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  • 1
    Monograph available for loan
    Monograph available for loan
    Leiden : Backhuys Publ.
    Call number: M 09.0014
    Type of Medium: Monograph available for loan
    Pages: VI, 565 S. , Ill., graph. Darst., Abb.
    ISBN: 9073348676
    Location: Upper compact magazine
    Branch Library: GFZ Library
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  • 2
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In the present field study we analysed the seasonal pattern of carbohydrate composition and contents in the xylem sap of Viscum album and the xylem sap of a deciduous (Populus×euramericana) and a coniferous (Abies alba) host tree species. The results were compared with the soluble carbohydrate composition and contents of mistletoe tissues. On both hosts significant amounts of glucose, fructose, and sucrose were found in the xylem sap of Viscum throughout the seasons. The general seasonal pattern of sugar contents, i.e. high concentrations in spring and lower concentrations in other seasons on Populus, and intermediate concentrations throughout the year on Abies, largely reflected the xylem sap carbohydrate composition and contents of the respective host. These observations provide indirect evidence for carbohydrate flux from the xylem sap of the host into the mistletoe. However, in both hosts xylem sap seems to be deviated into the mistletoe without specific control of carbohydrate flux. Differences observed between the seasonal pattern of xylem sap carbohydrate concentrations in Viscum on Populus and Abies may originate from the different time of leaf development of these species. A clear-cut seasonal pattern of soluble carbohydrates was not observed in the leaves of Viscum on both hosts. Still soluble carbohydrates seem to be reallocated from the senescing to the newly developed leaves of Viscum indicating that the seasonal requirement of carbohydrate for growth and development can only completely be met by carbohydrate acquisition from the host and their own photosynthesis.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The emission of the tropospheric trace gas acetaldehyde was determined in leaves of 4-month-old poplar trees (Populus tremula×P. alba) grown under controlled environmental conditions in a greenhouse. Using a dynamic cuvette system together with a high sensitivity laser-based photoacoustic detection unit, rates of acetaldehyde emission were measured with the high time resolution of about 15 min. Submergence of the roots resulted in the emission of acetaldehyde by the leaves. The emission increased linearly before reaching more or less steady-state values (ca 350 nmol m−2 min−1; ca 470 ng g−1 dry weight min−1) after approximately 6 h. Prolonged flooding of poplar trees resulted in a clear diurnal rhythm of acetaldehyde emission. The emission rates decreased when the light was switched off in the evening and peaked in the morning after the light was turned on again. This pattern significantly correlated with diurnal rhythms of stomatal conductance, photosynthesis, transpiration and with the concentrations of ethanol, the assumed precursor of acetaldehyde, in the xylem sap of flooded poplar trees. It may be concluded that under conditions of diminished stomatal conductance, acetaldehyde emission declines because its diffusive flux is reduced. Alternatively, reduced transpiration may decrease ethanol transport from the roots to the shoots and appreciable amounts of the acetaldehyde precursor ethanol are lacking in the leaves. The present results support the view that acetaldehyde emitted by the leaves of plants is derived from ethanol produced by alcoholic fermentation in submerged roots and transported to the leaves with the transpiration stream.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In numerous locations in Europe spruce trees are exposed to high loads of nitrogen. The present study was performed to characterize the distribution of nitrogen compounds under these conditions. For this purpose Norway spruce (Picea abies [L.] Karst.) trees were cultivated under close-to-natural conditions of a forest understory in soil from an apparently nitrogen-limited field site in the Black Forest either with, or without supplementation of nitrogen as ammonium nitrate. After 11 and 20 months, growth, total nitrogen contents of the biomass, and total soluble non-proteinogenic nitrogen compounds (TSNN, i.e. nitrate, ammonium, soluble proteinogenic and non-proteinogenic amino compounds) in needles, xylem sap and phloem exudate were analysed. After 20 months of growth, N-fertilization had slightly enhanced the biomass of current-, but not of 1-year-old shoots. At both harvests, total N-content of 1-year-old needles was increased by N-fertilization, whereas current-year needles were not significantly affected. By contrast, TSNN was elevated by N-fertilization in both current-year and 1-year-old needles. The increase in TSNN was mainly attributed to an accumulation of arginine. Xylem sap analysis showed that the increase in TSNN of the needles was a consequence of enhanced nitrogen assimilation of the roots rather than the shoot. Since also TSNN in phloem exudates was enhanced, it appears that N-fertilization elevates the cycling pool of amino compounds in young Norway spruce trees. However, this pool seems to be subject to metabolic interconversion, since mainly glutamine and aspartate are transported in the xylem from the roots to the shoot, but arginine accumulated in the needles and the phloem.
