Food reserves of scots pine (Pinus sylvestris L.)

Summary Starch, soluble sugars, triacylglycerols, diacylglycerols and free fatty acids were measured in 30-year-old Scots pine (Pinus sylvestris L.) trees during an annual cycle in the sapwood (youngest ten xylem rings). The radial distribution of carbohydrates and lipids was studied in the trunkwood of 90 -to 150-year-old Scots pine trees collected at the end of the growing season. Determination of the compounds was performed using specific enzymatic assays, capillary gas chromatography and thin layer chromatography. The amounts of glucose, fructose, sucrose, and galactose/arabinose in the sapwood were slightly higher in winter than in summer. Raffinose/stachyose increased up to 5-fold during the cold period. At the beginning of the growing season starch amounts rose, and then decreased in summer and autumn. No concentration changes were observed in the total amounts of diacylglycerols and fatty acids throughout the year. Triacylglycerol levels were slightly higher in February than in summer and autumn. Relative frequencies of individual fatty acids were similar in all lipid fractions. Glucose, fructose, sucrose, starch and triacylglycerols disappeared almost entirely at the transition zone from sapwood to heartwood. In contrast, free fatty acids and galactose/arabinose rose in centripetal direction, and diacylglycerols remained constant across trunk cross-sections. The relative amounts of individual fatty acids changed markedly in the free fatty acid fraction and in the triacylglycerols when crossing the sapwood-heartwood boundary. Concentration changes of reserve materials are discussed in relation to season, mobilization and translocation processes, dormancy, frost resistance, and heartwood formation. The results are compared to those found in needles.     

Formation of heartwood substances in the stemwood of Robinia pseudoacacia L. II. Distribution of nonstructural carbohydrates and wood extractives across the trunk

Summary The distributions of reserve carbohydrates and of three dominant heartwood extractives were determined in the trunkwood of Robinia pseudoacacia L. The trees were cut at different times of the year (September, November, January, and April). With the exception of the tree felled in January, all trunks exhibited highest contents of nonstructural storage carbohydrates (glucose, fructose, sucrose, and starch) in the youngest, outermost sapwood zone. With increasing depth of the trunk, the levels of carbohydrates decreased. At the sapwood-heartwood transition zone, only trace amounts of nonstructural carbohydrates were present. The heartwood itself contained no storage material. The wood zones of different ages of the trees cut in September, November, and January exhibited glucose/fructose ratios of approximately 1. In April, however, there was a shift to glucose. In the youngest sapwood the amounts of soluble sugars were higher in the earlythan in the latewood. Older zones of the sapwood and the sap-wood-heartwood transition zone showed the opposite behaviour. Three main wood extractives of Robinia were characterized and quantified: the flavanonol dihydrorobinetin (DHR), the flavonol robinetin (ROB) and a hydroxycinnamic acid derivative (HCA). Only DHR was present — in very low amounts — in the younger sapwood of all trunks investigated. Higher amounts (>1 mol/g dry weight) of this compound and the HCA were present in the sapwood-heartwood transition zone. DHR augmented within the heartwood up to a more or less constant level. HCA increased towards the heartwood and decreased again in the inner heartwood parts. ROB appeared in the innermost parts of the sapwood-heartwood transition zone and reached maximum values in older parts of the heart-wood. The results indicate that starch is hydrolyzed at the sapwood-heartwood boundary and thus represents a primary major source of hydroxycinnamic acid and flavonoid synthesis.Dedicated to Prof. Meinhart H. Zenk on the occasion of his 60th birthday     

Concentration gradients of free sterols,steryl esters and lipid phosphorus in the trunkwood of Scot's pine (Pinus sylvestris L.)

The amounts of free sterols, steryl esters and lipid phosphorus were determined in the sapwood and heartwood of mature, and in the outer and inner sapwood of young Pinus sylvestris trees. In the mature trees (up to 70 years old) the heartwood contains significantly higher amounts of free sterols than the sapwood. No radial gradient can be demonstrated in the amounts of steryl esters. Lipids extracted from the sapwood contain higher amounts of phosphorus than those from the heartwood. Stems of young Pinus sylvestris trees (up to 13 years old) show in the inner sapwood higher amounts of both free sterols and steryl esters than the peripheral younger wood zone. The inner sapwood of the young stems shows slightly higher amounts of lipid phosphorus than the outer sapwood. The results indicate that Pinus sylvestris accumulates both free sterols and steryl esters in the stems at a very early stage of the life cycle. Sterol accumulation in the innermost parts of the stems seems not to depend on heartwood formation.     

