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  • 1
    Electronic Resource
    Electronic Resource
    Characteristics and implications of prolonged fusicoccin-induced growth of Avena coleoptile sections (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: A study has been made of the prolonged growth of Avena coleoptile sections in response to fusicoccin (FC), a phytotoxin that promotes apoplastic acidification. The final amount of FC-induced growth is a function of the FC concentration. Removal of the epidermis speeds up the initial rate of elongation and shortens the duration of the response, without affecting the total amount of extension. A suboptimal FC concentration (7×10−8M) which induces the same rate of proton excretion as does optimal indoleacetic acid (IAA) (1×10−5M), causes elongation which is 60–75% of that induced by IAA in 4 h or 50–65% in 7 h. This suggests that acid-induced extension could make a major contribution to auxin-induced growth for at least 7 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb02520.x
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  • 2
    Electronic Resource
    Electronic Resource
    Protein patterns in the oat coleoptile as influenced by auxin and by protein turnover (1980)
    Springer
    Planta 148 (1980), S. 429-436 
    Details
    ISSN: 1432-2048
    Keywords: Auxin action ; Avena ; Coleoptile ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Synthesis of growth-limiting proteins (GLP) is required for continued auxin-induced elongation of oat (Avena sativa L.) coleoptiles. In order to determine whether GLP synthesis is dependent or independent of auxin, a double-labeling ratio technique, coupled with disc-gel electrophoresis, has been used to assess the effect of auxin on the pattern of protein synthesis. Sections were peeled to enhance amino-acid uptake; proteins were labeled with [14C]- or [3H] leucine in the presence or absence of indole-3-acetic acid for 40 min to 6 h, and were separated into soluble, membrane-associated, and wall-associated fractions. Regardless of the conditions used, or the protein fraction examined, no changes in response to auxin were detected in the pattern of protein synthesis. In order to escape detection by this technique an auxin-induced protein would have to comprise less than 0.75% of the total newly synthesized protein. Thus the synthesis of GLP appears to be independent of auxin. The same technique has been used to follow protein turnover. During the chase, proteins are initially degraded at an average rate of 8% h−1, and some protein bands showed as much as 14% h−1 degradation. No protein was detected which had a turnover rate as rapid as the GLP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02395310
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  • 3
    Electronic Resource
    Electronic Resource
    The Instron technique as a measure of immediate-past wall extensibility (1984)
    Springer
    Planta 160 (1984), S. 514-520 
    Details
    ISSN: 1432-2048
    Keywords: Auxin and wall extensibility ; Avena (wall extensibility) ; Glycine (wall extensibility) ; Instron technique ; Plastic extensibility ; Wall extensibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between the plastic-extensibility values (PEx) obtained in the Instron technique and the growth parameter, wall extensibility (Φ) has been evaluated for Avena sativa L. coleoptile cell walls. The possibility that PEx is proportional to the growth rate rather than to Φ has been eliminated by showing that turgor-driven changes in the growth rate do not cause comparable changes in PEx. For Avena coleoptiles, PEx appears to be a measure of the average Φ over the previous 60–90 min rather than a measure of the instantaneous Φ of the growth equation. This is indicated by the fact that while PEx and the growth rate start to change simultaneously after addition of indole-3-acetic acid or KCN, the growth rate reaches a new, constant value 60–90 min before a new plateau value of PEx is obtained. Similar results are obrained with soybean (Glycine max L.) hypocotyl walls, indicating that the relationship between PEx and the parameter Φ is a general one, although the period over which Φ is averaged differs from tissue to tissue. In addition, it is shown that PEx can be measured more than once on the same section; a new potential for plastic extension is regenerated whenever the force vectors are changed even slightly. It is concluded that PEx is a measure of those domains in the wall where a wall-loosening event has occurred which has not been eliminated by further wall synthesis or other biochemical events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00411139
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  • 4
    Electronic Resource
    Electronic Resource
    Control of light-induced bean leaf expansion: Role of osmotic potential, wall yield stress, and hydraulic conductivity (1981)
    Springer
    Planta 153 (1981), S. 572-577 
    Details
    ISSN: 1432-2048
    Keywords: Cell wall (extensibility) ; Hydraulic conductivity ; Leaf growth ; Light and leaf growth ; Osmotic potential ; Phaseolus ; Yield stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of three-turgor-related cellular parameters, the osmotic potential (Ψ s), the wall yield stress (Y) and the apparent hydraulic conductivity (L'p), in the initiation of ligh-induced expansion of bean (Phaseolus vulgaris L.) leaves has been determined. Although light causes an increase in the total solute content of leaf cells, the water uptake accompanying growth results in a slight increase in Ψ s. Y is about 4 bar; and is unaffected by light. L'p, as calculated from growth rates and isopiestic measurements of leaf water potential, is only slightly greater in rapidly-growing leaves. The turgor pressure of growing cells is lower than that of the controls by about 35%. We conclude that light does not induce cell enlargement in the leaf by altering any of the above parameters, but does so primarily by increasing wall extensibility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385543
