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  • 1
    Unknown
    Weinheim : VCH
    Type of Medium: Unknown
    Pages: 577 S.
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  • 2
    Book
    Berlin : Springer
    Type of Medium: Book
    Pages: xvi, 373 Seiten , Illustrationen, Diagramme
    ISBN: 9783662529829
    URL: 01
    URL: 04
    Language: German
    Note: Dieses Buch weckt Begeisterung für die faszinierende Welt der Pflanzen. Pflanzen sind ganzheitliche Organismen. Sie verarbeiten Reize zu Information. Sie haben eine Uhr und ein Gedächtnis. Sie vollbringen unermessliche Dienstleistungen für unser Leben auf dieser Erde. Durch die Photosynthese liefern sie die Grundlage für die Ernährung allen Lebens. Sie gestalten unsere Umwelt und Lebensräume. Um das zu zeigen, befasst sich dieses Buch besonders mit den Höheren Pflanzen und ihrer Eroberung des Festlandes. Pflanzen bergen Schönheit und regen unser ästhetisches Empfingen an. Zielgruppe sind sowohl interessierte Laien wie auch ein Fachpublikum, da das Buch einerseits verständlich wie ein Sachbuch geschrieben ist, andererseits aber auch den Anspruch hat, eingehendes, fachliches Wissen zu vermitteln. Die Verknüpfung eines verständlichen Schreibstils mit wissenschaftlicher Tiefe hat auf dem Markt der angebotenen Bücher zur Botanik einen Alleinstellungswert.
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  • 3
    Unknown
    Weinheim : Wiley-VCH
    Type of Medium: Unknown
    Pages: 625 S. + CD-ROM
    Edition: 4., verbesserte Auflage
    ISBN: 3527306234
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  • 4
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Centrifugation techniques are described which allow that glass microelectrodes can be inserted separately into cytoplasm and vacuoles of intact cells of the mossMnium cuspidatum. This provides unequivocal measurements of the plasmalemma potential (E co between cytoplasm and outer medium). For various reasons, which are discussed in detail, determinations of the tonoplast potential (E vc between vacuole and cytoplasm) remain ambiguous. In the moss cells equilibrated with artificial pond water (APW),E co is highly negative (i.e. −130 to −190 mV).E vc is either close to 0 mV or positive (+60 to +65 mV) depending on the interpretation of the measurements. However, there is no reason to suggest that under these conditions highly negative potentials occur at the tonoplast.
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  • 5
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The uptake of35S-labelled sulfate ions into hydropote cells (densely cytoplasmic gland cells) and into epidermal cells (highly vacuolated cells) ofNymphaea leaves is dependent on metabolic energy. Only a very small fraction of the accumulated35S is incorporated into organic macromolecules during the experimental period. Both cell types exhibit a hyperbolic isotherm for35S uptake from labelled K2SO4 solutions over an external concentration range of 0 to 0.5mm. Although the gland and epidermal cells behave qualitatively similarly, the glands generally absorb about twice as much35S per unit area of sections of the cells as do the epidermal cells. At 3 °C, poly-l-lysine concentrations of 10−8 m and up to 10−7 m enhance35S uptake by the epidermal and gland cells for the first 7.5 hr after application of the poly-l-lysine. Samples treated with 5×10−7 m poly-l-lysine are indistinguishable from the controls over the same period. After longer periods of treatment with poly-l-lysine (7.5 to 24 hr), the rates of35S uptake were reduced by all poly-l-lysine concentrations between the range 10−8 to 5×10−7 m. After 7.5 hr of35S uptake, the control samples contained the smallest amount of label, but after an uptake period of 24 hr the amount of label in the controls is considerably larger than in samples treated with poly-l-lysine. The results suggest that poly-l-lysine increases the membrane permeability and alters the metabolic uptake of sulfate in both hydropotes and epidermal cells.
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  • 6
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The membrane potential of cells in leaf slices of the CAM plantKalanchoë daigremontiana Hamet et Perrier in the light and in the dark is −200 mV on the average; it is reversibly depolarized by the metabolic inhibitors FCCP (5×10−6 m) and CN− (5×10−3 m); it shows the light-dependent transient oscillations ubiquitously observed in green cells; it is independent of the amount of malic acid accumulated in the cells (in a tested range between 30 and 140mm); and it is considerably hyperpolarized by the fungal toxin fusicoccin (30×10−6 m). Fusicoccin inhibits nocturnal malic acid accumulation in intact isolated phyllodia of the CAM plantKalanchoë tubiflora (Harv.) Hamet but does not affect remobilization of malic acid during the day. Electrochemical gradients for the various ions resulting from dissociation of malic acid, i.e., H+, Hmal− and mal2−, were calculated using the Nernst equation. With a very wide range of assumptions on cytoplasmic pH and malate concentration results of calculations suggest uphill transport of H+ and Hmal− from the cytoplasm into the vacuole, while mal2− might be passively distributed at the tonoplast. On the basis of the present data the most likely mechanism of active malic acid accumulation in the vacuoles of CAM plants appears to be an active H+ transport at the tonoplast coupled with passive movement of mal2− possibly mediated by a translocator (“catalyzed diffusion”), with subsequent formation of Hmal− (2 H++mal2−→H++Hmal−) at vacuolar pH's.
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  • 7
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The coupling of ion transport to energy sources in the light and in the dark in green cells ofAtriplex spongiosa leaves was investigated using light of different qualities, an inhibitor of electron transport (dichlorophenyl dimethyl urea), and an uncoupler (p-CF3O-carbonyl cyanide phenylhydrazone). Two different mechanisms of ion uptake were, distinguished. (1) A light-dependent Cl− pump which is linked to light-dependent K+ uptake. The energy for this pump is probably derived from photosynthetic electron transport or from nicotinamide adenine dinucleotide phosphate, reduced form. This mechanism is dichlorophenyl dimethyl urea-sensitive and enhanced by uncouplers. (2) A mechanism independent of light, which operates at the same rate in the light and in the dark. This mechanism is sensitive to uncouplers. It is probably aK−Na exchange mechanism since K+ and Cl− uptake and a small net uptake of H+ are balanced by Na+ loss.
