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  • 1
    Electronic Resource
    Electronic Resource
    Growth, membrane potential and endogenous ion currents of willow (Salix viminalis) roots are all affected by abscisic acid and spermine (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 99 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Growth measurements of hormone-treated roots from willow cuttings were combined with electrophysiological recordings to study hormone-induced changes in membrane potential and in endogenous ion currents. The mean growth rate of roots was 10 ± 2 μm min−1 in regular nutrient solution. It increased to 13 ± 2 μm min+1 after application of spermine and decreased to 0.07 ± 0.01 μm min−1 after treatment with abscisic acid (ABA). Transient depolarizations were elicited in root cortex cells by spermine, while ABA caused a transient hyperpolarization. All changes in membrane potential were accompanied by transient responses of the endogenous current. These responses suggest that first anions, then cations leave the root during spermine-induced depolarizations. From the changes of the endogenous current an apparent efflux of anions (presumably Cl−) and cations (presumably K+) of 200 to 700 pmol cm−2 per depolarization was calculated.To further investigate a possible relation between endogenous ion currents, growth and the growth regulators ABA and spermine, long-lasting extracellular vibrating-probe measurements were performed. Control roots showed an inward current of about 1.5 μA cm−2 at the apical elongation zone and an outward current with a maximum density of 1.3 μA cm−2 at the central and basal elongation zone. The addition of ABA and spermine (final concentration 0.1 mM) to the bathing medium affected the endogenous current in opposite ways: ABA caused a reduction of inward and outward current, while spermine stimulated both. Since protons are a major component of the endogenous current, and sucrose can be taken up by root cells from the apoplast via symport with H+, a role of the endogenous current in growth regulation is indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb05353.x
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  • 2
    Electronic Resource
    Electronic Resource
    Evidence for two pathways of phloem loading (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 90 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The minor veins of small leaf discs, punched out of mature leaves and incubated in 14C-sucrose solution, appear labeled in macro- and microautoradiographs. Discs with a labeled vein pattern and with labeled sieve tubes in microautoradiographs were found in Beta vulgaris, Vicia faba, Gomphrena globosa and Antirrhinum majus. However, in several other plant species, minor veins appeared unlabeled in macroautoradiographs when the discs were incubated in 14C-sucrose. Mesophyll cells (Acer pseudoplatanus, Juglans regia, Fagia, sylvatica, Syringa vulgaris, Laburnum anagyroides), bundle-sheath cells of major veins (Salix viminalis, Robinia pseudoacacia, Commelina communis) or epidermal layers (Ginkgo biloba, Chlorophytum comosum) appeared labeled. Lack of radioactivity in sieve tubes of this latter group was confirmed by microauto-radiography. Using 14C-glucose instead of 14C-sucrose, leaf discs of Beta vulgaris showed no labeled vein pattern and in microautoradiographs the sieve tubes appeared unlabeled. In view of the by-pass phloem loading, this study provides evidence for two pathways of phloem loading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb02526.x
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  • 3
    Electronic Resource
    Electronic Resource
    Control of phloem unloading by action potentials in Mimosa (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 83 (1991), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In the sensitive plant, Mimosa pudica, action potentials arise when the leaves are touched and they trigger a sudden decrease in turgor of the pulvinar motor cells, which causes the leaf to close. These potentials may travel through the phloem and they appear to influence pulvinar phloem unloading after stimulation. Mature leaves were exposed to 14CO2 and phloem translocation was observed by autoradiography. In unstimulated pulvini, labeled photoassimilates were restricted to the phloem. However, after stimulation, the 14C-label appeared to be concentrated in the extensor region of the motor cortex. Since stimulation elicits an action potential, it is suggested that it also triggers phloem unloading of sucrose in the pulvini.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb00130.x
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  • 4
    Electronic Resource
    Electronic Resource
    Transport processes in stimulated and non-stimulated leaves of Mimosa pudica (1988)
    Springer
    Trees 2 (1988), S. 7-17 
    Details
    ISSN: 1432-2285
    Keywords: Leaf movements ; Mimosa ; Osmotic mechanisms ; Phloem translocation ; Sucrose unloading ; Turgor release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Mature leaves of Mimosa pudica L. or parts of them were exposed to 14CO2, and translocation was recorded by macroautoradiography. It was observed that considerable amounts of labelled photoassimilates were accumulated in pulvini when the leaf was stimulated. In non-stimulated leaves, no such accumulation of label was observed. Microautoradiographs of pulvinar regions of the non-stimulated leaf showed 14C- label restricted to the phloem. When stimulated, the 14C- label was unloaded from the phloem of the pulvini. Labelled photoassimilates appeared most concentrated in the walls of the collenchymatous cells and beyond in the extensor region of the motor cortex. There, label was accumulated in the apoplastic compartments. Stimulation causes a sudden phloem unloading of sucrose, and its accumulation in the apoplast lowers the water potential which eventually exceeds the osmotic potential of the extensor cells of the motor cortex. By removal of cytoplasmic water the motor cells lose turgidity which results in the closing movement of the leaflets, and — some seconds later — in the bending down of the petiole. In late afternoon night-stimulation triggers sucrose unloading in secondary pulvini. During phases of relaxation, labelled material is taken up by motor cells of the extensor, which concomitantly gain turgor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196974