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  • 5
    Electronic Resource
    Electronic Resource
    Calcium and the mechanical properties of soybean hypocotyl cell walls: Possible role of calcium and protons in cell-wall loosening (1988)
    Springer
    Planta 176 (1988), S. 60-67 
    Details
    ISSN: 1432-2048
    Keywords: Calcium and cell walls ; Cell enlargement ; Glycine (cell enlargement) ; Hypocotyl ; Plastic extensibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of calcium in the mechanical strength of isolated cell walls of soybean (Glycine max (L.) Merr. cv. Wayne) hypocotyls has been investigated, using the Instron technique to measure the plastic extensibility (PEx) of methanol-boiled, bisected hypocotyl sections and epidermal strips, and atomic absorption spectroscopy to measure wall calcium. Plastic extensibility was closely correlated with the growth rate of intact soybean hypocotyls. Removal of calcium from isolated cell walls by ethylene glycol-bis(2-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA) or low pH increased PEx, while addition of calcium decreased PEx; both effects were reversible. The amount of calcium removed and the increase in PEx at pH 4.5 were strongly dependent upon the chelating ability of the buffer anion. There was a direct correlation between the amount of calcium removed from the wall by EGTA or acid and the increase in PEx. Removal of up to 60% of the calcium increased PEx of half-section up to two fold, but further loss of calcium caused a much greater increase in PEx. With epidermal strips, PEx increased only when calcium was reduced below a threshold. At pH 3.5, there was an additional increase in PEx after a lag of about 2 h; this additional increase may be the result of acid-induced cleavage of a different set of load-bearing bonds. We conclude that calcium bridges are part of the load-bearing bonds in soybean hypocotyl cell walls, and that breakage of these crosslinks by apoplastic acid participates in wall loosening. Acid-induced solubilization of wall calcium may be one mechanism involved in wall loosening of dicotyledonous stems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392480
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  • 6
    Electronic Resource
    Electronic Resource
    The role of the epidermis and cortex in gravitropic curvature of maize roots (1988)
    Springer
    Planta 176 (1988), S. 513-518 
    Details
    ISSN: 1432-2048
    Keywords: Auxin and root growth ; Gravitropism ; Growth control ; Root (gravitropism) ; Zea (gravitropism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to determine the role of the epidermis and cortex in gravitropic curvature of seedling roots of maize (Zea mays L. cv. Merit), the cortex on the two opposite flanks was removed from the meristem through the growing zone; gravitropic curvature was measured with the roots oriented horizontally with the cut flanks either on the upper and lower side, or on the lateral sides as a wound control. Curvature was slower in both these treatments (53° in 5 h) than in intact roots (82°), but there was no difference between the two orientations in extent and rate of curvature, nor in the latent time, showing that epidermis and cortex were not the site of action of the growth-regulating signal. The amount of cortex removed made no difference in the extent of curvature. Curvature was eliminated when the endodermis was damaged, raising the possibility that the endodermis or the stele-cortex interface controls gravitropic curvature in roots. The elongation rate of roots from which just the epidermis had been peeled was reduced by 0.01 mM auxin (indole-3-acetic acid) from 0.42 to 0.27 mm h-1, contradicting the hypothesis that only the epidermis responds to changes in auxin activity during gravistimulation. These observations indicate that gravitropic curvature in maize roots is not driven by differential cortical cell enlargement, and that movement of growth regulator(s) from the tip to the elongating zone is unlikely to occur in the cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397658
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  • 7
    Electronic Resource
    Electronic Resource
    General discussion on graviresponses (1997)
    Springer
    Planta 203 (1997), S. S170 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008106
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  • 8
    Electronic Resource
    Electronic Resource
    Stress relaxation of cell walls and the yield threshold for growth (1984)
    Springer
    Planta 162 (1984), S. 46-54 
    Details
    ISSN: 1432-2048
