Use of various carbon sources by isolated maple callus cultures

The growth of isolated maple cellus (A. rubnum and A. saccharum)indicated general categories for the use of carbon sources:lactose, melibiose, mannose, maltose-minimal growth; fructose,galactose-limited growth; trehalose, cellobiose, raffinose,glucose, sucrose-good growth. The results also indicated thattissues grew as well on medium containing filter-sterilizedsugars as on medium containing autoclaved sugars. ¹Vermont Agricultural Experiment Station, Journal Series No.320. (Received February 19, 1973; )     

Import of Sucrose and its Partitioning in the Synthesis of Galactomannan and Raffinose-oligosaccharides in the Developing Guar (Cyamopsis tetragonolobus) Seed

Import of sucrose and its transformation to galactomannan andraffinose-oligosaccharides have been studied in the developingguar seed. The amount of galactomannan gradually increased withthe ageing of the seed. During the entire period of pod development,sucrose constituted the major portion of the free sugars inthe seed (both endosperm and cotyledons) as well as in the podwall. Besides myo-inositol, the free sugars detected in thedeveloping endosperm and cotyledons were glucose, fructose,raffinose and stachyose. Some compounds, possibly glycosides(RG values higher than that of fructose), were also detectedin the endosperm. In the later stages of seed development, therelative proportion of raffinose in the free sugars increased,reaching 50% of the total free sugars in 77-d-old cotyledons.With pod maturity, the activities of soluble acid and boundacid invertases in the pod wall increased manifold with a concomitantdecline in the non-reducing sugar content. These enzymes seemto be involved in the mobilization of sucrose from this fruitingstructure into the seed. An increased synthesis of raffinose-oligosaccharidesboth in the endosperm and cotyledons was associated with highactivities of soluble acid invertase (pH 4.8) and sucrose-UDPglucosyl transferase in these tissues. Feeding uniformly labelled¹⁴C-sugars to the detached intact pods as well as to the isolatedendosperm and cotyledons resulted in labelling of all endogenousfree sugars and galactomannan. The uptake and incorporationinto galactomannan of ¹⁴C was stimulated by Co²⁺, Mn²⁺ and Mg²⁺.Except for mannose, a major proportion of the ¹⁴C from glucose,fructose and sucrose appeared in sucrose in both endosperm andcotyledons indicating a fast reconstitution of sucrose in situ.Based on the present results, a possible mode of transformationof sucrose to galactomannan and raffinose-oligosaccharides hasbeen proposed. Key words: Sucrose, galactomannan, raffinose-oligosaccharides, invertase, sucrose-UDP glucosyl transferase, ¹⁴C-incorporation, guar seed     

Effects of six sugars on the longevity,fecundity and nutrient reserves of Microplitis mediator

Parasitoid adults can directly feed on floral nectar and honeydew containing monosaccharides and disaccharides. Oligosaccharides such as maltose, melezitose and raffinose are also found in honeydew but are rare in floral nectar. The effects of six different sugar resources on the longevity, fecundity and nutrient reserves of Microplitis mediator, a larval endoparasitoid in the cotton bollworm Helicoverpa armigera (Hübner) were determined in our laboratory. The results showed that both food and sex affected longevity of this wasp. Females and males of M. mediator fed with 1 M sucrose solution survived longer than controls fed with water (5.7- and 3.7-fold longer, respectively). When provided with sucrose, glucose or fructose solutions, the parasitoid generated 3.6- to 3.7-fold more offspring than controls, and 60–75% of these progenies were produced during the first 5 days. When separately given fructose, sucrose or glucose, this wasp accumulated fructose and total sugar at the highest level, which means a high sugar levels might lead to prolonging longevity and more offspring in M. mediator. In addition, compared with organisms fed galactose or raffinose, M. mediator fed sucrose or fructose accumulated high glycogen levels. Furthermore, in M. mediator, the lipid content declined with the advancing age. Females showed the slowest lipid metabolic rates when fed with sucrose, glucose, fructose, mannose and galactose solutions versus when fed with raffinose and control. In addition, only sucrose had a significant effect on lipid levels in males nearing the end of life.     