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.     

Food reserves of Scots pine (Pinus sylvestris L.)

Summary The amounts of starch, soluble sugars, triacylglycerols, diacylglycerols and free fatty acids were studied in Scots pine (Pinus sylvestris L.) during an annual cycle in current-year needles and in 1-, 2- and 3-year-old needles collected shortly after bud break. Determination of the compounds was performed using specific enzymatic assays, capillary gas chromatography and thin layer chromatography. Newly emerging needles contained relatively large amounts of starch, but only trace amounts of fat. During autumn and winter, fat content rose, while starch content decreased; amounts of both these reserve materials were very high the next spring shortly before bud break and decreased again during shoot elongation. Concentration of intermediates in triacylglycerol biosynthesis (diacylglycerols and free fatty acids), were low in summer and high in winter. The same pattern was observed for fructose and glucose (the predominant soluble sugars), galactose/arabinose and raffinose/melibiose. In contrast, sucrose concentrations were highest in spring and in autumn. Mature needles of different ages collected in May showed significant differences only in their triacylglycerol and starch content. Concentration changes of reserve materials are discussed in relation to season, mobilization and translocation processes, dormancy, frost resistance and the possibility of carbohydrate-fat interconversions.     

Nonstructural carbohydrates in dormant and afterripened wild oat caryopses

Nonstructural carbohydrates were determined in both embryo and endosperm of dormant (nongerminating) and afterripened (germinating) intact caryopses of wild oat ( Avena fatua L.). No changes in endosperm starch or soluble sugar were observed at the onset of germination (18 h). No changes in glucose, fructose, sucrose or starch within dormant or afterripened embryos correlated with onset of visual germination. In afterripened embryos, depletion of raffinose (18 h), stachyose (18 h) and galactose (24 h) was correlated with germination. In contrast, raffinose-family oligosaccharide levels in dormant embryos remained constant for 7 days following imbibition. Germination of isolated dormant embryos on 88 m M galactose-containing media was accompanied by decreased endogenous levels of raffinose and stachyose. Isolated embryos from dormant caryopses incorporated ¹⁴C from ¹⁴C-fructose into both raffinose and stachyose during 24 h of imbibition. In contrast, no ¹⁴C incorporation into stachyose was observed in embryos from afterripened caryopses. No ¹⁴C incorporation into raffinose was observed at 18 and 24 h. When in vitro activities of α galactosidase were measured, no temporal differences between dormant or afterripened caryopses were detected in either embryo or endosperm tissue. Although the mechanism associated with differences in utilization of raffinose and stachyose is yet unidentified, alterations in raffinose-family oligosaccharide metabolism in the embryo appear to be a unique prerequisite for afterripening-induced germination.     

Steryl glycosides and acylated steryl glycosides ofPinus sylvestris L. sapwood and heartwood

Summary The amounts of steryl glycosides (SG) and acylated steryl glycosides (ASG) were investigated in the sapwood, transition zone, inner heartwood and outer heartwood ofPinus sylvestris L. Only traces of both sterol derivates were present and their amounts decreased slightly towards the heartwood. The amount of SG decreased nearly to zero in the inner heartwood but the amount of ASG in the inner heartwood increased slightly. The suitability of enzymatic methods in SG and ASG hydrolysis, and sterol and glucose quantitative determinations, is discussed.     

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.     

摘除雌花对甜瓜成熟叶片中糖及相关酶活性的影响

甜瓜有果株的成熟叶片中蔗糖、葡萄糖、果糖含量与无果株的无显著差异,水苏糖与棉子糖含量略低于无果株,肌醇半乳糖苷(合成水苏糖的前体)含量显著低于无果株,蔗糖磷酸合成酶(SPS)和肌醇半乳糖苷合成酶活性与无果株的无显著差异,水苏糖合成酶活性显著高于无果株。     

The effect of season of growth on the chemical composition of cambial saps of Eucalyptus regnans trees

