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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 80 (1974), S. 401-405 
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In a study of membrane potential properties of giant cells induced in the roots ofImpatiens balsamina by a rootknot nematode, trains of action potential-like fluctuations were recorded. Giant cells are multinucleate transfer cells, and it is suggested that the occurrence of action potentials may be characteristic of transfer cells.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 87 (1976), S. 273-279 
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The morphology of wall ingrowths in xylem and phloem transfer cells inHelianthemum is different. It is possible to use nematode infection to induce the formation of giant cells which abut both xylem and phloem elements to test whether ingrowth morphology is controlled by the solutes presumed to be transported across the plasmalemma of the cells. This experiment has been done and it is found that although wall ingrowths develop against both xylem and phloem, the giant cells exhibit only the ingrowth structure characteristic of xylem transfer cells.
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  • 3
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The occurrence and position of wall protuberances in giant cells induced in coleus roots by the root-knot nematodeMeloidogyne arenaria is described, and the structure and function of giant cells is compared with that of syncytia induced by cyst-nematodes. Extensive protuberance development occurs on walls of giant cells adjacent to xylem vessels. Protuberances are less well developed next to sieve elements, and almost absent next to parenchyma cells. On walls between giant cells they occur on both sides or only one side. The formation of protuberances indicates that giant cells are multinucleate transfer cells. The position of protuberances marks the wall area where solutes enter the cell. Solutes are obtained from xylem and phloem elements, and the position of protuberances at the junction between giant cells and vascular elements indicates an extensive flow of solutes along cell walls. The observations support the hypothesis that wall protuberances form as a result of selective solute flow across the plasmalemma. No cell wall dissolution was observed, although wall gaps may occur between giant cells as a result of breakage during rapid cell expansion.
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  • 4
    ISSN: 1573-5044
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 12 (1969), S. 469-470 
    ISSN: 1570-7458
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 6
    ISSN: 1572-879X
    Keywords: oscillation ; CO + H2 cooxidation ; chemical sensor ; pellistor ; platinum ; platinum/alumina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Oscillation behaviour of the oxidation of CO (0.2–2.2%) in air over Pt wire coils and over Pt/Al2O3 catalysts deposited onto the coils (pellistors) has been investigated. The waveforms differ considerably between the two catalytic systems. Over unsupported Pt at 240–260° C, regular oscillations were accompanied by slowly declining activity and by deposition of carbon. Over supported Pt at 110–180°C, relatively complex but sustained oscillation occurred by a different mechanism. This oscillation was greatly enhanced by H2 (0.25–1.0%), and may involve fluctuations in the concentrations of CO and H2 around the supported catalyst.
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  • 7
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A comparison of transmembrane potential (pd) properties of parenchyma cells and giant transfer cells induced by a root-knot nematode in the roots ofImpatiens balsamina has been made. Apart from some differences in rate of response to a few treatments, parenchyma and giant cells had similar pd values; active and passive components of the pd (cyanide, azide); responses to total ion concentration, pH and potassium concentration; responses to protein synthesis inhibitors (puromycin, cycloheximide and actinomycin D) and responses to sugars. Both parenchyma cells and giant cells are depolarized by puromycin, cycloheximide and actinomycin D. The cells recover from the depolarization in the presence of cycloheximide, suggesting that this presumed protein synthesis inhibitor does not act in a straight-forward manner. The cells do not recover in the presence of puromycin or actinomycin D. Parenchyma cells and giant cells clearly have different metabolic rates and ion fluxes, but their pd responses are the same. This suggests that the pd does not reflect metabolic activity or ion fluxes of a cell, but is strictly controlled in itself. Part of this control may be via a feedback mechanism acting on an electrogenic pump. The depolarization caused by glucose is induced by aging the cells after excision. The effect is discussed in terms of an H+ dependent cotransport system and an ATPase permease system. The apparent normality of pd responses of nematode-induced giant transfer cells suggests that they may be a useful model system for experiments on higher plant cells.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Planta 165 (1985), S. 205-216 
    ISSN: 1432-2048