Sexual process in eight-spored ascus-forming yeast, Schizosaccharomyces japonicus I. Culture medium for the synchronous sexual process

The sexual process of Schizosaccharomyces japonicus consistsof sexual flocculation, zygote formation, eight-spored ascusformation and liberation of spores from the ascus. The culturemedium in which this sexual process took place synchronouslywas prepared. For the completion of the sexual process, glucosewas essential and inorganic salts and vitamins were also required.Elimination of the nitrogen source stimulated the rate of sporeformation. The temporal relationship among the sexual eventswas also elucidated: sexual flocculation, zygote formation,ascus formation and spore liberation occurred at 4, 7, 13 and20 hr, respectively, after transfer to the medium for the synchronoussexual process. (Received May 11, 1978; )     

Extracellular invertase of Rhizobium japonicum and its role in free sugar metabolism in the developing root nodules of Sesbania grandiflora

Extracellular invertase of Rhizobium japonicum and its role in free sugar metabolism in the developing root nodules of Sesbania grandiflora L. was studied. The enzyme hydrolysed sucrose extracellularly, and its release was substrate inducible. 0.1 Mβ-mercaptoethanol released the cell-bound form of this enzyme. The production of invertase was low when glucose, galactose, mannose, fructose and raffinose were used as carbon sources in the growth medium. In the developing nodules sucrose was the major sugar. The content of fructose was low in comparison with that of glucose – suggesting that in the nodules, fructose is converted to glucose prior to its entry into the bacterial cell. The content of glucose synchronised with the pattern of change in the activity of invertase in the nodules.     

Changes in the pool of soluble sugars induced by dehydration at the heterotrophic phase of growth of wheat seedlings

Loss of dehydration tolerance coincides with a shift from heterotrophy to autotrophy during post-germination growth of spring wheat seedlings. This critical stage falls on the fifth day following imbibition. Till the sixth day of experiment light had no effect on dry weight of the seedlings but the survival of six day old seedlings was reduced by half upon dehydration. Germinating seeds in the presence of 5 mM glucose, fructose, mannose or sucrose did not promote seedling growth but either increase (glucose, fructose) or decreased (mannose, sucrose) the survival of dehydrated seedlings. Protection against dehydration by the former sugars was correlated, irrespective of the seedling age, with the decrease of sugar pool in seeds and increase in shoots (coleoptile and first leaf) and roots. The opposite changes were provoked by the sugars hampering seedling survival. Generally, survival of wheat seedlings was not correlated with the size of soluble sugar pool but its distribution and composition. Lower mobilisation of soluble sugars in seed, lower proportion of reduced sugars to sucrose and higher share of raffinose is characteristic for the tolerant four day old seedlings and those grown in the media containing glucose or fructose. The results presented indicate that higher proportion of reduced sugars to sucrose and lower share of raffinose in six day old seedlings seems to be associated with the loss of dehydration tolerance of these seedlings, despite heterotrophic character of growth.     

Effect of glucose on sporulation and extracellular amylase production byClostridium perfringens type A in a defined medium

The effect of glucose and other sugars on sporulation and extracellular amylase production byClostridium perfringens NCTC 8679 type A in a defined medium was studied. Cells grown in the presence of glucose and mannose yielded the highest levels of amylase activity, while disaccharides such as lactose, maltose, and sucrose resulted in moderate amylase production. Little amylase activity was detected in the medium in the presence of ribose or galactose. The concentration of each sugar resulting in highest amylase production was between 6 and 10mm except for fructose (25mm). Levels of heat-resistant spores decreased as sugar concentrations increased. The addition of even small amounts of glucose to the medium before exponential growth suppressed sporulation but maximized amylase activity. The addition of glucose after the initiation of sporulation did not inhibit spore formation. However, its addition to 3-h amylase-producing cells did inhibit subsequent sporulation but promoted the continued excretion of amylase. The different response to glucose between sporulating cells and amylase-producing cells suggests that the mechanisms of catabolite repression of extracellular amylase production and sporulation are distinct in this strain ofC. perfringens.     

