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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 1150 (1993), S. 165-172 
    ISSN: 0005-2736
    Keywords: Abscisic acid ; Lipid monolayer ; Liquid-condensed state ; Liquid-expanded state ; Phase transition ; Surface pressure
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Keywords: Abscisic acid ; Chaparral ; Ceanothus thyrsiflorus ; Conductance ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Small shrubs ofCeanothus thyrsiflorus were grown in 19-1 pots irrigated under natural conditions in a chaparral region of Southern California and then subjected to soil drying. Characteristics of leaf gas exchange, leaf water potential, and concentrations of the stress hormone abscisic acid in the xylem sap, ABAxyl, were determined at various stages of drought. Diurnal changes in conductance were strongly correlated with leaf net photosynthesis rate, which provides an effective, integrative predictor of above-ground climate effects on conductance. In drought conditions, ABAxyl concentration increased. Increases in the concentration range of 50–500 nmol/l appeared to induce stomatal closure, restricting water loss and carbon dioxide uptake. When the momentary water potential is related to ABAxyl, ABA appeared to increase significantly only after a threshold of approximately −1.5 MPa was exceeded. At less negative water potentials, large variation in ABAxyl in the 50–1000 nmol/l range occurred for all water-potential values, because ABAxyl remains relatively constant over diurnal courses as water potentials decrease and then recover. When the water potential became more negative than −1.5 MPa, ABAxyl concentrations occurred between approximately 500 and 10 000 nmol/l and even greater in isolated cases. An approximately linear relationship is recognizable between ABAxyl and momentary water potential in this range because in plants under drought conditions, ABAxyl increases during the course of the day as water potential decreases. Increases in ABAxyl in the high concentration range were associated with relatively minor additional restrictions in gas exchange, but they might contribute to improved water use efficiency and explain diurnal changes in the potential for stomatal opening that have been observed in Mediterranean sclerophyllous species. When we examined long-term seasonal change in the response of irrigated plants, changes in average daily temperature greater than 10°C occurred (also associated with shifts in relative humidity and radiation input), which apparently led to small changes in predawn water potential in the −0.1 to −0.7 MPa range. Increases in ABAxyl occurred that were in turn negatively correlated with daily maximum leaf conductance. Thus, chaparral shrubs under non-drought conditions seem to sense even small changes in environmental conditions, in our opinion most probably due to initial drying of the uppermost soil and synthesis of ABA in the shallow roots. The results support the hypothesis that information of photosynthesis rate and predawn water potential may be used as primary variables to predict canopy conductance of Mediterranean sclerophyll shrub vegetation.
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  • 3
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Desiccation tolerance ; Desiccation-related proteins ; Exormotheca ; Marchantiales
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Abscisic acid (ABA) induces formation of a set of proteins in the xerophilic liverwortExormotheca holstii. Some of them have immunological properties similar to the dehydrins of desiccated corn embryos and the desiccation-related proteins ofCraterostigma plantagineum. The fluctuations of endogenous ABA during cycles of desiccation and rehydration seem to be sufficiently high to indicate a role for ABA as a stress hormone and there by as an endogenous inductor of stress-related protein synthesis. Desiccation tolerance disappears when thalli are cultivated for a longer period under well-watered conditions; such thalli are not able to increase stress-dependent ABA biosynthesis sufficiently, or to form the desiccation-related proteins unless they are treated with external ABA. The rehydrated thalli cannot recover from a rapid water loss, while ABA-treated, non-hardened thalli regain their photosynthetic activity within two hours.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Drought tolerance ; Protein synthesis ; Riccia ; Vacuole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The conversion of the submerged form ofRiccia fluitans to the landform either by transfer to a moist solid surface or by treatment with abscisic acid (ABA), is accompanied by the formation of a set of new polypeptides and concomitant down-regulation of other polypeptides. Changes in gene expression were analyzed by twodimensional separations of proteins and differential screening of a cDNA library. One of the landform-specific proteins might depend on the expression of the newly discoveredRic 1 gene. The deduced amino acid sequence of the isolatedRic 1 cDNA clone codes for a protein with a molecular mass of 30.1 kDa. This polypeptide possesses two amino acid sequences which are repeated five times each and it is largely hydrophilic with the exception of a hydrophobic carboxyl-terminal region. Under ABA treatment the expression of theRic 1 mRNA had already reached its maximum after 1 h of incubation. Transferring submerged thalli onto an agar surface resulted in a slower induction. TheRic 1 gene product shows homology to an embryo-specific polypeptide of carrot seeds and to the group 3 of late-embryogenesis-abundant (LEA) proteins. Interestingly, ABA treatment improved the desiccation tolerance of the submerged thalli. Additionally, ABA stimulated the synthesis of a protein which is immunologically related to a tonoplast protein. This finding, together with the fact that the ABA-induced landform exhibits an increased activity of several vacuolar enzymes, may indicate a special role of the tonoplast and the vacuole during ABA-induced conversion of the thallus from the submerged to the terrestrial form.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Planta 134 (1977), S. 295-299 
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Apical dominance ; Auxin ; Gibberellin ; Hormone transport ; Phaseolus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Abscisic acid (ABA) in lanolin, applied to the internode of decapitated runner bean plants enhances the outgrowth of lateral buds. The optimum concentration of the paste is 10-5 M. The effect of ABA is counteracted by indoleacetic acid (IAA) but not by gibberellic acid (GA3). There is no effect when ABA is applied to the apical bud or lateral buds of intact plants. However, 13.2 ng given to the lateral buds of decapitated plants stimulate their growth, whereas higher concentrations are inhibitory. Consequently, ABA enhances growth of lateral buds directly, but only when apical dominance is already weakened. The growth of the decapitated 2nd internode was not affected by ABA. Radioactivity from [2-14C] ABA, applied to nonelongating 2nd internode stumps of decapitated runner bean plants moves to the lateral buds, whereas [1-14C]IAA-and [3H]GA1-translocation is much weaker. ABA transport is inhibited if IAA or [3H]GA1 is applied simultaneously. In elongating internodes [14C]ABA is almost completely immobile. [14C]IAA-and [3H]GA1-translocation is not affected by ABA. The amount of radioactivity from labelled ABA, translocated to the lateral buds, is highest during the early stages of bud outgrowth.
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  • 6
    ISSN: 1432-2048
    Keywords: Abscisic acid ; Auxin ; Glucose-transport ; Glycine-transport ; Lemna ; Membrane potential ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The membrane potential of Lemna gibba G1 was measured with a microelectrode; glucose and glycine uptake were measured with 14C-labeled substances. The membrane potential was increased by 85 mV on the average, after the plants had been pretreated with 10 μM abscisic acid (ABA) for more than 30 min. This effect is not linked to the endogenous level of soluble sugars. The concentration of these soluble sugars was increased to more than 200% by pretreatment of the plants with ABA, however, the respiration of the plants was not affected. ABA stimulated uptake of glucose and glycine. Glucose- and glycine-dependent depolarization and repolarization of the membrane was altered: depolarization was less and repolarization was slower; during uptake of glycine, the first typical phase of repolarization was suppressed. The data suggest that ABA interferes with the primary steps of substrate uptake.
    Type of Medium: Electronic Resource
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