Measurements of Geoelectric and Anxin‐Induced Potentials in Coleoptiles with a Refined Vibrating Electrode Technique

Grahm, L.

doi:10.1111/j.1399-3054.1964.tb08155.x

Cited by 51 publications

(30 citation statements)

References 22 publications

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“…The lack of geoelectric effect under anaerobic conditions has also been found by Grahm and Hertz (4) Bearing in mind the consistency between the results in this paper and those of Ball and Dyke (1), Harrison (6) and Wilkins and Warren (9), the fact that we cannot detect a geotropic response in coleoptiles under anaerobic conditions makes it impossible for us to accept the views of Dedolph et al (2) on the lack of a direct relationship between the geoelectric and geotropic responses. There is a large amount of evidence which shows that both phenomena occur as the result of a lateral gradient in auxin concentratioln being set up in the organs (3,4,5,8,11). The finding of Grahm and Hertz (5) that the geoelectric effect develops in Zea coleoptiles after a single decapitation is not evidence for the occurrence of the geoelectric effect in the absence of auxin.…”

Section: Methodsmentioning

confidence: 83%

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Geotropic Response of Coleoptiles under Anaerobic Conditions¹

Wilkins¹,

Shaw²

1967

Plant Physiol.

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Section: Methodsmentioning

confidence: 83%

“…A physiological tip wvould have developed in the 5-hour rest period between decapitation and the beginning of electrical measurements (8). Grahm (3) has indeed shown that the capacity to develop a geoelectric effect is lost in freshly decapitated coleoptiles, but returns after a fewv hours.…”

Section: Methodsmentioning

confidence: 99%

Geotropic Response of Coleoptiles under Anaerobic Conditions¹

Wilkins¹,

Shaw²

1967

Plant Physiol.

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“…The time course consists of two components, i.e. the initial component for the first 15 min of "wrong way" curvature (6,7,9) (5)(6)(7)9) and contributes to induction of H+ secretion, which is thought to initiate growth (17). Gravitropic gradients in pH have been documented (8); the visualized pattern of differential acid efflux became more intense as the curvature developed.…”

Section: Discussionmentioning

confidence: 99%

“…Statocytes on the lower side of the root depolarize, and statocytes on the upper side hyperpolarize. This electrical asymmetry is the earliest event in graviperception.In shoots, early workers observed a transverse electrical potential in the horizontally oriented shoots (4,5,16). Grahm and Herz measured the potential between the upper and lower sides for 1 h and observed the potential increase after 15 min (4).…”

mentioning

confidence: 99%

Electrical Potentials during Gravitropism in Bean Epicotyls

Imagawa

Toko²,

Ezaki

et al. 1991

Plant Physiol.

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An apparatus for measuring simultaneously the surface electrical potentials along epicotyl was developed to study the largely bending situation by gravity. Potentials increased on the upper side and decreased on the lower side after the horizontal placement. The time course of electrical changes consisted of two components which correspond to growth movements observed during gravitropism.The Cholodny-Went model of gravitropism in plants suggests that the asymmetric distribution of auxin results in a gravitropic response in shoots (14). The process leading to such an unequal auxin distribution is not known. Some investigators have suggested that auxin accumulation results from an electrical asymmetry between the upper side and the lower side in the horizontal position (1 1).In roots, electrical currents around a primary root after gravistimulation have been studied (1, 3), and also membrane potentials have been measured in lateral statocytes of vertically and nonvertically growing roots (2). The currents flow acropetally on the upper side of the root cap and basipetally on the lower side. Statocytes on the lower side of the root depolarize, and statocytes on the upper side hyperpolarize. This electrical asymmetry is the earliest event in graviperception.In shoots, early workers observed a transverse electrical potential in the horizontally oriented shoots (4,5,16). Grahm and Herz measured the potential between the upper and lower sides for 1 h and observed the potential increase after 15 min (4). Woodcock and Wilkins (15,16) and Wilkins (5) considered that asymmetric IAA distribution produced the electrical field across the gravitropically responding shoot during upward curvature. However, Tanada and Vinten-Johansen ( 11) observed the development of a positive electrical potential on the lower side approximately 1 min after horizontal placement. This time is less than the presumed gravitropic presentation time of the shoots. They suggested that Grahm and Hertz and others might have been unable to detect a fast positive gravielectrical effect. However, this experiment seems to need a reexamination because the electrical potentials on the lower side drift to negative in the vertical position (9).The explanation for the electrical potentials during gravitropism in epicotyls requires long-term, sensitive measurements of the potentials not only on the lower side but also on the upper side throughout the entire time course of gravitropism. We have measured the surface electrical potentials on the lower and upper surfaces of shoots by developing new measuring equipment that was not effected by the amount of gravicurvature. MATERIALS AND METHODS Plant MaterialEtiolated epicotyls of adzuki bean (Phaseolus angularis) seedlings were used. Seeds were soaked in distilled water (40 ± 1°C) for 4 h and were placed in trays on filter papers wetted with 0.1 mm KCI and 0.05 mM CaCl2 solution. The trays were kept in darkness at 30 ± 1°C. After 5 d, the seedlings were moved to plastic cases filled with 0.1 mm KCI, 0.05 mm CaC...