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  • 5
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Five-week-old wheat plants were exposed, under controlled environmental conditions, to 60 nl 1−115NO2 or to purified air. After 48 and 96 h of exposure, leaves, stalks and roots were analysed for 15N-enrichment in α-amino nitrogen of soluble, free amino acids. In addition, the in vitro nitrate reductase (NR, EC 1.6.6.1) and nitrite reductase (NIR, EC 1.7.7.1) activities were determined in the leaves. NR activity in the leaves decreased continously during the 96-h exposure to purified air. In the leaves exposed to 15NO2, NR activity increased within the first 24 h, then decreased, and reached the level of controls after 96 h. NiR activity in leaves exposed to purified air was almost constant during the 96-h exposure. In leaves exposed to 15NO2, NiR activity increased within the first 48 h, then decreased, and reached the level of controls after 72 h, Exposure to 15NO2 enhanced the total content of soluble, free amino acids in all tissues analysed. Most of this increase was attributed to Glu in the leaves and to Asn plus Gln the α-amino group of soluble, free amino acids was observed in the leaves, the lowest enrichment in the roots. The main labelled amino compounds were Glu (with 8.0%15N enrichment compared to the control), γ-aminobutyric acid (GABA; 7.9%), Ala (7.2%). Ser (6.8%), Asp (5.5%) and Gln (4.6%). Appreciable incorporation of 15 into Asn was not found. After 96 h exposure to 15NO2 the 15N enrichment in the α-amino group of soluble, free amino acids in the leaves declined as compared to the values obtained after 48 h fumigation. The possible pathway and the time course of 15N incorporation into soluble, free amino acids from the 15NO2 absorbed are discussed.
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  • 6
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In heterotrophic tobacco cells (Nicotiana tabacum L. cv. Samsun) inhibition of sulfate transport by reduced glutathione (GSH) is a reversible process. When GSH was removed from the culture medium subsequent to a 10-h treatment with 1 mM GSH, sulfate transport began to recover after a lag period of ca 4 h and reached the transport rates of controls without GSH within another 3–4 h. Recovery was prevented when inhibitors of protein synthesis, i.e. cycloheximide or puromycin, were added to the medium upon removal of GSH, even if low concentrations (cycloheximide 1 μM; puromycin 250 μM) were applied. At these low concentrations the rate of synthesis of sulfate transport entities was maintained at the rate of degradation in the absence of GSH. The post-transcriptional polyadenylation inhibitor cordycepin and the transcription inhibitor α-amanitin only slightly reduced recovery of sulfate transport from inhibition by GSH. Apparently, protein synthesis is required for this recovery, suggesting that inhibition of synthesis of sulfate carrier entities is the mechanism of action of GSH on sulfate transport in heterotrophic tobacco cells. An initial rate of net increase in sulfate transport during recovery from inhibition of GSH of 3.6±0.2 U h−1 was calculated [1 U=1 nmol sulfate (g DW)−1 min−1]. This rate of increase is small compared with the rate of decrease in sulfate transport at maximum inhibition by cycloheximide (110±3 U h−1). However, with increasing time of exposure without GSH, the net increase in sulfate transport was enhanced to a maximum rate of 96±3 U h−1, measured 5–7 h after GSH had been removed from the media. Apparently, the rate of synthesis of sulfate transport entities in heterotrophic tobacco cells is about twice its rate of degradation.
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  • 7
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: γ-Glutamyl-transpeptidase activity (EC 2.3.2.2) was found in ammonium sulfate precipitates of extracts from cultured cells of Nicotiana tabacum L. var. Samsun. Specific activity up to 3.2 nmol (mg protein)−1 min−1 was achieved, using the artificial substrate γ-glutamyl-p-nitroanilide (Km 0.6 mM) instead of glutathione. Optimal enzyme activity was obtained at pH 8.0–8.5 and 45°C. The enzyme reaction was inhibited competitively by γ-glutamyl analogs (6-diazo-5-oxo-L-norleucine: Ki 0.76 μM; L-azaserine: Ki 0.23 mM) or the inorganic ion m-periodate (Ki 0.43 mM). Cell fractionation and in vivo experiments revealed that 77% of the γ-glutamyl-transpeptidase activity is localized in the soluble cytoplasmic fraction, while 20–23% of the enzyme is found on the outer surface of the plasmalemma.