Carbon catabolite repression of invertase during batch cultivations of Saccharomyces cerevisiae: the role of glucose, fructose, and mannose

When Saccharomyces cerevisiae are grown on a mixture of glucose and another fermentable sugar such as sucrose, maltose or galactose, the metabolism is diauxic, i.e. glucose is metabolized first, whereas the other sugars are metabolized when glucose is exhausted. This phenomenon is a consequence of glucose repression, or more generally, catabolite repression. Besides glucose, the hexoses fructose and mannose are generally also believed to trigger catabolite repression. In this study, batch fermentations of S. cerevisiae in mixtures of sucrose and either glucose, fructose or mannose were performed. It was found that the utilization of sucrose is inhibited by concentrations of either glucose or fructose higher than 5 g/l, and thus that glucose and fructose are equally capable of exerting catabolite repression. However, sucrose was found to be hydrolyzed to glucose and fructose, even when the mannose concentration was as high as 17 g/l, indicating, that mannose is not a repressing sugar. It is suggested that the capability to trigger catabolite repression is connected to hexokinase PII, which is involved in the in vivo phosphorylation of glucose and fructose. Received: 5 May 1998 / Received revision: 3 August 1998 / Accepted: 8 August 1998     

Changes in soluble carbohydrates and starch amounts during somatic and zygotic embryogenesis of Acca sellowiana (Myrtaceae)

Comparative analysis of zygotic and somatic embryogenesis of Acca sellowiana showed higher amounts of sucrose, fructose, raffinose, and myo-inositol in zygotic embryos at different developmental stages than in corresponding somatic ones. These differences were mostly constant. In general, glucose levels were significantly lower than the other soluble carbohydrates analyzed, showing minor variation in each embryo stage. Despite the presence of sucrose in the culture medium, its levels conspicuously diminished in somatic embryos compared with the zygotic ones. Raffinose enhanced parallel to embryo development, regardless of its zygotic or somatic origin. Analysis of the soluble carbohydrate composition of mature zygotic cotyledon used as explant pointed out fructose, glucose, myo-inositol, sucrose, and raffinose as the most important. Similar composition was also found in the corresponding somatic cotyledon. Total soluble carbohydrates varied inversely, decreasing in zygotic embryos and increasing in somatic embryos until the 24th d, at which time they increased rapidly about sixfold in zygotic embryos until the 27th d, a period coinciding with the zygotic proembryos formation. Such condition seems to reflect directly the variation of endogenous sucrose level, mainly because glucose and fructose diminished continuously during this time period. This means that, in terms of soluble sugars, zygotic embryo formation occurred under a situation represented by high sucrose amounts, simultaneously with low fructose and glucose levels, while in contrast, somatic embryo formation took place under an endogenous sugar status characterized by a substantial fructose enhancement. Starch levels increased continuously in zygotic embryos and decreased in somatic ones, the reverse to what was found in fructose variation. Starch accumulation was significantly higher in somatic torpedo and cotyledonary embryos than in the corresponding zygotic ones.     

Temporal Changes of Floral Nectar-sugar Composition in Polyscias sambucifolia (Sieb. ex Dc.) Harms (Araliaceae)

Polyscias sambucifolia (Sieb. ex DC.) Harms, an endemic Australianspecies of the Araliaceae, is strongly dichogamous and andromonoecious.Petals and stamens are present only in the male sexual phase,although nectar is secreted in both the male and female sexualphases. This study characterised the changes of the major nectar-sugarssecreted in each sexual phase. The implications of such shiftsin nectar composition with respect to the morphological dissimilarityof the two sexual phases are considered. Field based sampling with HPLC analysis was employed to characterisethe major sugar content of nectar. During flowering, nectarconsisted of equal amounts of fructose and glucose, with negligibleamounts of sucrose. There was statistically significant variationin the concentration of fructose and glucose in each sexualphase. Male phase nectar had approximately 6% of the sugar concentrationof the female phase nectar in hermaphrodite flowers. The effectof pollination upon nectar secretion was also investigated.Hand pollinations resulted in an attenuated nectar secretionduration and the production of nectar with a reduced sugar content.Copyright1994, 1999 Academic Press Pollination, nectar sugar composition, fructose, glucose, sucrose, HPLC, Polyscias sambucifolia, Elderberry Panax, Araliaceae     

Characterization of Hexose Transporter for Facilitated Diffusion of the Tonoplast Vesicles from Pear Fruit

