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  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In December last, Dr. E. W. Hullett, director of the Wheat Research Institute, New Zealand, was in England, and directed the attention of one of us (T. M.) to this paper by Vuataz and the light it threw on his own earlier work. As a result, following a discussion with Dr. Hullett and Dr. E. ...
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 194 (1962), S. 1265-1266 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Du-lnositol Hexaphosphate AN investigation of the 'phytate' fraction of soil organic matter by Smith and Clark1, using a step-wise elution with increasing concentration of hydrochloric acid from an anion-exchange resin column, showed that in addition to small amounts of lower inositol phosphates ...
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 200 (1963), S. 568-569 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A gas-liquid chromatographic examination2 of the acetates of inositols isolated from the dephosphorylation of soil phytin preparations indicated the presence of a minor constituent (about 1 per cent) corresponding in retention time to the acetyl derivative of neo-inositol (I). neo-Inositol was ...
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 13 (1990), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The growth response of etiolated cucumber (Cucumis sativus L.) hypocotyls to gravitropic stimulation was examined by means of time-lapse photography and high-resolution analysis of surface expansion and curvature. In comparison with video analysis, the technique described here has five- to 20-fold better resolution; moreover, the mathematical fitting method (cubic splines) allows direct estimation of local and integrated curvature. After switching seedlings from a vertical to horizontal position, both upper and lower surfaces of the stem reacted after a lag of about 11 min with a two- to three-fold increase in surface expansion rate on the lower side and a cessation of expansion, or slight compression, on the upper surface. This growth asymmetry was initiated simultancously along the length of the hypocotyl, on both upper and lower surfaces, and did not migrate basipetally from the apex. Later stages in the gravitropic response involved a complex reversal of the growth asymmetry, with the net result being a basipetal migration of the curved region. This secondary growth reversal may reflect oscillatory and or self-regulatory behaviour of growing cells. With some qualifications, the kinetics and pattern of growth response are consistent with a mechanism involving hormone redistribution, although they do not prove such a mechanism. The growth kinetics require a growth mechanism which can be stimulated by two-to three-fold or completely inhibited within a few minutes.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: This study measured the electric and growth responses in excised cucumber hypocotyls and compared them with those in intact seedlings. Root excision (first severing cut) eliminated most of the positive xylem pressure (Px) in the hypocotyl, caused a rapid, transient drop in the hypocotyl growth rate (GR) and some small, local depolarization near the cut site. Although accompanied by a smaller decrease in Px, a second, severing cut in the basal hypocotyl caused a decrease in GR which was no longer transient and a depolarization which was increased in both size and extent. These changes were not wound effects because they could be simulated by root incubation in mannitol. The reduced GR recovery occurred also in the absence of electric changes after a second increase in the mannitol concentration incubating the root of intact seedlings. Increased electric sensitivity and altered growth response therefore appear to be two independent examples of physiological changes resulting from a lowered Px.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 16 (1993), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A variety of electrolytes (10–30 mol m−3) increased the relative growth rate of etiolated cucumber (Cucumis sativus L. cv. Burpee's Pickler) hypocotyls by 20–50% relative to water-only controls. The nonelectrolyte mannitol inhibited growth by 10%. All salts tested were effective, regardless of chemical composition or valence. Measurements of cell-sap osmolality ruled out an osmotic mechanism for the growth stimulation by electrolytes. This, and the nonspecificity of the response, indicate that an electrical property of the solutions was responsible for their growth-stimulating activity. Measurements of surface electrical potential supported this reasoning. Treatment with electrolytes also enhanced nutation and altered the pattern of phototropic curvature development. A novel analytical method for quantitating these effects on growth was developed. The evidence indicates that electrolytes influence an electrophysiological parameter that is involved in the control of cell expansion and the coordination of growth underlying tropisms and nutations.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Excision of a growing stem causes local wound responses, such as membrane depolarization and growth inhibition, as well as effects at larger distances from the cut. In this study, cucumber hypocotyls were excised 100mm below the hook, so that the growing region was beyond the reach of the wound-induced depolarization (up to 40mm). Even at such a distance, the cut still caused a considerable and rapid drop in the hypocotyl growth rate. This growth response is not a direct wound response because it does not result from the cut-induced depolarization and because it can be simulated by root pressure manipulation (using a pressure chamber). The results indicate that the growth response resulted from the rapid release of the xylem pressure upon excision. To test this conclusion we measured the xylem pressure by connecting a pressure probe to the cut surface of the stem. Xylem pressure (Px) was found to be +10 to +40kPa in cucumber hypocotyls and -5 to -10 kPa or lower in pea epicotyls. Excision of the cucumber hypocotyl base led to a rapid drop in Px to negative values, whereas excision in pea led to a rapid rise in Px to ambient (zero) pressure. These fast and opposite px changes parallel the excision-induced changes in growth rate (GR): a decrease in cucumber and a rise in pea.The sign of the endogenous xylem pressure also determined whether excision induced a propagating depolarization in the form of a slow wave potential (SWP). Under normal circumstances pea seedlings generated an SWP upon excision whereas cucumber seedlings failed to do so. When the Px in cucumber hypocotyls was experimentally inverted to negative values by incubating the cumber roots in solutions of NaCN or n-ethylmaleimide, excision caused a propagating depolarization (SWP). The experiment shows that only hydraulic signals in the form of positive Px steps are converted into propagating electric SWP signals. These propagating depolarizations might be causally linked to systemic ‘wound’ responses, which occur independently of the short-distance or direct wound responses.