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  • 1
    Electronic Resource
    Electronic Resource
    Proton/chloride cotransport in Chara: mechanism of enhanced influx after rapid external acidification (1985)
    Springer
    Planta 163 (1985), S. 411-418 
    Details
    ISSN: 1432-2048
    Keywords: Chara ; Choride influx ; Cotransport ; pH jump ; Proton motive force
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rapid lowering of the external pH (“pH jump”) enhances Cl− influx in Chara. Experiments were conducted to distinguish between two factors which have previously been proposed to mediate in the response: raised cytoplasmic pH and lowered cytoplasmic Cl− concentration. It is concluded that the latter alternative is more likely because: i) Cl− influx is reduced at high external pH; ii) influx following the pH jump is never greater than that following pretreatment in Cl−-free solution, which reduces cytoplasmic Cl− concentration (“Cl− starvation”); iii) the joint application of pH jump and Cl− starvation does not result in a greater Cl− influx than does Cl− starvation alone; and iv) addition of NH 4 + , which increases cytoplasmic pH, does generate an additional stimulation of Cl− influx following a pH jump. It is suggested that the increased cytoplasmic pH at the end of pretreatment at high external pH decays rapidly during the pH jump, and thus any effect on Cl− influx is so transient as to be undetectable by the methods used. The results are discussed in terms of a reaction kinetic model for 2H+/Cl− cotransport (Sanders, D. and Hansen, U.-P, 1981, J. Member. Biol. 58, 139–153) which describes quantitatively; i) the effects of NH 4 + on Cl− influx in terms involving only a change in cytoplasmic pH; and ii) the combined effects of Cl− starvation and NH 4 + in terms involving only changes in Cl− concentration and cytoplasmic pH. Conversely, the combined effects of Cl− starvation and pH jump cannot be described by the model if the effect of the pH jump is the consequence of increased cytoplasmic pH. The simple interpretation of experiments on whole cells involving manipulation of $$\Delta \bar \mu _{{\text{H}}^ + } $$ (the electrochemical potential difference for protons across the plasma membrane) is questioned in the light of these and previous findings that secondary factors can determine the response of Cl− transport in Chara.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395151
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  • 2
    Electronic Resource
    Electronic Resource
    Measurement of calcium fluxes in plants using 45Ca (1992)
    Springer
    Planta 186 (1992), S. 558-566 
    Details
    ISSN: 1432-2048
    Keywords: Calcium influx ; Cell wall and calcium ; Chara ; Cytoplasmic calcium concentration ; Lanthanum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper deals with the effect of calcium binding in the cell wall on the measured 45Ca influx in Chara corallina Klein ex Will. esk. R.D. Wood. Calcium in the cell wall was in the range 687–1197 (μmol · m−2 compared to the sap which contained only 144–256 μmol · m−2. In dilute culture solutions the calcium content of the cell wall was relatively independent of external calcium at concentrations above about 0.1 mol · m−3. The half-times for exchange of calcium from 45Ca-labelled cell walls varied from 45 min at 0.05 mol · m−3 to less than 2 min at 2 mol · m−3. The effectiveness of other cations in displacing calcium from cell walls was in the order La 〉 Zn 〉 Co 〉 Ni 〉 Mg. Rinsing of 45Ca-labelled cell walls in 2 mol · m−3 LaCl3 for 20 min removed more than 99% of the bound 45Ca. However, the residual 45Ca activity in isolated cell walls following La3+ rinsing was similar to that in whole cells. It is concluded that in whole cells 45Ca influx cannot normally be distinguished from extracellular binding of calcium. Methods are described for the measurement of 45Ca fluxes in charophyte cells by isolation of intracellular 45Ca after the uptake period using techniques which avoid contamination from the large amount of tracer bound in the cell wall. At an external calcium concentration of 1 mol · m−3, the plasmalemma influx was approx. 0.2 nmol · m−2 · s−1 of which about half entered the vacuole and half was effluxed back into the external solution. The cytoplasm filled with calcium with a half-time of 40–50 min with an ‘apparent’ pool size of 50 mmol · m−3. After 2 h the net flux to the cell was almost the same as the vacuolar flux. The fluxes reported are an order of magnitude lower than previously reported calcium fluxes in plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198036
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  • 3
    Electronic Resource
    Electronic Resource
    Calcium/aluminium interactions in the cell wall and plasma membrane of Chara (1995)
    Springer
    Planta 195 (1995), S. 362-368 
    Details
    ISSN: 1432-2048
    Keywords: Aluminium toxicity ; Calcium influx ; Cellwall and calcium ; Chara Lanthanum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The proposal that aluminium (Al) toxicity in plants is caused by either inhibition of Ca2+ influx or by displacement of Ca2+ from the cell wall, was examined. For this study the giant alga Chara corallina Klein ex Will. em. R.D. Wood was selected because it shows a similar sensitivity to Al as in roots of higher plants and, more importantly, it is possible to use the large single internodal cells to make accurate and unambiguous measurements of Ca2+ influx and Ca2+ binding in cell walls. Growth of Chara was inhibited by Al at concentrations comparable to those required to inhibit growth of roots, and with a similar speed of onset and pH dependence. At Al concentrations which inhibited growth, influx of calcium (Ca2+) was only slightly