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  • 5
    Electronic Resource
    Electronic Resource
    Transport processes in stimulated and non-stimulated leaves of Mimosa pudica (1988)
    Springer
    Trees 2 (1988), S. 18-24 
    Details
    ISSN: 1432-2285
    Keywords: Action potential ; Adenine nucleotides ; Aphid stylet ; Mimosa ; Orthophosphate ; Phloem ; Sucrose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Adenosine diphosphate (ADP), adenosine triphosphate (ATP) and orthophosphate were determined in non-stimulated, stimulated and relaxed pulvini of mature Mimosa pudica L. leaves. Additional determinations were made with leaflets, rhachillae, petiole and the stem in the stimulated condition. Results show that the content of adenine nucleotides is approximately twice as high in the pulvini as in the tissues between the pulvini. Orthophosphate, in contrast, occurs at higher concentrations in the connecting tissues than in the pulvini. ATP content is highest in the primary pulvini (0.8 μmol/mg dry wt.) and lowest in the tertiary pulvini. Stimulation causes consumption of ATP with a simultaneous increase in ADP content; however, the response is different in each type of pulvinus. This difference is best expressed in the ATP∶ADP ratio. Stimulation causes the most marked reduction of the ratio (9.5-1.4) in the secondary pulvini which react nyctinastically. Orthophosphate content is reduced by stimulation in all types of pulvini, and is increased during the recovery phase. By using a stylet bundle severed from a feeding aphid by a laser shot as tip for the microelectrode, changes of sieve tube membrane potentials were recorded. The changes of the electropotentials following stimulation show that the sieve tube is the pathway for the transmission of the excitation signal in the form of an action potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196975
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  • 6
    Electronic Resource
    Electronic Resource
    Transport processes in stimulated and non-stimulated leaves ofMimosa pudica (1988)
    Springer
    Trees 2 (1988), S. 7-17 
    Details
    ISSN: 1432-2285
    Keywords: Leaf movements ; Mimosa ; Osmotic mechanisms ; Phloem translocation ; Sucrose unloading ; Turgor release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Mature leaves ofMimosa pudica L. or parts of them were exposed to14CO2, and translocation was recorded by macroautoradiography. It was observed that considerable amounts of labelled photoassimilates were accumulated in pulvini when the leaf was stimulated. In non-stimulated leaves, no such accumulation of label was observed. Microautoradiographs of pulvinar regions of the non-stimulated leaf showed14C- label restricted to the phloem. When stimulated, the14C- label was unloaded from the phloem of the pulvini. Labelled photoassimilates appeared most concentrated in the walls of the collenchymatous cells and beyond in the extensor region of the motor cortex. There, label was accumulated in the apoplastic compartments. Stimulation causes a sudden phloem unloading of sucrose, and its accumulation in the apoplast lowers the water potential which eventually exceeds the osmotic potential of the extensor cells of the motor cortex. By removal of cytoplasmic water the motor cells lose turgidity which results in the closing movement of the leaflets, and — some seconds later — in the bending down of the petiole. In late afternoon night-stimulation triggers sucrose unloading in secondary pulvini. During phases of relaxation, labelled material is taken up by motor cells of the extensor, which concomitantly gain turgor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01196339
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  • 7
    Electronic Resource
    Electronic Resource
    Changes of adenine nucleotide and orthophosphate concentrations in buds of deciduous trees during spring reactivation (1986)
    Springer
    Trees 1 (1986), S. 42-46 
    Details
    ISSN: 1432-2285
    Keywords: Acer ; Adenine nucleotides ; Alnus ; Buds ; Deciduous trees ; Fagus ; Fraxinus ; Orthophosphate ; Quercus ; Reactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Concentrations of AMP, ADP, ATP, and inorganic phosphate (Pi) were determined in buds of five deciduous tree species (Acer pseudoplatanus, Alnus glutinosa, Fagus sylvatica, Fraxinus excelsior, Quercus robur) during spring reactivation from February to the middle of May. In closed buds of diffuse-porous wood trees (Acer, Alnus, Fagus), the content of adenine nucleotides (AdN) increased temporarily between the middle of February and the middle of March. The main increase of AdN concentration appeared either when buds became swollen (Fraxinus, Fagus, Quercus), or at the time of bud-break (Acer, Alnus). Pi content in general decreased during the course of reactivation. It was almost zero in buds of Quercus at bud-break and afterwards, but in Fraxinus Pi concentration rose when bud-break took place. The extremely low AdN content in Quercus buds is contrasted by a steep increase in AdN content in Fraxinus following bud-break. The decrease of AdN content in emerging leaves of Quercus and Fagus could be related to the high age of these trees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197023
