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  • 1
    Electronic Resource
    Electronic Resource
    Simulation of marked root hair curling in Rhizobium-legume symbiosis (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 59 (1983), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The soil bacterium Rhizobium infects its leguminous host plants in temperate regions of the world mostly by way of the growing root hairs. Root hair curling is a prerequisite for root hair infection, although sidelong root hair infections occasionally have been observed. The processes underlying Rhizobium-induced root hair curling are unknown.Computer simulation of root hair growth indicates that one-sided tip growth inhibition by Rhizobium can result in root hair curling when three conditions are simultaneously fulfilled: 1) rhizobial growth inhibition is strong enough to prevent removal out of the tip growth range: 2) root hair surface growth between the attached Rhizobium and the root hair top is inhibited; 3) rhizobial growth inhibition is limited to one side of the root hair.The results predict that root hair curling by stimulation of tip growth is improbable. This study accentuates the need for information about the growth processes contributing to tip growth in leguminous root hairs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1983.tb04216.x
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  • 2
    Electronic Resource
    Electronic Resource
    A non-invasive method for the routine-estimation of fresh weight of cells grown in batch suspension cultures (1992)
    Springer
    Plant cell reports 11 (1992), S. 146-149 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A simple apparatus was designed to allow sedimentation of plant cells grown in batch suspensions in Erlenmeyer flasks. After sedimentation the height of the cell mass along the glass wall was measured with a ruler fixed in the apparatus. The cell volume after sedimentation, calculated from this height, appeared highly correlated with the fresh weight of cells. This result was found with eight cell lines in two Laboratories. The method proved to be very suitable to allow routinely measurement of FW without the destruction of cells, from many samples, in a short time, during each phase of the growth cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232168
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  • 3
    Electronic Resource
    Electronic Resource
    Initial proliferation of cortical cells in the formation of root nodules in Pisum sativum L. (1973)
    Springer
    Planta 114 (1973), S. 17-28 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Root nodule initiation in Pisum sativum begins with cell divisions in the inner cortex at some distance from the advancing infection thread. After penetrating almost the entire cortex, the branches of the thread infiltrate the meristematic area previously initiated in the inner cortical cells. These cells are soon invaded by bacteria released from the infection thread and subsequently differentiate into non-dividing, bacteriod-containing cells. As the initial meristematic centre in the inner cortex is thus lost to bacteroid formation, new meristematic activity is initiated in neighbouring cortical cells. As development proceeds, more cortical layers contribute to the nodule, with the peripheral layer and apical meristem of the nodule not invaded by bacteria. Lateral root primordia are initiated in a region separate from that in which nodules are formed, with the lateral primordia being closer to the root apex. This is interpreted to indicate that the physiological basis for nodule initiation is distinct from that for initiation of lateral roots. The role of a single tetraploid cell in nodule initiation is refuted, as is the existence of incipient meristematic foci in the root. It is suggested that the tetraploid cells in nodule meristems arise from pre-existing endoreduplicated cells, or by the induction of endoreduplication in diploid cortical cells by Rhizobium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390281
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  • 4
    Electronic Resource
    Electronic Resource
    The role of hormones and gradients in the initiation of cortex proliferation and nodule formation in Pisum sativum L. (1973)
    Springer
    Planta 114 (1973), S. 29-39 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of exogenous phytohormones on proliferation of the root cortex, and their relation to the division factors from Rhizobium which participate in the initiation of root nodules, were studied using explants of root-cortex tissue from 7-day-old, sterile pea plants. The explants were cultured for 7 days on a synthetic nutrient medium supplemented with auxin, or auxin and cytokinin. With only auxin present in the medium, ca. 10% of the explants showed cell proliferation. With both auxin and cytokinin this percentage was much higher (ca. 80%). The active explants showed proliferation patterns which were similar to or could be derived from a pattern with three predominant meristematic areas in the inner cortex opposite the three xylem radii of the excised central cylinder. These proliferation patterns were similar to the initial proliferative stages in root-nodule formation in seedling intact roots. From this restricted division response of the explants to the hormones, a hypothesis of endogenous division factors is proposed. To test this hypothesis, extractions of root tissue were performed. The addition of a crude alcoholic extract from the central cylinder or the cortex to the medium resulted in cell divisions throughout the cortex. The results are interpreted as evidence for the presence of a transverse gradient system of (an) unknown cell-division factor(s) in the root cortex which may control the induction of cell divisions in nodule initiation brought about by the release of auxin and cytokinin from Rhizobium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390282
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  • 5
    Electronic Resource
    Electronic Resource
    Modulation of the number of membrane-bound auxin-binding sites during the growth of batch-cultured tobacco cells (1981)
    Springer
    Planta 152 (1981), S. 415-419 
    Details
    ISSN: 1432-2048
    Keywords: Auxin-binding site ; Cell suspension culture ; Growth cycle ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the modulation of the number of membrane-bound naphthaleneacetic acid (NAA)-binding sites during the growth cycle of tobacco cells in batch culture. Both cell number and specific NAA-binding increased exponentially, but at different rates and for different periods. This caused a characteristic modulation of the number of binding sites per cell during the growth cycle: During the first day of the lag phase this number decreased; in the exponential phase it rose markedly, and in the stationary phase it was constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385357
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  • 6
    Electronic Resource
    Electronic Resource
