Experimental evidence and models on circumnutations

Johnsson, Anders; Heathcote, David

doi:10.1016/s0044-328x(73)80117-5

Cited by 61 publications

(47 citation statements)

References 40 publications

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“…6). An alternative interpretation ofthese data is that the R pulse induced or synchronized an oscillation (or nutation) in the roots (7) and that the response to a subsequent pulse of FR reflects an interaction with this nutation.…”

Section: Resultsmentioning

confidence: 94%

Photobiology of Diagravitropic Maize Roots

Mandoli

Tepperman²,

Huala³

et al. 1984

Plant Physiol.

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Light-induced modification of gravitropism in etiolated roots of Zea nays cv Bear x W38 is a low fluence response mediated by phytochrome. This cultivar has a threshold of 10-' mol m2 and becomes saturated with 10-2 mol m-2 of red light. The maximum light-mediated response of 32 degrees downward from horizontal occurs in roots 10 to 30 millimeters in length, 120 to 165 minutes after irradiation. Reciprocity is valid from 2 to at least 9,000 seconds and the response can be about 90% reversed by far red light. Photoreversibility is lost ('escape' occurs) about 20 minutes after red irradiation but appears to be regained 60 to 80 minutes later. A red light-induced (or synchronized) nutation in the apparent curvature rather than unusual escape characteristics may explain these results.Many roots are diagravitropic in darkness and change their response to gravity, becoming more orthogravitropic when exposed to light (2; review 24). The root cap is apparently the site of photoperception both for this change in gravitropism (14,15,25,26) and a general growth inhibition (16,26 broad band R,4 and determined the reciprocity characteristics and FR reversibility for this phenomenon. The ultimate aim is to elucidate the photobiology that governs directional growth of roots underground.MATERIAIS AND METHODS Zea mays (Bear x W38) caryopses were planted, imbibed, and grown in rows. Two rolls of modeling clay (Little Sculptor, 3M Co.) were positioned along the edges of a 1.5 x 17 cm black Plexiglas strip and about 20 maize caryopses were pressed into the clay so that all the embryos faced upward and in one direction. Each row was partially covered with water and imbibed in absolute darkness for at least 4 h. Styrofoam blocks, covered with absorbent paper (Kimpac, Kimberley-Clark) were placed inside opaque plastic boxes and the bottom of the boxes filled with deionized H20. The paper acted as a water wick for the duration of growth and treatment of the roots. Individual rows of imbibed seeds were placed into a rectangular groove which had been precut from a long edge of the styrofoam block, and the seedlings allowed to grow in the dark (95% humidity, 26C) for 2 d so that the roots grew out over the edge of the styrofoam block and above the water soaked paper. All manipulations were done in the absence of any light.Two-d-old roots were irradiated from above with broad band R or FR according to Mandoli and Briggs (10). After irradiation, seeds were grown for an additional time in the dark and then harvested in white light. Excised roots were arranged on lucite sheets and photocopied. Root lengths and angles were measured with a computerized digitizer (10). All experiments were done three times with 20 to 40 roots per datum point. SE per datum point rarely exceeded ±4°(e.g. Fig.

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Section: Resultsmentioning

confidence: 94%

Photobiology of Diagravitropic Maize Roots

Mandoli

Tepperman²,

Huala³

et al. 1984

Plant Physiol.

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“…Darwin's concept that the controlling mechanism for circumnutation must be internal, now generally referred to as the endogenous oscillator model (18) (18). The authors concluded that the controversy over whether or not a g-force is essential for circumnutation probably could be settled only by an experiment that would exploit the microgravity condition that prevails in earth orbit (11,17,18). The present paper reports the results of such an experiment.…”

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confidence: 87%

“…Amply supported by the next century of researchers, the ubiquity of circumnutation (still unexplained) has become the basis for a precisely defined scientific question-does gravity drive nutation or is the driver internal to the organism? Darwin's concept that the controlling mechanism for circumnutation must be internal, now generally referred to as the endogenous oscillator model (18) (18). The authors concluded that the controversy over whether or not a g-force is essential for circumnutation probably could be settled only by an experiment that would exploit the microgravity condition that prevails in earth orbit (11,17,18).…”

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confidence: 99%

Circumnutations of Sunflower Hypocotyls in Satellite Orbit

Brown

Chapman²,

Lewis³

et al. 1990

Plant Physiol.

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The principal objective of the research reported here was to determine whether a plant's periodic growth oscillations, called circumnutations, would persist in the absence of a significant gravitational or inertial force. The definitive experiment was made possible by access to the condition of protracted near weightlessness in an earth satellite. The experiment, performed during the first flight of Spacelab on the National Aeronautics and Space Administration shuttle, Columbia, in November and December, 1983, tested a biophysical model, proposed in 1967, that might account for circumnutation as a gravity-dependent growth response. However, circumnutations were observed in microgravity. They continued for many hours without stimulation by a significant g-force. Therefore, neither a gravitational nor an inertial g-force was an absolute requirement for initation or continuation of circumnutation. On average, circumnutation was significantly more vigorous in satellite orbit than on earth-based clinostats. Therefore, at least for sunflower (Helianthus annuus L.) circumnutation, clinostatting is not the functional equivalent of weightlessness.

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“…Plant organs display helical growth movements known as circumnutation (8)(9)(10)(11). These movements help plant organs find suitable environmental cues.…”

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confidence: 99%

Shoot circumnutation and winding movements require gravisensing cells

Kitazawa

Hatakeda

Kamada

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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Circumnutation and winding in plants are universal growth movements that allow plants to survive despite their sessile nature. However, the detailed molecular mechanisms controlling these phenomena remain unclear. We previously found that a gravitropic mutant of Japanese morning glory (Pharbitis nil or Ipomoea nil), Shidare-asagao (weeping), is defective not only in circumnutation but also in the winding response. This phenotype is similar to that of the Arabidopsis SCARECROW (SCR) mutant. We therefore investigated whether morning glory SCR (PnSCR) is involved in the weeping phenotype. We found that one amino acid was inserted into the highly conserved VHIID motif in weeping-type PnSCR; this mutation caused abnormal endodermal differentiation. We introduced either the mutant or WT PnSCR into Arabidopsis scr mutants for complementation tests. PnSCR of the WT, but not of weeping, rescued the shoot gravitropism and circumnutation of scr. These results show that both the abnormal gravitropism and the circumnutation defect in weeping are attributable to a loss of PnSCR function. Thus, our data show that gravisensing endodermal cells are indispensable for shoot circumnutation and the winding response and that PnSCR is responsible for the abnormal phenotypes of weeping.Arabidopsis ͉ gravitropic mutant ͉ gravity sensing ͉ morning glory ͉ SCARECROW

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Experimental evidence and models on circumnutations

Cited by 61 publications

References 40 publications

Photobiology of Diagravitropic Maize Roots

Photobiology of Diagravitropic Maize Roots

Circumnutations of Sunflower Hypocotyls in Satellite Orbit

Shoot circumnutation and winding movements require gravisensing cells

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