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  • 1
    Electronic Resource
    Electronic Resource
    Induction of crown galls by Agrobacterium tumefaciens (strain C58) reverses assimilate translocation and accumulation in Kalanchoë daigremontiana (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The mechanism of hormone-enhanced solute accumulation was investigated in crown galls of Kalanchoë diagremontiana, induced by Agrobacterium tumefaciens (C58). Electrophysiological, cytological staining, and 14CO2-tracer techniques were used. Intracellular auxin and zeatinriboside concentration increased in tumours by three and five times, respectively, compared with the mesophyll. In contrast, the electrical membrane potential difference, in particular the energy-dependent component across the plasma membrane of tumours was at least 60 mV smaller than that of mesophyll cells. The detection of functional sieve tubes, metabolically active companion cells and also developed xylem vessels correlated well with evidence for reversed, long-distance, 14C-labelled assimilate flow from CAM–performing mesophyll to sugar and potassium-accumulating tumours. The change in hormone production, encoded by the iaaM, iaaH and ipt T-DNA genes, apparently induced functioning vascular bundles and established a strong sink. From a comparison with tobacco suspension cells (SR1 and SR1-C58), the changes in the amino acid pattern in the mesophyll/tumour complex can be attributed to the enzymatic activities incited by the nos encoding gene. Differences in sugar and inorganic ion content were not apparent in the transformed suspension cells, indicating that the increase in extracellular concentration by enhanced phloem unloading may be the crucial factor for the pathological solute accumulation in the tumours.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1992.tb01485.x
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  • 2
    Electronic Resource
    Electronic Resource
    Fusicoccin-induced membrane depolarization, K+ efflux and extracellular alkalinization in leaves of Vigna unguiculata (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 14 (1991), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. In leaves of three different cultivars of cowpeas (Vigna unguiculata), the fungal toxin fusi-coccin (FC) induced a plasmalemma depolarization from -175 to -100mV, a value slightly below the N2-determined diffusion potential in the dark, and to a lesser extent in the light. The depolarization was preceded by the usual initial membrane hyperpolarization (up to 18mV). The membrane depolarization was accompanied by considerable K+ efflux and extracellular alkalinization. Primary and secondary leaves as well as stem tissue of plants, grown under long-day conditions or in the dark responded similarly. Dark O2 uptake in leaves and hypocotyls was stimulated by FC by up to 77 and 87%, respectively. In contrast, FC caused a typical Em hyperpolarization, K+ influx, extracellular acidification and smaller stimulation of respiration (50%) in leaves of other legumes such as mungbean (Vigna radiata), or soybean (Glycine max). Leaves of navy beans (Phaseolus vulgaris) revealed an intermediate response to FC. The unusual effect of FC in Vigna might be related to the production of toxic catabolites during degradation and fermentation of storage products necessary to meet the strong energy requirement of the pm-H+ ATPase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1991.tb00947.x
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  • 3
    Electronic Resource
    Electronic Resource
    Ethylene production and ACC-accumulation in Agrobacterium tumefaciens-induced plant tumours and their impact on tumour and host stem structure and function (1999)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ethylene emission from wild-type Agrobacterium tumefaciens (C58)-induced stem tumours of Ricinus communis was continuously measured with two different methods, process gas chromatography and photo-acoustic spectrometry. Ethylene production was as high as 700 pmol g FW–1 h–1, namely 140 times greater than emitted by non-tumourized control stems. It was highest in 5-week-old tumours, independent of light, depressed by anoxia and, during water deficit it was stimulated by rewatering. A remarkable concomitant CO-production was discovered. Accumulation of 1-aminocyclopropane-1-carboxylic acid (ACC), the substrate of ACC-oxidase, preceded ethylene emission with a maximum 2 weeks after tumour induction. Simultaneously, the xylem in the tumour-adjacent host stem underwent drastic changes: it increased two to three times in thickness, vessel diameters decreased, the rays remained unlignified and became multiseriate. With increasing emission of ethylene aerenchyma developed in the non-transformed, tumour-surrounding tissue that formerly was stem cortex. Cotyledons reacted with epinastic symptoms indicating induction of senescence. The present results reveal an important role of ethylene, in addition to cytokinin and auxin, for the differentiation and physiology of A. tumefaciens-induced tumours.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00488.x
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  • 4
    Electronic Resource
    Electronic Resource