    The complex kinetics of auxin-binding to a particulate fraction from tobacco-pith callus (1983)
    Springer
    Planta 158 (1983), S. 10-15 
    Details
    ISSN: 1432-2048
    Keywords: Auxin binding, sites and kinetics ; Nicotiana (callus), auxin binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The kinetics of binding of 1-naphthylacetic acid to particulate fractions from tobacco-pith callus were studied. This binding site does not bind auxin at 0° C. Binding experiments performed at 25° C demonstrated an apparent K a of approx. 6.5·106 M-1. A filtration method was developed in order to study non-equilibrium kinetics of this binding. Dissociation of the complex of auxin and binding site indicates the presence of at least two binding components with dissociation rate constants (k off) of 6.1·10-3 min-1 and 6.0·10-2 min-1. This binding behaviour was not independent, indicating that the binding of auxin to the particulate fractions was more complex than binding of one hormone molecule to one binding site. This complexity was further confirmed by experiments in which the initial velocity of complex formation was measured. A model was worked out into which our data fit without contradictions. It involves the binding of four hormone molecules to one receptor molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395397
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  • 7
    Electronic Resource
    Electronic Resource
    Auxin-binding by particulate fractions from tobacco leaf protoplasts (1980)
    Springer
    Planta 150 (1980), S. 9-12 
    Details
    ISSN: 1432-2048
    Keywords: Auxin binding ; Nicotiana ; Plasma membrane ; Protoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vitro binding of 1-naphthaleneacetic acid (NAA) to particulate fractions from tobacco leaf protoplasts was studied. In freshly isolated protoplasts no specific binding could be detected, whereas it was present in particulate fractions from tobacco leaves. It is concluded that the NAA-binding-sites are probably located at the external face of the plasma membrane; they are destroyed during protoplast isolation by proteolytic enzymes in the cellulase and macerozyme preparations. After culturing the protoplasts for 3–4 d, the first cell divisions were observed and at the same time specific NAA-binding became detectable. The affinity constant for NAA was approx. 2·106 mol-1 and the number of binding sites increased during further culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385607
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  • 8
    Electronic Resource
    Electronic Resource
    Naphthylphthalamic acid-binding sites in cultured cells from Nicotiana tabacum (1985)
    Springer
    Planta 164 (1985), S. 69-74 
    Details
    ISSN: 1432-2048
    Keywords: Auxin (binding) ; Cell culture (hormone binding) ; Naphthylphthalamic acid ; Nicotiana (auxin binding)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Naphthylphthalamic acid (NPA), an inhibitor of polar auxin transport, binds with high affinity to membrane preparations from callus and cell suspension cultures derived from Nicotiana tabacum (K d approx. 2·10−9 M). The concentration of membrane-bound binding sites is higher in cell suspension than in callus cultures. The binding of NPA to these sites seems to be a simple process, in contrast to the binding of the synthetic auxin naphthylacetic acid (1-NAA) to membrane preparations from callus cultures, which is more complex (A.C. Maan et al., 1983, Planta 158, 10–15). Naphthylacetic acid, a number of structurally related compounds and the auxin-transport inhibitor triiodobenzoic acid were all able to compete with NPA for the same binding site with K d values ranging from 10−6 to 10−4 M. On the other hand, NPA was not able to displace detectable amounts of NAA from the NAA-binding site. A possible explantation is the existence of two different membrane-bound binding sites, one exclusively for auxins and one for NPA as well as auxins, that differ in concentration. The NPA-binding site is probably an auxin carrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391027
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  • 9
    Electronic Resource
    Electronic Resource
    Auxin-induced rapid changes in translatable mRNAs in tobacco cell suspension (1987)
    Springer
    Planta 172 (1987), S. 514-519 
    Details
    ISSN: 1432-2048
    Keywords: Auxin ; Cell division ; mRNA induction ; Nicotiana (cell suspension) ; Translation (in vitro)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When 2,4-dichlorophenoxyacetic acid (2,4-D)-dependent tobacco cell suspensions, one normal and one transformed by Agrobacterium tumefaciens, were subcultured on hormone-lacking medium the stationary phase of the cell cycle was reached earlier than on medium containing 2,4-D. Addition of the auxin 2,4-D could restore cell division activity within 10–12 h for the most rapidly reacting cell line. The cell-division response was characterized as being auxin-specific and optimal with 2,4-D at 2.2 10-6 M. Although the cell lines used showed different characteristics, both reacted with a rapid increase in at least three mRNA species within 1 or 2 h after 2,4-D application. Two, 2,4-D-induced protein spots, seen after in-vitro translation, had the same characteristics (MWs 35 kilodaltons (kDa) and 25 kDa with isoelectric points of 7.1 and 6.3, respectively) in both cell lines. Water-treated controls did not show alterations in the translatable mRNA populations. This indicates that the accumulation of the corresponding mRNAs is an early hormone-induced event. Since cell division is the only measurable reaction found after auxin application, cell systems as described here offer excellent possibilities for studying early auxin-induced changes at the molecular level preceding mitosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393868
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  • 10
    Electronic Resource
    Electronic Resource
    Characterization of a cytoplasmic auxin receptor from tobacco-pith callus (1980)
    Springer
    Planta 149 (1980), S. 44-47 
    Details
    ISSN: 1432-2048
    Keywords: Auxin receptor ; Callus ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cultured tobacco-pith tissue contains a cytoplasmic receptor for indoleacetic acid (IAA). The concentration of binding sites is very low in comparison to that of several auxin receptors found by other investigators. A few obvious possible causes (degradation or inactivation) were investigated. From the results we conclude that the low number of binding sites is real. The receptor binds IAA optimally at pH 7.5–7.8 and at a temperature of 24–30°C, when incubated for 25–30 min. The binding is very specific, as is shown by competition experiments. The concentration of the receptor in the callus tissue changes dramatically during each culture period, which suggests a possible role in development. The receptor was partly purified by gel filtration on Sepharose 6B followed by ion-exchange chromatography on DEAE-cellulose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386225
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