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  • 8
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Steinkamp, R., Schweihofen, B. and Rennenberg, H. 1987. γ-Glutamylcyclotransfer-ase in tobacco suspension cultures: Catalytic properties and subcellular localization.γ-Glutamylcyclotransferase activity (EC 2.3.2.4) in ammonium sulfate precipitates (40–70% saturation) of extracts from cultured tobacco cells (Nicoliana tabacum L. cv. Samsun) was analyzed as liberation of 5-oxo-proline from L-γ-glutamyl dipeptides. The enzyme was highly specific for the sulfur containing γ-glutamyl dipeptides γ-glutamyl-L-methionine and γ-glutamyl-i.-cysteine. Maximum activity was obtained at pH 8.7 and 35°C. As also observed with animal γ-glutamylcyclotransferase, the tobacco enzyme exhibited a relatively low substrate affinity (γ-glutamyl-i.-methionine: Km 2.2 ± 0.4 mM). In contrast to animal γ-glutamylcyclotransferase, the tobacco enzyme was not inhibited by the D-isomerof the substrate D-γ-glutamyl-i.-methionine; it also did not use the D isomer as a substrate. γ-Glutamylcyclotransferase of tobacco cells was shown to be a soluble enzyme entirely localized in the cytoplasm.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 98 (1996), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Three-year-old beech trees were fed 35S-sulphate in August 1993 via a flap in a mature leaf of an upper branch. Harvest of beech trees was performed 24 h after feeding 35S-sulphate, before leaf senescence, after leaf abscission, in early winter (January 1994). in late winter (March 1994). before bud break and after bud break. Twenty-four h after feeding 35S-sulphate, 0.7 ± 0.5% of the 35S-radioactivity taken up was exported out of the fed leaf. When trees were analysed 2 months later, i.e., before leaf senescence, this value had increased to 22 ± 7%. The exported 35S-radioactivity was located in the branch containing the fed leaf (2.8 ± 13%). in basipetal parts of the trunk (41 ± 77%) and in the main rool (21 ± 6%). Leaves and apical parts of the trunk were no sink organs for the exported sulphur. Along the tree axis the main proportion of the radiolabel was located in the wood, predominantly in the acid soluble fraction. In the bark the greater portion of the radiolabel was found in the acid insoluble fraction. In both tissues the bulk of the 35S of the soluble fraction was sulphate together with small amounts of glutathione. This pattern did not change until bud break. After bud break, basipetal parts of the trunk lost part of its 35S-radioactivity. Of the 35S-radioactivity which had been exported out of the fed leaf during the previous autumn, 16 ± 2% remained in the trunk, whereas 47 ± 7% of the 35S was found in branches, mainly in the newly developed leaves. The present results show that sulphur, mainly in the form of sulphate, is stored along the tree axis in both bark and wood of beech trees and is re-mobilised during leaf development in spring.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 95 (1995), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 35S-L-cysteine was fed to a mature leaf of 3-year-old beech trees via a flap. After 1 to 4 h the distribution of 35S-radioactivity was analysed in the leaves as well as the bark and wood of the trunk and the main root. Transport of 35S out of the fed leaf amounted to 0.3–1.2% of the total 35S taken up. The branches of the trees did not act as sink organs for the exported radioactivity. The main portion of the 35S-radioactivity transported out of the fed leaf was found in basipetal parts of the trunk. Only a small portion of 35S-radioactivity was transported in acropetal direction. The distribution of the 35S-radioactivity within the trunk showed a higher portion of 35S in the bark than in the wood. In both tissues, bark (70 to 80%) and wood (60 to 70%), the 35S was predominantly found in the HCl soluble fraction. However, 35S-cysteine, the compound fed to the leaves was not exported out of the fed leaf. Along the trunk 35S-cysteine was neither determined in bark nor in wood sections. The only low molecular mass S-compounds found was 35S-glutathione (GSH). The 35S-sulphate detected in bark and wood origined from cysteine oxidation in the leaf tissue and from contamination of the 35S-cysteine feeding solution. The ratio of GSH to sulphate decreased with increasing distance from the fed leaf. Apparently, 35S-radioactivity was transported as sulphate and GSH in the phloem in basipetal direction, but GSH was removed preferentially out of the phloem along the transport path. 35S-radioactivity exported out of the phloem and transported into the wood of the trunk was not retranslocated in the xylem. It may therefore be assumed that part of the 35S translocated was stored in ray cells, medullary sheath cells and/or pith parenchyma cells. Girdling experiments in which the bark of the trunk was peeled off basipetal to the branch containing the fed leaf support these assumptions.
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