Tonoplast vesicles were prepared from the flesh tissue of maturepear fruit. Sugar uptakes into the vesicles determined by twodifferent methods, the membrane and the gel filtration methods,were quite similar. The uptake was highest for glucose and subsequently,in order, for fructose, sucrose and sorbitol. It was not stimulatedby addition of ATP, although the vesicles could create a protongradient. However, the uptakes were significantly inhibitedby p-chloromercuribenzene sulphonate (PCMBS, SH-reagent andinhibitor of sugar transporter). Further, the PCMBS-sensitiveuptakes of glucose and fructose saturated with their increasedconcentrations. Thus, these PCMBS-sensitive uptakes are mediatedby the transporter of facilitated diffusion. The uptakes ofglucose or fructose each had two K_m values. K_m values for glucosewere 0.35 and 18 mM, and those for fructose were 1.6 and 25raM. The uptake of 0.2 mM glucose was inhibited by 2 mM fructoseand that of 2 mM fructose was inhibited by 2 mM glucose, butneither was inhibited by sucrose or sorbitol. O-methyl-glucose(OMG) also inhibited both the glucose and fructose uptakes.Therefore, the same transporter may mediate both glucose andfructose uptakes at lower concentrations; this hexose transportsystem differed from the sucrose and sorbitol transport systems. ¹Research Fellow of the Japan Society for the Promotion of Science. ²Present address: Faculty of Agriculture, Tohoku University,1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, 981 Japan.     

The metabolism of galactose and the raffinose oligosaccharides by germinating bambarra groundnut seeds

Stachyose is present in the highest amount in the soluble sugar fraction of dry bambarra groundnut cotyledons, followed in descending order by raffinose, sucrose and verbascose. During germination in the dark, the stachyose and raffinose content decrease rapidly, but there is little change in the relatively small amount of verbascose present. The sucrose content increases rapidly during the first two weeks and decreases thereafter. Free glucose and fructose were present in the cotyledons after the 7th day and gradually increased in amount with time of germination. Free galactose and other galactose-containing oligosaccharides were not detected in either the dry or germinated bambarra seeds. During germination, galactose was the only identifiable sugar, aside from traces of sucrose, glucose and fructose, in the extracted soluble sugar fraction in the embryonic axes of all ages when the tissue was incubated with D-[1¹⁴C] galactose. With the cotyledons, however, most of the radioactivity was in glucose and fructose during the early period of germination and in sucrose later. A small fraction of the radioactivity was lost as CO₂.     

Different effects of galactose and mannose on cell proliferation and intracellular soluble sugar levels in <Emphasis Type="Italic">Vigna angularis</Emphasis> suspension cultures

Plant cells utilize various sugars as carbon sources for growth, respiration and biosynthesis of cellular components. Suspension-cultured cells of azuki bean (Vigna angularis) proliferated actively in liquid growth medium containing 1% (w/v) sucrose, glucose, fructose, arabinose or xylose, but did not proliferate in medium containing galactose or mannose. These two latter sugars thus appeared distinct from other sugars used as growth substrates. Galactose strongly inhibited cell growth even in the presence of sucrose but mannose did not, suggesting a substantial difference in their effects on cell metabolism. Analysis of intracellular soluble-sugar fractions revealed that galactose, but not mannose, caused a conspicuous decrease in the cellular level of sucrose with no apparent effects on the levels of glucose or fructose. Such a galactose-specific decrease in sucrose levels also occurred in cells that had been cultured together with glucose in place of sucrose, suggesting that galactose inhibits the biosynthesis, rather than uptake, of sucrose in the cells. By contrast, mannose seemed to be metabolically inert in the presence of sucrose. From these results, we conclude that sucrose metabolism is important for the heterotrophic growth of cells in plant suspension-cultures.     

Changes in concentrations of soluble carbohydrates during germination of <Emphasis Type="Italic">Amaranthus caudatus</Emphasis> L. seeds in relation to ethylene,gibberellin A<Subscript>3</Subscript> and methyl jasmonate