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“…If there is free IAA not moving in a stream in the coleoptile, then it seems likely to be more in evidence at high concentrations (7 Mm) than at low (0.3 Mm). To find it at the low concentration will, therefore, obviate the need to experiment also at the higher concentrations.…”

mentioning

confidence: 99%

Auxin Transport in Avena

Newman

1970

Plant Physiol.

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MIeasurements have been made on the initial stages of the transport of carbon-14-labeled indoleacetic acid in the coleoptile of Avena sativa L. Concentrations of mobile and immobilized indoleacetic acid are related to both distance and time during the first 2 hours after application of the indoleacetic acid at several concentrations to the top of the decapitated coleoptile.At the lowest concentration of indoleacetic acid applied (0.3 Among the recent investigations of the elusive and intriguing phenomenon of auxin transport, there is a dearth of detailed measurements of the distribution and physiological state of the auxin in the plant. The excellent work of Goldsmith and Thimann (6) on the distribution of carbon-14-labeled indoleacetic acid in the Avena coleoptile is often quoted, but that work dealt mainly with IAA distribution and movement at least 2 hr after application to the cut top. It is desirable also to know the distribution of IAA in the coleoptile at earlier times. At these times, the IAA concentration in the coleoptile is rising as the hormone stream moves down from the source at the top. These studies, while not of the normal transport of endogenous auxin, may illuminate some aspects of normal transport.To aid in the understanding of the transport process, it is also necessary to distinguish experimentally between IAA bile in the tissue and that which has been immobilized. Goldsmith and Thimann (6) did not attempt to make this distinction, whereas a complication noted by Scott and Briggs (22) is the presence of some free (not irreversibly immobilized) but nonmoving IAA. This paper is an attempt to fill some gaps in our knowledge of distributions at short times of both mobile and immobilized IAA.It is recognized (5) that the basipetal movement of auxin in the plant is generally an active process, as is implied by the name "transport," and requires metabolic energy from cellular activity. Models of the transport process often include the simple assumption that auxin is transported from cell to cell in amounts that are proportional to the (mobile) concentration difference between the adjacent cells (15). (A transfer under a concentration difference does not need to be an active process, but it could be.) The necessary consequence of this assumption is that the concentration of IAA, after application to the top, must be roughly a decreasing exponential function of distance. (In some literature it is called a "logarithmic" function.) The predicted "profile", or graph of concentration against distance, is steepest at the top and becomes progressively less steep lower down. This kind of profile was found by Goldsmith and Thimann (6) under the conditions of their experiments.Canny (1) has pointed out the difficulties of defining a front to the stream of IAA moving with such a profile. Goldsmith and Thimann (6), being aware of this, did not make detailed measurements in the region of the coleoptile where a front might have been found. Several lines of evidence, however, suggest that a clear fr...

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Measurements of Geoelectric and Anxin‐Induced Potentials in Coleoptiles with a Refined Vibrating Electrode Technique

Cited by 51 publications

References 22 publications

Geotropic Response of Coleoptiles under Anaerobic Conditions¹

Geotropic Response of Coleoptiles under Anaerobic Conditions¹

Electrical Potentials during Gravitropism in Bean Epicotyls

Auxin Transport in Avena

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Measurements of Geoelectric and Anxin‐Induced Potentials in Coleoptiles with a Refined Vibrating Electrode Technique

Cited by 51 publications

References 22 publications

Geotropic Response of Coleoptiles under Anaerobic Conditions1

Geotropic Response of Coleoptiles under Anaerobic Conditions1

Electrical Potentials during Gravitropism in Bean Epicotyls

Auxin Transport in Avena

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Geotropic Response of Coleoptiles under Anaerobic Conditions¹

Geotropic Response of Coleoptiles under Anaerobic Conditions¹