Summary Bark was stripped, at monthly intervals, from the stems of ten previously-unsampled trees of Eucalyptus regnans F. Muell. The exposed surfaces of inner phloem and outer xylem yielded phloem and cambial saps which were rapidly frozen. After freeze drying to determine the contents of water and dry-matter, the samples were extracted with 80% ethanol. The main components in this extract are low molecular weight carbohydrates and salts of inorganic acids. The carbohydrates comprise stachyose, raffinose, sucrose, galactinol, glucose, fructose, myo-inositol and galactose; sucrose is invariably the major component. The amounts of all components varied widely during the sampling period. Multiple regression analyses showed that season of growth has a significant effect on sucrose, glucose, fructose, total sugars and soluble dry-matter, maxima being recorded near the beginning of autumn and spring, and minima near the beginning of winter and summer; that oligosaccharide and myoinositol contents are significantly related to atmospheric temperature; and that rainfall has a significant effect on the hexose and total sugar contents, saps from the xylem surfaces being more affected than those from the phloem surfaces. The translocated photosynthates in E. regnans appear to be oligosaccharides of the raffinose family and sucrose. Significant negative correlations between oligosaccharides and both sucrose and myoinositol, and significant positive correlations between sucrose and both glucose and fructose, are consistent with enzymic hydrolysis and resynthesis of most di- and oligosaccharides. The biosynthetic demands of developing secondary tissues and/or the fluctuations in composition of sieve-tube assimilates appear to control the composition of the sugars in the saps. Oligosaccharides and sucrose may function as soluble reserve substances as well as translocated photosynthates. It is possible that myoinositolis a key component in the interconversion processes of the sugars; experiments with radioactive sugars tend to lend support to this contention, especially during winter conditions.     

Hydrolysis and resynthesis of sucrose and related sugars in the developing stem tissues of Eucalyptus regnans trees

Summary When cambial tissues are removed from tree stems of Eucalyptus regnans F. Muell. and incubated in vitro with [¹⁴C]glucose, [¹⁴C]galactose and [¹⁴C]fructose in the presence of sufficient PVP (polyvinylpyrrolidone) radioactive sucrose, members of the raffinose family and related sugars are synthesized. These results suggest that PVP inactivates substances which, in in vitro experiments, inhibit the action of enzymes which are essential to the resynthesis of nutrient sugars (sucrose, raffinose and stachyose). In living trees, such enzyme inhibition is less likely to occur.     

Transport of Stachyose and Sucrose by Vacuoles of Japanese Artichoke (Stachys sieboldii) Tubers

Vacuoles are the stores for large amounts of stachyose [αgal (1,6) αgal (1,6) αglc (1,2) βfru] in tubers of Japanese artichoke (Stachys sieboldii). The uptake of stachyose by these vacuoles was examined and compared with that of sucrose. The uptake mechanisms of both sugars were quite similar. The kinetics showed a single saturable response to increasing external concentrations of ¹⁴C-sugars with similar apparent K_m values of about 50 and 30 millimolar for stachyose and sucrose, respectively. The uptake rates, however, were always higher for stachyose than for sucrose. Stachyose and sucrose uptake was inhibited by fructose and raffinose, and, reciprocally, by sucrose and stachyose, but not by glucose or galactose. The main structural feature common to all sugars recognized by the uptake systems seems to be a terminal fructosyl residue. The uptake of both sugars was stimulated by Mg-ATP and inorganic pyrophosphate, suggesting a proton-sugar antiport system. The possibility that stachyose and sucrose might be transported by the same carrier is discussed.     

Studies on the Carbohydrates of Horse Radish,Cochlearis Armoracia L

In the root of horse radish, sucrose, fructose, glucose and two unknown fructose-oligosac-charides were found in the form of free sugars, in the decreasing order just given, and large amounts of starch, hot 50% methanol-soluble polysaccharide, water-soluble polysaccharide, pectin, hemicellulose, cellulose and a small amount of lignin were found as polysaccharides. As the constructive sugar of these polysaccharides, the following, i.e., glucose, fructose, galactose, arabinose, galacturonic acid and xylose were detected.     

Variation in the amount of triacylglycerols and steryl esters in the outer sapwood of Pinus sylvestris L.