Unimbibed Amaranthus caudatus seeds were found to contain stachyose, raffinose, verbascose, sucrose, galactinol, myo-inositol, glucose and fructose, while no galactose, maltose and maltotriose was detected. During imbibition, seed concentrations of verbascose, stachyose, raffinose, galactinol, myo-inositol (temporary) and fructose (transient) were observed to decrease; concentrations of galactose and maltose remained fairly constant, while those of sucrose, glucose and maltotriose increased, the increase in sucrose concentration was only temporary. Effects of gibberellin A₃ (GA₃) at 3 × 10⁻⁴ M and ethephon at 3 × 10⁻⁴ M alone or in the presence of methyl jasmonate (Me-JA) at 10⁻³ M on concentrations of soluble sugars during germination of A. caudatus seeds were examined. Me-JA was found to inhibit seed germination and fresh weight of the seeds, but did not affect sucrose, myo-inositol, galactose and maltose concentrations during imbibition for up to 20 h. The exogenously applied GA₃ was observed to enhance germination, stachyose breakdown and glucose concentration after 20 h of incubation. Ethephon stimulated seed germination as well as utilisation of stachyose, galactinol (both after 14 and 20 h) and raffinose (after 14 h of incubation). Although the stimulatory effect of either GA₃ or ethephon on seed germination was blocked by Me-JA; these stimulators increased mobilisation of raffinose and stachyose, but only ethephon enhanced both glucose and fructose after 14 and/or 20 h of incubation in the presence of Me-JA. The maltose concentration was increased by both GA₃ and ethephon alone and in the presence of Me-JA. Of the growth regulators studied, ethephon alone and/or in combination with Me-JA significantly increased the concentrations of glucose, fructose, galactose, maltose and maltotriose. The differences in sugar metabolism appear to be linked to ethylene or GA₃ applied simultaneously with Me-JA.     

Studies on Pyricularia oryzae Cav. in Sierra Leone: Morphological and Physiological Variability of Some Isolates

The morphological and physiological variability of six isolatesof Pyricularia oryzae, the causal organism of rice blast disease,were investigated. The rate of growth, colony characters, andtime of sporulation were found to vary with the different isolatesthough not by appreciable amounts. Each of the isolates showedconsistently better growth on Takahashi's B medium than on Czapek-Dox'smedium although the growth trend was the same in both media.The colony characters developed by each isolate are not dependenton the medium on which it is growing—a pointer to thefact that such characters may be genetically controlled. Germinationwas faster in distilled water than in 2 per cent agar. All theisolates produced appresoria in vivo and in vitro; those producedin vivo were, however, considerably larger than those producedin vitro. On the basis of appresorial types, the isolates werefound to fall into two physiological races—smooth-walledand rough-walled. Each isolate produced consistently only oneappresorial type in vitro from the apical or basal cell of theconidium. The utilization of carbon and nitrogen compounds variedfrom one isolate to the other, carbon compounds being generallybetter utilized than nitrogen compounds. Pyricularia oryzaecan metabolize a wide range of carbon compounds. However, mannose,sucrose, glucose, fructose, and maltose proved to be most suitablecarbon sources. The variations in the utilization of the variouscarbon and nitrogen compounds seem to reflect inherent biochemicaland physiological differences among the isolates.     

Uptake and Metabolism of Sugars by Suspension Cultured Catharanthus roseus Cells

The uptake and metabolism of sugars by suspension-cultured Catharanthusroseus cells were investigated. Substantially all the sucrosein the culture medium was hydrolyzed to glucose and fructosebefore being taken up by the cells. The activity of invertasebound to cell walls, determined in situ, was high at the earlystage of culture. Glucose was more easily taken up by the cellsthan was fructose. Tracer experiments using [U-¹⁴C]glucose and[U-¹⁴C]fructose indicated that glucose is a better precursorfor respiration than fructose, while fructose is preferentiallyutilized for the synthesis of sucrose, especially in the earlyphase of cell growth. Possible metabolic routes of sugar insuspension-cultured Catharanthus roseus cells are discussedin the context of these results. Catharanthus roseus, Madagascar periwinkle, suspension culture, sucrose, glucose, fructose, metabolism, glycolysis     

Feeding responses by female Pieris brassicae butterflies to carbohydrates and amino acids

Most Lepidoptera feed during the adult stage on carbohydrate‐rich food sources, primarily floral nectar. However, little is known about the factors leading to the acceptance of a possible food source. It is reported that butterflies select for nectar rich in sucrose and amino acids. This suggests that the insects have developed a sensitivity to these nectar compounds. We tested females of the large cabbage white, Pieris brassicae L. (Lepidoptera: Pieridae) for their responses to 10 different nectar‐ or honeydew‐sugars after either tarsal or proboscis stimulation. In no‐choice experiments, food‐deprived P. brassicae showed the strongest response to sucrose, followed by fructose. Other sugars, including galactose, glucose, maltose, mannose, melezitose, melibiose, raffinose and trehalose, did not elicit a feeding response. Mixtures of essential or common non‐essential amino acids did not stimulate feeding. In a choice situation, P. brassicae preferred sucrose over fructose, whereas they accepted a sucrose and amino acid solution equally to a plain sucrose solution. The results indicate that for P. brassicae, feeding is mainly elicited by sucrose and fructose.     