    Keywords: Cell division ; Dielectrophoresis ; Electrofusion (electrical parameters) ; Heterokaryon ; Protoplast (mesophyll and suspension) ; Somatic hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The electrical parameters important in the fusion of plant protoplasts aligned dielectrophoretically in high-frequency alternating electric fields have been established. Protoplasts were aligned in an alternating electric field between two relatively distant (1 mm) electrodes, by dielectrophoresis induced by field inhomogeneities caused by the protoplasts themselves. This arrangement allowed ease of manipulations, large throughput and low loss of protoplasts. In analytical experiments, sufficiently large samples could be used to study pulse duration-fusion response relations at different pulse voltages for protoplasts of different species, tissues and size (mesophyll protoplasts of Solanum brevidens, Triticum aestivum, Hordeum vulgare; suspension-culture protoplasts of Nicotiana sylvestris, N. rustica, Datura innoxia and S. brevidens; root-tip protoplasts of Vicia faba, hypocotyl protoplasts of Brassica napus). The percentage of aligned protoplasts that fused increased with increasing pulse parameters (pulse duration; voltage) above a threshold that was dependant on pulse voltage. The maximum fusion values obtained depended on a number of factors including protoplast origin, size and chain length. Leaf mesophyll protoplasts fused much more readily than suspension-culture protoplasts. For both types, there was a correlation of size with fusion yield: large protoplasts tended to fuse more readily than small protoplasts. In short chains (≦five protoplasts), fusion frequency was lower, but the proportion of one-to-one products was greater than in long chains (≧ten protoplasts). In formation by electrofusion of heterokaryons between mesophyll and suspension-culture protoplasts, the fusion-frequency response curves reflected those of homofusion of mesophyll protoplasts rather than suspension-culture protoplasts. There was no apparent limitation to the fusion of the smallest mesophyll protoplast with the largest suspension-culture protoplasts. Based on these observations, it is possible to direct fusion towards a higher frequency of one-to-one (mesophyll/suspension) products by incorporating low densities of mesophyll protoplasts in high densities of suspensionculture protoplasts and by using a short fusion pulse. The viability of fusion products, assessed by staining with fluorescein diacetate, was not impaired by standard fusion conditions. On a preparative scale, heterokaryons (S. brevidens mesophyll-N. sylvestris or D. innoxia suspension-culture) were produced by electrofusion and cultured in liquid or embedded in agar, and were capable of wall formation, division and growth. It is concluded that the electrode arrangement described is more suitable for carrying out directed fusions of plant protoplasts than that employing closer electrodes.
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  • 9
    ISSN: 1432-2048
    Keywords: Abscisic acid and precocious germination ; Embryogenesis ; Hordeum (lectin) ; Lectin ; Triticum (lectin)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Radioimmunoassay has been used to measure levels of wheat-germ agglutinin and barley-germ agglutinin during embryogenesis and germination. The two lectins exhibited similar patterns of accumulation during grain maturation in vivo and both decreased to low levels after imbibition of harvest-ripe grains for 3 d. Precocious germination of immature wheat and barley embryos excised and cultured in vitro could be prevented either by inclusion of abscisic acid or mannitol in the culture medium. Changes in the level of wheat-germ agglutinin induced by in vitro culture depended on the maturation stage of the embryo. No direct correlation was found between application of exogenous abscisic acid and accumulation of the lectin.
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  • 10
    ISSN: 1432-2048
    Keywords: Agrostemma ; Gibberellin ; Growth retardant ; Photoperiodism ; Stem elongation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Agrostemma githago is a long-day rosette plant in which transfer from short days (SD) to long days (LD) results in rapid stem elongation, following a lag phase of 7–8 d. Application of gibberellin A20 (GA20) stimulated stem elongation in plants under SD, while 2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine-carboxylate methyl chloride (AMO-1618, an inhibitor of GA biosynthesis) inhibited stem elongation in plants exposed to LD. This inhibition of stem elongation by AMO-1618 was overcome by simultaneous application of GA20, indicating that GAs play a role in the photoperiodic control of stem elongation in this species. Endogenous GA-like substances were analyzed using reverse-phase high-performance liquid chromatography and the d-5 corn (Zea mays L.) assay. Three zones with GA-like activity were detected and designated, in order of decreasing polarity, as A, B, and C. A transient, 10-fold increase in the activity of zone B occurred after 8–10 LD, coincident with the transition from lag phase to the phase of rapid stem elongation. After 16 LD the activity in this zone had returned to a level similar to that under SD, even though the plants were elongating rapidly by this time. However, when AMO-1618 was applied to plants after 11 LD, there was a rapid reduction in the rate of stem elongation, indicating that continued GA biosynthesis was necessary following the transient increase in activity of zone B, if stem elongation was to continue under LD. It was concluded that control of stem elongation in A. githago involves more than a simple qualitative or quantitative change in the levels of endogenous GAs, and that photoperiodic induction alters both the sensitivity to GAs and the rate of turnover of endogenous GAs.
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