Variation in the amount of triacylglycerols and steryl esters was analysed enzymatically in the outer sapwood of Scots pine (Pinus sylvestris L.). Increment borings were taken at breast height from 40 stems of different diameter. Wood samples from outer sapwood (10 mm from the cambium) were extracted with acetone. Triacylglycerols and steryl esters were separated on TLC and the levels of glycerol and sterol were analysed enzymatically. The average amount of triacylglycerols and steryl esters was approximately 25 and 0.83 mg/g dry weight, respectively. However, variation between the stems studied was fairly large. The sapwood of young and small-diameter stems was not found to store larger amounts of either triacylglycerols or steryl esters than the sapwood of old stems. Neither was there any relationship between the amount of triacylglycerols and steryl esters in the outer sapwood. The possible role of these compounds in heartwood formation is discussed.     

Sugar synthesis and phloem loading in Coleus blumei leaves

Sugar-synthesis and -transport patterns were analyzed in Coleus blumei Benth. leaves to determine where galactinol, raffinose, and stachyose are made and whether phloem loading includes an apoplastic (extracellular) step or occurs entirely within the symplast (plasmodesmata-connected cytoplasm). To clarify the sequence of steps leading to stachyose synthesis, a pulse (15 s) of ¹⁴CO₂ was given to attached leaves followed by a 5-s to 20-min chase: sucrose was rapidly labeled while galactinol, raffinose and stachyose were labeled more slowly and, within the first few minutes, to approximately the same degree. Leaf tissue was exposed to either ¹⁴CO₂ or [¹⁴C]glucose to identify the sites of synthesis of the different sugars. A 2-min exposure of peeled leaf tissue to [¹⁴C]glucose resulted in preferential labeling of the minor veins, as opposed to the mesophyll; galactinol, raffinose and stachyose were more heavily labeled than sucrose in these preparations. In contrast, when leaf tissue was exposed to ¹⁴CO₂ for 2 min for preferential labeling of the mesophyll, sucrose was more heavily labeled than galactinol, raffinose or stachyose. We conclude that sucrose is synthesized in mesophyll cells while galactinol, raffinose and stachyose are made in the minorvein phloem. Competition experiments were performed to test the possibility that phloem loading involves monosaccharide uptake from the apoplast. Two saturable monosaccharide carriers were identified, one for glucose, galactose and 3-O-methyl glucose, and the other for fructose. Washing the apoplast of peeled leaf pieces with buffer or saturating levels of 3-O-methyl glucose, after providing a pulse of ¹⁴CO₂, did not inhibit vein loading or change the composition of labeled sugars, and less than 0.5% of the assimilated label was recovered in the incubation medium. These and previous results (Turgeon and Gowan, 1991, Plant Physiol. 94, 1244–1249) indicate that the phloem loading pathway in Coleus is probably symplastic.Abbreviations 3-OMG 3-O-methyl glucose - PCMBS p-chloromercuribenzenesulfonic acid - SE-CCC sieve-element-companion-cell complex This research was supported by National Science Foundation Grant DCB-9104159, U.S. Department of Agriculture Competetive Grant 90000854, and Hatch funds.     

Carbohydrate Changes during Maturation of Cucumber Fruit : Implications for Sugar Metabolism and Transport

Changes in the carbohydrate profiles in the mesocarp, endocarp, and seeds of maturing cucumber (Cucumis sativus, L.) fruit were analyzed. Fruit maturity was measured by a decrease in endocarp pH, which was found to correlate with a loss in peel chlorophyll and an increase in citric acid content. Concentrations of glucose and fructose (8.6-10.3 milligrams per gram fresh weight, respectively) were found to be higher than the concentration of sucrose (0.3 milligrams per gram fresh weight) in both mesocarp and endocarp tissue. Neither raffinose nor stachyose were found in these tissues. The levels of glucose and fructose in seeds decreased during development, but sucrose, raffinose, and stachyose accumulated during the late stages of maturation. Both raffinose and stachyose were found in the seeds of six lines of Cucumis sativus L. This accumulation of raffinose saccharides coincided with an increase in galactinol synthase activity in the seeds. Funiculi from maturing fruit were found to be high in sucrose concentration (4.8 milligrams per gram fresh weight) but devoid of both raffinose and stachyose. The results indicated that sucrose is the transport sugar from the peduncle to seed, and that raffinose saccharide accumulation in the seed is the result of in situ biosynthesis and not from direct vascular transport of these oligosaccharides into the seeds.     