Seasonal Variations in the Carbohydrates in the Xylem of Antiaris africana

The xylem of Antiaris africana contains sucrose, starch, glucose,fructose, maltose, and raffinose. Sucrose and starch are themost abundant carbohydrates. Glucose and fructose occur in relativelyequal amounts while maltose and raffinose are the least abundant.Raffinose disappears from the xylem during the dry season, justbefore leaf fall. The pattern of seasonal variation in the individualsugars and starch is similar. There is generally a peak at leaffall and a depletion of these reserves at new flush. Accumulationof carbohydrates during leaf fall occurs first in the youngestxylem (i.e. the 0–2-cm segment). The youngest xylem alsoaccumulates the greatest amount of reserve sugars and starch.The concentrations of the sugars decrease inwards until theybegin to rise after the 4–6-cm segment. There is, however,no such rise in the concentration of starch. The dry-mattercontents increase inwards from the youngest xylem until theylevel out after the 4–6-cm segment. There is a rapid fallin the sucrose and starch contents of felled A. africana. Sucrosedropped by about 65 per cent and starch by about 73 per centin the first 10 days after felling. The levels of other sugarsdecreased gradually except for glucose and fructose which initiallyrose and then fell. Glucose and maltose could still be detectedon the 68th day after felling.     

Degradation of the endosperm cell walls of Lactuca sativa L., cv. Grand Rapids

The timing of mobilisation of lipid, sucrose, raffinose and phytate in lettuce seeds (achenes) (cv. Grand Rapids) has been examined. These reserves (33%, 1.5%, 0.7%, 1.4% of achene dry weight, respectively) are stored mostly in the cotyledons. Except for a slight degradation of raffinose and increase in sucrose, there is no detectable reserve mobilisation during germination. The endosperm (8% of seed dry weight), which has thick, mannan-containing cell walls (carbohydrate, 3,4% of seed dry weight), is completely degraded within about 15h following germination. Mannanase activity increases about 100-fold during the same period and arises in all regions of the endosperm. Also during this period sucrose and raffinose are degraded and fructose and glucose accumulate in the embryo. The endosperm hydrolysis products are taken up by the embryo, and are probably used as an additional reserve to support early seedling growth. However, endosperm cell-wall carbohydrates, such as mannose, are not found as free sugars. Lipid and phytate are degraded in a later, second phase of mobilisation. Low levels of sucrose are present in the embryo, mostly in the cotyledons, and large amounts of fractose and glucose (14% of seedling dry weight at 3 days after sowing) accumulate in the hypocotyl and radicle. It is suggested that sucrose, produced in the cotyledons by gluco-neogenesis, is translocated to the axis and converted there to fructose and glucose.     

Sugars in Natural and Artificial Pollen Germination Substrates

The stigmatic exudates and pollen grains of five unrelated specieswere tested for sugars. Glucose, fructose, and sucrose werefound in the stigmatic fluid of Yucca aloifolia L. and glucoseand fructose in that of Oenothera adrummondii Hook. In in vitroexperiments with Y. aloifolia pollen, high germination percentageswere obtained in artificial media containing glucose or sucrose.Fructose, which is present in the stigmatic fluid of the Yuccasp. resulted in high in vitro pollen germination only when borateand calcium were added to the medium. Presence of bound sugarsis indicated in the stigmatic secretion of Citrus aurantiumL. and pollen of the single plant tested germinated at a lowpercentage in artificial sugar media. No sugars were detectedin the stigmatic fluids of Hemerocallis fulva L. and Zea maysL. and in these two species in vitro pollen germination in sugarymedia was negligible or absent. The pollen grains of all five species contain sucrose and thoseof Oenothera and Citrus also reducing sugars.