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 13 (1990), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The biophysical basis for the changes in cell elongation rate during gravitropism was examined in aetiolated cucumber (Cucumis sativus L.) hypocotyls. Bulk osmotic pressures on the two sides of the stem and in the epidermal cells were not altered during the early time course of gravitropism. By the pressureprobe technique, a small increase in turgor (0.3 bar, 30 kPa) was detected on the upper (inhibited) side, whereas there was a negligible decrease in turgor on the lower (stimulated) side. These small changes in turgor and water potential appeared to be indirect, passive consequences of the altered growth and the small resistance for water movement from the xylem, and indicated that the change in growth was principally due to changes in wall properties. The results indicate that the hydraulic conductance of the watertransport pathway was large (.25 h 1 bar 1) and the water potential difference supporting cell expansion was no greater than 0.3 bar (30 kPa). From pressureblock experiments, it appeared that upon gravitropic stimulation (1) the yield threshold of the lower half of the stem did not decrease and (2) the wall on the upper side of the stem was not made more rigid by a cross-linking process. Mechanical measurements of the stress/strain properties of the walls showed that the initial development of gravitropism did not involve an alteration of the mechanical behaviour of the isolated walls. Thus, gravitropism in cucumber hypocotyls occurs principally by an alteration of the wall relaxation process, without a necessary change in wall mechanical properties.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The positive xylem pressure (Px) in cucumber hypocotyls is a direct extension of root pressure and therefore depends on the root environment. Solutions of the electrolyte KCl (0.10 osm) reduced the hypocotyl Px transiently (biphasic response), while the Px reduction by mannitol solutions was sustained. The amplitudes of the induced Px reduction depended directly, and the degree of Px restoration after stress release depended indirectly, on the size of the initial positive Px, indicating that mannitol released the root pressure by a mechanical rather than osmotic mechanism. Mannitol treatment and other means of root pressure reduction revealed two separate growth responses in the affected cucumber hypocotyls. Only steep Px drops (following root excision or root pressure release in mannitol) directly cause a rapid, transient drop in growth rate (GR). Both rapid and slow (after root incubation in KCN or NEM) decreases in root pressure, however, led to a sustained growth inhibition of cucumber hypocotyls after about 30 min. This delay characterizes the growth response as an indirect consequence of the Px change. Pea seedlings, which lacked root pressure and had a negative Px throughout, showed extremely small changes in epicotyl Px and GR after root incubation in mannitol. It is apparent that the higher sensitivity of cucumber growth to mannitol depended on the presence and release of root pressure.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 17 (1994), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The local electric response to stem excision in both pea epicotyls and cucumber hypocotyls is a depolarization of the cells in the wound area. If we define wound area as the region of local depolarization, we find that it extends for approximately 10 mm from the cut or wound site in pea epicotyls, whereas it can reach up to 40 mm in cucumber hypocotyls. The wound-induced depolarization in pea cells is transient, reaching its maximal amplitude within 1–2 min, whereas in cucumber cells this depolarization is more sustained. A third difference between wound responses in pea and cucumber is the intermittent appearance of spikes, i.e. very short, rapidly reverted depolarizations which frequently accompany the basic depolarization in cucumber but not in pea cells. These spikes can propagate in both directions along the hypocotyl axis. The cause of the different responses of pea and cucumber cells is unknown. A possible explanation might be found in different degrees of electrical cell coupling in the two species. This possibility was investigated in cucumber hypocotyls by measuring the cell input resistance (Rin) of epidermal cells at various axial distances from the cut. Shorter distances increase the likelihood of shunting the cell membrane resistance through the shortened symplastic path to the cut surface. With a series of cuts made at decreasing distances from the measured site, cell depolarization increased without comparable changes in Rin. Two conclusions were drawn. Firstly, wound-induced depolarizations are not brought about by shunting of the cell resistance in the wound area. Secondly, the depolarization is probably not carried by ion channels but may be caused by an inhibition of proton pump activity. Parallel to its depolarizing effect on the membrane potential, excision led to a severe and sustained decline in the cucumber hypocotyl growth rate only when carried out sufficiently close to the growing region (45 mm from the hook). Similar excision in pea epicotyls failed to change the growth rate. Both electrical and growth data support the concept that the high and sustained responsiveness of cucumber seedlings to wounding is caused by a particular sensitivity of their proton pump mechanism.
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