental effects on the growth of sugarcane and thus alter the balance between utilization and storage of sucrose. The objectives of this study were to investigate the influence of temperature, soil moisture, and the coadministration of plant growth retardants on the response of sugarcane to treatment with gibberellic acid.Single foliar applications of GA (gibberellic acid) commercial sugarcane varieties (interspecific hybrids of Saccharum) stimulated stem elongation for from 2 to 6 weeks, but this response was not reflected in higher cane yields unless the plants were harvested within 6 weeks of treatment. A second application of GA at 4 weeks prolonged the growth response. In the field low temperatures were associated with the more prolonged growth responses, which were of smaller amplitude. Moisture stress had no apparent effect on GA response. No correlations were evident between environmental conditions or application rates and the duration of growth responses in greenhouse trials, but the amplitude increased with application rate within the range of 25 to 200 ppm. Three to five immature or semimature internodes were affected.In field trials under warm conditions a period of growth retardation followed the initial GA‐induced growth stimulation. This did not occur in greenhouse trials. Stem‐sugar concentrations fell during the growthstimulation phase, but recovered as growth rates reduced. Attempts were made to accentuate this recovery, and so to increase the accumulation of sugars, by coadministration of growth retardants with GA. Dalapon had a delayed effect on cane growth, slightly curtailing the duration of the GA response, and suppressing growth thereafter. The phase of growth suppression was accompanied by increased stem sugar concentration in greenhouse‐, but not in field‐trials. Sodium silicate (at up to 200 ppm) had no significant effect on growth or sugar accumulation and did not modify the response to GA. Treatment with azauracil (at up to 400 ppm) strongly inhibited cane growth and increased stem‐sugar concentrations, but showed no significant interaction with GA.