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  • 8
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Transcellular electrical profiles ofKalanchoë leaf cells were obtained by pushing a glass micro-saltbridge through cells with the tip consecutively in the cell wall, cytoplasm, and vacuole. The electrical resistance of the cell wall was too small to be detectable, that of the plasmalemma and tonoplast was about 0.18–0.21 and 0.16–0.18 Ωm2, respectively. The electrical potential difference between the cytoplasm and the external medium,ψ co , was ≈−180 mV, the potential difference between the vacuole and the medium,ψ vo , was ≈−155mV, and thus the mean potential difference at the tonoplast,ψ vc , was about +25 mV. Potential difference,ψ vo , was independent of proton concentration in the external medium between pH 9 and 5.5, and behaved like an H+-electrode between pH 5 and 3. Depolarizations and hyperpolarizations ofψ vo obtained by increasing and decreasing, respectively, the Na+-concentrations in the medium were smaller than with changing K+-concentrations, suggesting that permeabilities areP Na +/P K +≈-0.23. Assessment of K+-compartmentation by flux analysis gave K+-concentrations in the cytoplasm including chloroplasts (c c) and vacuole (c v) asc c between 200 and 400 mmol kg−1 FrWt andc v ≈-15 mmol kg−1 FrWt. The Nernst criterion suggests that metabolically regulated K+ transport out of the vacuoles concentrates K+ in the cytoplasm. Fusicoccin (10−5 m) hyperpolarizedψ co by about 100 mV and depolarized the positiveψ vc by about 10 mV, the latter presumably being an insignificant effect. The evidence for the existence of proton pumps exchanging H+ and K+ at the plasmalemma and at the tonoplast is discussed.
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  • 9
    ISSN: 1432-1424
    Keywords: crassulacean acid metabolism ; Kalanchoë ; malic acid ; tonoplast ; membrane permeability ; lipid-solution mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary An analysis was carried out of the mechanism of malic-acid efflux from vacuoles of mesophyll cells of the crassulacean acid metabolism (CAM) plantKalanchoë daigremontiana. Following its accumulation in the vacuole as a result of nocturnal CO2 fixation, the malic acid is passively transported back across the tonoplast in the subsequent light period and is decarboxylated in the cytoplasm. Malic-acid efflux was studied using leaf slices in solution or by following malic-acid utilization (deacidification) in leaves of intact plants. Samples of leaf-cell sap were taken at different times during the day-night rhythm to establish the relation between cell-sap pH and malate content. From the empirically determined pK values for malic acid in the cell sap, it was then possible to calculate the proportion of malate existing as the undissociated acid (H2mal0) and in the anionic forms (Hmal1− and mal2−) for all times during the CAM rhythm. In leaf-slice experiments it has been found that the rate of malic-acid efflux increases exponentially with the malic-acid content of the tissue. This is shown to be related to the increasing amounts of H2mal0 present at high malic-acid contents. At low malic-acid contents (<65 mol m−3), when H2mal0 is not present in significant amounts, efflux must be in the form of Hmal−1 and/or mal2−. At high malic-acid contents it is suggested that efflux occurs predominantly in the form of passive, noncatalyzed diffusion of H2mal0 across the tonoplast by a ‘lipid-solution’ mechanism. This is supported by the fact that the slope of the curve relating efflux to H2mal0 concentration, when corrected for the presumed contributions from Hmal1− and mal2− transport and plotted on a log-log basis, approaches 1.0 at the highest malic-acid contents. Moreover, the permeability coefficient required to be consistent with such a mechanism $$(P_{H_2 mal^0 } = 1.0to2.0 \times 10^{ - 8} m\sec ^{ - 1} )$$ is similar to that estimated from a Collander plot, using the partition coefficient of malic acid between ether and water. We suggest that $$P_{H_2 mal^0 } $$ may be important in determining the maximum amounts of malic acid that can be accumulated during the CAM rhythm.
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  • 10
    ISSN: 0931-1890
    Keywords: Key words Chlorophyll a fluorescence ; Clusia ; Crassulacean acid metabolism (CAM) ; Electron transport rate through photosystem II ; Malate decarboxylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Changes in chlorophyll a fluorescence during the day and diurnal-changes of net CO2-exchange and organic acid contents were determined in two species of the genus Clusia during the dry season in Venezuela. The investigations included plants of the C3/CAM intermediate species Clusia minor and the C3 species C. multiflora growing at exposed and shaded sites. Both species showed a C3 pattern of net CO2-exchange at the exposed site. In the shade under extreme drought stress C. minor showed a weak expression of CAM without CO2-uptake during the afternoon (phase IV of CAM). C. multiflora growing in the shade exhibited a C3-pattern of net CO2-exchange and a small but significant nocturnal accumulation of citrate. Shaded plants of C. minor were able to double their light utilisation for electron transport and to reduce non-photochemical quenching during phase III compared to phase II of CAM. Furthermore, increase of electron transport rate through photosystem II in phase III of CAM is correlated to decarboxylation of malate. At the exposed site C. multiflora was less negatively affected by high PPFD than C. minor. This was shown by a lower reduction of potential electron quantum yield (Fv/Fm) and higher light utilisation of electron transport of C. multiflora compared to C. minor. At the exposed site C. minor did not make use of the CAM option to increase light utilisation of electron transport and to reduce non-photochemical quenching as did the plants growing in the shade.
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