    Keywords: Cell expansion ; Cell wall stress relaxation ; Growth yield threshold ; Pisum (growth analysis) ; Turgor pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Theory predicts that, for growing plant cells isolated from a supply of water, stress relaxation of the cell wall should decrease cell turgor pressure (P) until the yield threshold for cell expansion is reached. This prediction was tested by direct P measurements of pea (Pisum sativum L.) stem cortical cells before and after excision of the growing region and isolation of the growing tissue from an external water supply. Cell P was measured with the micro-pressure probe under conditions which eliminated transpiration. Psychrometric measurements of water potential confirmed the pressureprobe measurements. Following excision, P of the growing cells decreased in 1 h by an average of 1.8 bar to a mean plateau value of 2.8 bar, and remained constant thereafter. Treatment with 10-5 M indole-3-acetic acid or 10-5 M fusicoccin (known growth stimulants) accelerated the rate of P relaxation, whereas various treatments which inhibit growth slowed down or completely stopped P relaxation in apical segments. In contrast, P of basal (nongrowing) segments gradually increased because of absorption of solutes from the cell-wall free space of the tissue. Such solute absorption also occurred in apical segments, but wall relaxation held P at the yield threshold in those segments which were isolated from an external water supply. These results provide a new and rapid method for measuring the yield threshold and they show that P in intact growing pea stems exceeds the yield threshold by about 2 bar. Wall relaxation is shown here to affect the water potential and turgor pressure of excised growing segments. In addition, solute release and absorption upon excision may influence the water potential and turgor pressure of nongrowing excised plant tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397420
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  • 9
    Electronic Resource
    Electronic Resource
    The role of extracellular free-calcium gradients in gravitropic signalling in maize roots (1991)
    Springer
    Planta 185 (1991), S. 379-384 
    Details
    ISSN: 1432-2048
    Keywords: Calcium and gravitropism ; Gravitropism(root) ; Root gravitropism ; Zea (root gravitropism)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gravitropism in roots has been proposed to depend on a downward redistribution of calcium across the root cap. However, because of the many calcium-binding sites in the apoplast, redistribution might not result in a physiologically effective change in the apoplasmic calcium activity. To test whether there is such a change, we measured the effect of gravistimulation on the calcium activity of statocyte cell walls with calcium-specific microelectrodes. Such a measurement must be made on a tissue with gravity sensing cells at the surface. To obtain such a tissue, decapped maize roots (Zea mays L. cv. Golden Cross Bantam) were grown for 31 h to regenerate gravitropic sensitivity, but not root caps. The calcium activity in the apoplasm surrounding the gravity-sensing cells could then be measured. The initial pCa was 2.60 ± 0.28 (approx 2.5 mM). The calcium activity on the upper side of the root tip remained constant for 10 min after gravistimulation, then decreased 1.7-fold. On the lower side, after a similar lag the calcium activity increased 1.6-fold. Control roots, which were decapped but measured before recovering gravisensitivity (19 h), showed no change in calcium activity. To test whether this gradient is necessary for gravitropic curvature, we eliminated the calcium activity gradient during gravitropism by applying a mobile calcium-binding site (di-nitro-BAPTA; 1,2-bis(2-amino-5-nitro-phenoxy)ethane-N,N,N′,N′-tetraacetic acid) to the root cap; this treatment eliminated gravicurvature. A calcium gradient may be formed by proton-induced calcium desorption if there is a proton gradient. Preventing the formation of apoplastic pH gradients, using 10 and 50 mM 2-(N-morpholino)ethanesulfonic acid (Mes) buffer or 10 mM fusicoccin to stimulate proton excretion maximally, did not inhibit curvature; therefore the calcium gradient is not a secondary effect of a proton gradient. We have found a distinct and rapid differential in the apoplasmic calcium activity between the upper and lower sides of gravistimulated maize root tips which is necessary for gravitropism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201060
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  • 10
    Electronic Resource
    Electronic Resource
    The contribution of tonoplast and plasma membrane to the electrical properties of a higher-plant cell (1978)
    Springer
    Planta 143 (1978), S. 261-265 
    Details
    ISSN: 1432-2048
    Keywords: Avena ; Cells (electric propeties) ; Electrical parameters ; Fusicoccin ; Plasmalemma ; Tonoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cytoplasm of subepidermal parenchyma cells of Avena sativa L. coleoptiles was collected at one end of the cell by centrifugation. The electrical properties of both plasmalemma and tonoplast were then examined with microelectrodes inserted into both cytoplasm and vacuole of the same cell. The input resistance of the cytoplasm measured with either electrode was 7.5±0.8 MΩ while that of the vacuole measured with the single vacuolar electrode and a bridge circuit was 29.2±3.1 MΩ. The latter value was not significantly different from that of control, uncentrifuged cells. The resistance of the tonoplast is therefore several times larger than the input resistance of the cytoplasm, but the specific resistance of the plasma membrane cannot be calculated without knowledge of the extent and pattern of intercellular coupling. Electrical coupling of the cytoplasms of adjacent cells was observed in only two out of eight experiments. The mean potential of the vacuoles,-77.8±6.4 mV, was not significantly different from that of the cytoplasm; however, all the available evidence indicates that variable tip potentials in impaled cells made absolute determination of the membrane potential uncertain. In fusicoccin, the cells hyperpolarized by 20 mV within 10 min. This reponse occurred entirely at the plasmalemma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391996
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