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  • 8
    Electronic Resource
    Electronic Resource
    Displacement of frequently occurring heacy metals in autumn leaves of beech (Fagus sylvatica) (1987)
    Springer
    Trees 1 (1987), S. 164-171 
    Details
    ISSN: 1432-2285
    Keywords: Deciduous trees ; Fagus sylvatica ; Autumn leaves ; Iron ; Lead ; Manganese ; Zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary By utilizing energy-dispersive X-ray microanalysis the heavy metals manganese, iron, zinc and lead were determined in different tissues of beech (Fagus sylvatica L.) autumn leaves. It was observed that all four metals were accumulated in sieve element-companion cell complexes of the leaf veins in the period from the green (2 October) to the brown (23 October) leaf coloration. Concomitantly, the concentration of these metals decreased in certain tissues of the stems subtending the leaves. The major reservoirs of heavy metals in the stems were periderm, cortex, pith and xylem rays. Since sieve element-companion cell complexes of the stems showed increasing metal concentrations during the transition from the green to the brown leaf stage, and since this temporary increase also occurred in the petiole phloem, it is inferred that symplastic transport can be used in addition to apoplastic transport for the displacement of heavy metals. It is assumed that the accumulation of heavy metals in the veins of autumn leaves indicates the deposition of surplus ions which are excluded when leaves are cast off.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193559
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  • 9
    Electronic Resource
    Electronic Resource
    Transport processes in stimulated and non-stimulated leaves ofMimosa pudica (1988)
    Springer
    Trees 2 (1988), S. 18-24 
    Details
    ISSN: 1432-2285
    Keywords: Action potential ; Adenine nucleotides ; Aphid stylet ; Mimosa ; Orthophosphate ; Phloem ; Sucrose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Adenosine diphosphate (ADP), adenosine triphosphate (ATP) and orthophosphate were determined in non-stimulated, stimulated and relaxed pulvini of matureMimosa pudica L. leaves. Additional determinations were made with leaflets, rhachillae, petiole and the stem in the stimulated condition. Results show that the content of adenine nucleotides is approximately twice as high in the pulvini as in the tissues between the pulvini. Orthophosphate, in contrast, occurs at higher concentrations in the connecting tissues than in the pulvini. ATP content is highest in the primary pulvini (0.8 μmol/mg dry wt.) and lowest in the tertiary pulvini. Stimulation causes consumption of ATP with a simultaneous increase in ADP content; however, the response is different in each type of pulvinus. This difference is best expressed in the ATP∶ADP ratio. Stimulation causes the most marked reduction of the ratio (9.5-1.4) in the secondary pulvini which react nyctinastically. Orthophosphate content is reduced by stimulation in all types of pulvini, and is increased during the recovery phase. By using a stylet bundle severed from a feeding aphid by a laser shot as tip for the microelectrode, changes of sieve tube membrane potentials were recorded. The changes of the electropotentials following stimulation show that the sieve tube is the pathway for the transmission of the excitation signal in the form of an action potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01196340
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  • 10
    Electronic Resource
    Electronic Resource
    Transport processes in stimulated and non-stimulated leaves of Mimosa pudica (1988)
    Springer
    Trees 2 (1988), S. 65-72 
    Details
    ISSN: 1432-2285
    Keywords: Calcium ; Chlorine ; Ion shifts ; Mimosa pudica ; Potassium ; Seismonastic movements ; X-ray microanalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Using energy-dispersive X-ray microanalysis, the concentrations of ions, especially potassium and chlorine, were determined in different tissues of primary and tertiary pulvini of Mimosa pudica. It was shown that stimulating the leaf was followed by ion displacements which were most striking in the outer extensor cells, resulting in turgor loss. Since Ca concentration remains relatively constant in cell walls of collapsed cells, the changes of K concentration are best described by the K:Ca ratio. After stimulation the K:Ca ratio dropped in the outer extensor of the primary pulvinus from 775.3 to 2.37 in the cytoplasm, and from 542.2 to 9.25 in the cell wall. Changes in chlorine content were less striking in the primary pulvinus. The K∶Cl ratios in some cases were lower than 1.0, which indicates that Cl content can increase, while K content is diminished. In the non-stimulated tertiary pulvini the outer extensor cells show high concentrations of Cl, but much lower Cl concentrations were found after stimulation. In contrast to the primary pulvinus the K content of the tertiary pulvini is very low. In the vascular tissues of both primary and tertiary pulvini stimulation is followed by a release of K and Cl out of the sieve element cytoplasm into the apoplast. K then appears accumulated in the cell walls of the collenchymatous tissue. These displacements lead to the assumption that the collenchymatous apoplast temporarily functions as a reservoir for K and to a lesser extent for Cl. With regard to the mechanism of leaf movement after stimulation, the accumulation of ions in the apoplast seems to be initiated by the decrease of water potential triggered by an apoplastic accumulation of unloaded sucrose (Fromm and Eschrich 1988a). The resulting turgor release in the outer extensor is accompanied by an efflux of ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196751
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