    Ion fluxes and pH changes induced by trans-plasmalemma electron transfer and fusicoccin in Lemna gibba L. (strain G1) (1990)
    Springer
    Planta 180 (1990), S. 390-399 
    Details
    ISSN: 1432-2048
    Keywords: Charge compensation (plasmalemma) ; Electron transfer (uncoupled) ; Fusicoccin ; Ion flux ; Lemna ; pH Regulation ; Plasmalemma (electrontransfer)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During the reduction of extracellular [Fe(CN)6]3− at the plasmalemma of intact, K+-starved Lemna gibba L. fronds, the external medium was acidified and K+ released, in the absence of inhibitors with rates of 10 e−/8.5 H+/1.5 K+ (μmol·(g FW)−1·−1). In K+ plants the larger K+ efflux caused a lag phase in extracellular acidification and a change in rates to 10 e−/6 H+/4 K+ and in the presence of CN−+salicylhydroxamic acid at pH 5 to 5.2 e−/0 H+/6.6 K+. The e− transfer was accompanied by a membrane depolarization of up to 100 mV and a cytosolic acidification of about 0.6 pH units, but only in K+ plants, where the extracellular acidification was smaller. These results indicate that a stimulation of the plasmalemma H+-ATPase may be triggered either by a cytosolic acidification or by a strong membrane depolarization. It is concluded that the redox system catalyses only uncoupled e− transfer without H+ transfer across the plasmalemma. The obligatory, but secondary charge compensation is partially achieved by the rapid K+ release upon membrane depolarization and partially by the activity of the plasma membrane H+-ATPase, but not by an e−/anion exchange. The extracellular acidification during [Fe(CN)6]3− reduction is generated by the conversion of a strong trivalent into a strong tetravalent anion. This acidification is caused by changes in the concentration ratio of strong cations to strong anions. Efflux of K+ and not the production of organic acids or NAD(P)H oxidation is the chemical cause of the measurable cytosolic acidification. Extracellular acidification was inversely correlated with intracellular acidification. Similarly, fusicoccin-induced pH changes were correlated with changes in the strong-ion concentration difference. Extracellular ± FC-dependent acidification and intracellular alkalinization of up to 0.6 pH units were strongly dependent on K+ fluxes. The ferricyanide-triggered trans-plasmalemma electron-transfer system is an example of how measurable pH changes are the consequence and not the cause of charge-transfer-induced changes in strong-ion fluxes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198791
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  • 5
    Electronic Resource
    Electronic Resource
    Ion fluxes and pH changes induced by trans-plasmalemma electron transfer and fusicoccin inLemna gibba L. (strain G1) (1990)
    Springer
    Planta 180 (1990), S. 390-399 
    Details
    ISSN: 1432-2048
    Keywords: Charge compensation (plasmalemma) ; Electron transfer (uncoupled) ; Fusicoccin ; Ion flux ; Lemna ; pH Regulation ; Plasmalemma (electrontransfer)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During the reduction of extracellular [Fe(CN)6]3− at the plasmalemma of intact, K+-starvedLemna gibba L. fronds, the external medium was acidified and K+ released, in the absence of inhibitors with rates of 10 e−/8.5 H+/1.5 K+ (μmol·(g FW)−1·−1). In K+ plants the larger K+ efflux caused a lag phase in extracellular acidification and a change in rates to 10 e−/6 H+/4 K+ and in the presence of CN−+salicylhydroxamic acid at pH 5 to 5.2 e−/0 H+/6.6 K+. The e− transfer was accompanied by a membrane depolarization of up to 100 mV and a cytosolic acidification of about 0.6 pH units, but only in K+ plants, where the extracellular acidification was smaller. These results indicate that a stimulation of the plasmalemma H+-ATPase may be triggered either by a cytosolic acidification or by a strong membrane depolarization. It is concluded that the redox system catalyses only uncoupled e− transfer without H+ transfer across the plasmalemma. The obligatory, but secondary charge compensation is partially achieved by the rapid K+ release upon membrane depolarization and partially by the activity of the plasma membrane H+-ATPase, but not by an e−/anion exchange. The extracellular acidification during [Fe(CN)6]3− reduction is generated by the conversion of a strong trivalent into a strong tetravalent anion. This acidification is caused by changes in the concentration ratio of strong cations to strong anions. Efflux of K+ and not the production of organic acids or NAD(P)H oxidation is the chemical cause of the measurable cytosolic acidification. Extracellular acidification was inversely correlated with intracellular acidification. Similarly, fusicoccin-induced pH changes were correlated with changes in the strong-ion concentration difference. Extracellular ± FC-dependent acidification and intracellular alkalinization of up to 0.6 pH units were strongly dependent on K+ fluxes. The ferricyanide-triggered trans-plasmalemma electron-transfer system is an example of how measurable pH changes are the consequence and not the cause of charge-transfer-induced changes in strong-ion fluxes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160395
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