sensitive to Al. The maximum inhibition of Ca2+ influx at 0.1 mol·m−3 Al at pH 4.4 was less than 50%. At the same concentration, lanthanum (La3+) inhibited influx of Ca2+ by 90% but inhibition of growth was similar for both La3+ and Al. Removal of Ca2+ from the external solution did not inhibit growth for more than 8 h whereas inhibition of growth by Al was apparent after only 2.5 h. Ca2+ influx was more sensitive to Al when stimulated by addition of high concentrations of potassium (K+) or by action potentials generated by electrical stimulation. Other membrane-related activities such as sodium influx, rubidium influx and membrane potential difference and conductance, were not strongly affected by Al even at high concentrations. In isolated cell walls equilibrated in 0.5 mol·m−3 Ca2+ at pH 4.4, 0.1 mol·m−3 Al displaced more than 80% of the bound Ca2+ with a half-time of 25 min. From the poor correlation between inhibition of growth and reduction in Ca2+ influx, it was concluded that Al toxicity was not caused by limitation of the Ca2+ supply. Short-term changes in other membrane-related activities induced by Al also appeared to be too small to explain the toxicity. However the strong displacement, and probable replacement, of cell wall ca2+ by Al may be sufficient to disrupt normal cell development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202593
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  • 4
    Electronic Resource
    Electronic Resource
    The uptake and metabolism of urea by Chara australis: IV. Symport with sodium—A slip model for the high and low affinity systems (1993)
    Springer
    The journal of membrane biology 136 (1993), S. 263-271 
    Details
    ISSN: 1432-1424
    Keywords: Sodium ; Urea ; Symport ; Cotransport ; Charophytes ; Slip model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We have previously investigated the electrogenic influx of urea in Chara, and the urea- and sodium-dependent membrane current. We have shown that there is a sodium-stimulated component of urea influx and a urea-stimulated component of sodium influx, and that these are of the same size. We conclude that the electrogenic inward transport of urea, and of its analogues acetamide and acrylamide, is by sodium symport, with a stoichiometric ratio of 1∶1. The kinetics of the fluxes and currents show two different K M values for sodium in different cells and two different kinds of kinetics for the effect of urea on membrane current, one of which fits the Michaelis-Menten equation, while the other shows a maximum and fits the difference of two Michaelis-Menten terms, suggesting a phenomenon like cis-inhibition. Similarities in kinetic characteristics between the inhibitory site and the electrically silent uptake site (System II) lead us to suggest that the same protein may be responsible for both the low-K M, electrogenic influx of urea (System I) and the high-K M, electrically silent influx by System II. We suggest a “slip” model for urea uptake in Chara.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233665
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  • 5
    Electronic Resource
    Electronic Resource
    Inheritance of foreign genes in transgenic bean (Phaseolus vulgaris L.) co-transformed via particle bombardment (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 142-150 
    Details
    ISSN: 1432-2242
    Keywords: Transgenic bean ; Phaseolus vulgaris ; Co-transformation ; Biolistic ; Inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Exploiting the biolistic process we have generated stable transgenic bean (Phaseolus vulgaris L.) plants with unlinked and linked foreign genes. Co-transformation was conducted using plasmid constructions containing a fusion of the gus and neo genes, which were co-introduced with the methionine-rich 2S albumin gene isolated from the Brazil nut and the antisense sequence of AC1, AC2, AC3 and BC1 genes from the bean golden mosaic geminivirus. The results revealed a co-transformation frequency ranging from 40% to 50% when using unlinked genes and 100% for linked genes. The introduced foreign genes were inherited in a Mendelian fashion in most of the transgenic bean lines. PCR and Southern blot hybridization confirmed the integration of the foreign genes in the plant genome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225739
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  • 6
    Electronic Resource
    Electronic Resource
    Inheritance of foreign genes in transgenic bean (Phaseolus vulgaris L.) co-transformed via particle bombardment (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 142-150 
    Details
    ISSN: 1432-2242
    Keywords: Key words Transgenic bean ; Phaseolus vulgaris ; Co-transformation ; Biolistic ; Inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Exploiting the biolistic process we have generated stable transgenic bean (Phaseolus vulgaris L.) plants with unlinked and linked foreign genes. Co-transformation was conducted using plasmid constructions containing a fusion of the gus and neo genes, which were co-introduced with the methionine-rich 2S albumin gene isolated from the Brazil nut and the antisense sequence of AC1, AC2, AC3 and BC1 genes from the bean golden mosaic geminivirus. The results revealed a co-transformation frequency ranging from 40% to 50% when using unlinked genes and 100% for linked genes. The introduced foreign genes were inherited in a Mendelian fashion in most of the transgenic bean lines. PCR and Southern blot hybridization confirmed the integration of the foreign genes in the plant genome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050259
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    Paper (German National Licenses)
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