Variation of non-structural carbohydrates in silver birch (Betula pendula Roth) wood

Non-structural carbohydrates in silver birch (Betula pendula Roth) wood were analysed in a 7-year-old clone and in five mature stems. The analysis was conducted to obtain more detailed information on seasonal fluctuation of these components and of the tree-to-tree variation and within stem variation. The sugars were analysed by GLC-MS. The smallest total soluble sugar amounts (consisting of sucrose, fructose, glucose, raffinose and myo-inositol) in young trees were measured during mid-summer (ca. 0.3%) and the largest while in dormancy (ca. 1.6% on wood dry weight basis). Raffinose was detected in autumn as a minor component. The proportion of monosaccharides and the amount of myo-inositol were largest during growth. Compared to other studies silver birch showed more evident seasonal fluctuation in soluble sugars than evergreen tree species. The sugar amount in mature stems was approximately at the same level as in young trees that had the same felling time. Tree-to-tree variation in the non-structural carbohydrates in the mature wood was fairly large. However, the amount of total soluble sugars, sucrose and glucose showed significant variation within the stem. The amount of these sugars was largest in samples that were taken close to the cambium. Starch was also detected close to pith. According to the heartwood definition and starch measurement results in this paper, it could be stated that silver birch does not form heartwood.     

Digestibility of carbohydrates in growing pigs: a comparison between the t-cannula and the steered ileo-caecal valve cannula

We compared the determination of ileal and total tract digestibility of carbohydrates in five experimental diets using a double 5?×?5 Latin square design involving a total of 10 cannulated pigs; half of the pigs were equipped with a simple T-cannula and the other half with steered ileo-caecal valve (SICV)-cannula. The diets consisted of nitrogen-free mixture and soya bean meal, sunflower meal, peas or rape seed cake diluted to about 180?g/kg DM protein with the nitrogen-free mixture. There was no significant difference in the digestibility values using the two types of cannulas with regard to organic matter, sugars (sum of glucose, fructose and sucrose), α-galactosides (sum of raffinose, stachyose and verbascose), starch, cellulose, total non-cellulosic polysaccharides (NCP) and insoluble NCP constituents. The digestibility values for the NCP residues arabinose and galactose, however, were estimated higher but with a lower variability with the SICV-cannula compared with the T-cannula. The type of cannula did no influence the estimation of the total tract digestibility for any of the major dietary constituents, but the total tract digestibility was slightly more variable when the pigs were equipped with the SICV-cannula compared with the T-cannula. There was no difference in the ileal digestibility of sugars, α-galactosides, cellulose and the NCP arabinose and uronic acids residues among the experimental diets, while the ileal digestibility of starch and the remaining NCP sugar residues varied between diets. The total tract digestibility was complete for sugars, α-galactosides and starch, whereas the digestibility of the cell wall constituents varied in accordance with the polymeric composition of the cell walls. It was concluded that ileal digesta samples from SICV-cannula are more homogenous than those from the T-cannula. In cases where the precision of each determination is crucial, the SICV-cannula should be the option.     

Influence of 2-deoxy-D-glucose upon growth and invertase activity of carrot (Daucus carota L.) cell suspension cultures

Carrot (Daucus carota L.) cell suspension cultures grew well when provided with glucose, fructose, sucrose or raffinose. Galactose and melibiose supported less growth unless supplemented with glucose or fructose. In combination with ten different sugar mixtures, 2-deoxy-D-glucose (dGlc) inhibited culture growth. Inhibitory effects of dGlc were more marked with fructose, melibiose, raffinose or mixtures of these sugars in the culture medium. The presence of glucose or galactose reduced the inhibitory effects of dGlc on culture growth. Experiments with radioactive labelled sugars demonstrated that dGLc uptake was greater in the presence of fructose than glucose, and that growth inhibition of dGlc coincided with its uptake. Reduced protein content was also associated with the inhibitory effects of dGlc. Cultured cells contained lower levels of invertase (EC 3.2.1.26) activity during the active phase of culture growth (up to 25 days after subculture) than when growth had peaked and subsequently declined. Acid and alkaline invertase activities were not greatly reduced by exogenous hexoses. Invertase activity was greatest during periods of low protein content in all cultures and was inhibited by dGlc during the latter phases of the culture period. Free intracellular sugars throughout the culture period consisted mainly of glucose and fructose.