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  • 1
    ISSN: 1432-2048
    Keywords: Calvin cycle ; Chlorophyll fluorescence ; Helianthus (photosynthesis) ; Light scattering ; Photosynthesis (inhibition)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthesis of Helianthus annuus L. leaves was transiently inhibited and respiration was stimulated when a leaf was detached from the plant by cutting the petiole under water. These effects were caused by a solute which was released by cutting and was transported by the transpiration stream to the leaf blade. This endogenous solute decreased the quantum efficiency of photosynthesis and inhibited reactions of the Calvin cycle. It exerts its effects by uncoupling ATP synthesis from electron transport, thus stimulating respiration and inhibiting photosynthesis. The observation that not only the ATP-dependent reactions of photosynthesis, but also the light-regulated enzymes such as fructose bisphosphatase and ribulose bisphosphate carboxylase were inhibited in the presence of the solute illustrates the complex dependence of Calvin-cycle enzymes on the energization and the redox state of the thylakoid system. Since electron pressure increased during the inhibition of photosynthesis, deactivation of fructose bisphosphatase cannot be explained by effects on the thioredoxin system which is responsible for the light activation of this enzyme.
    Type of Medium: Electronic Resource
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  • 2
    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.
    Type of Medium: Electronic Resource
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