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Effects of increased gravity force on nutations of sunflower hypocotylsA centrifuge was used to provide sustained acceleration in order to study the hypocotyl nutation of 6-day-old Helianthus annuus L. over a range of g-forces, up to 20 times normal g. At the upper end of this g-range, nutation was impeded and at times was erratic evidently because the weight of the cotyledons exceeded the supportive abilities of the hypocotyls. Over the range 1 to 9 g, the period of nutation was independent of the resultant force vector. Over the same g-range, the amplitude of nutation was nearly independent of the chronic g-force. If nutation in sunflower seedlings is an oscillation caused by a succession of geotropic responses which continue to overshoot the equilibrium position (plumb line), its amplitude might be expected to be more sensitive to changes in magnitude of the sustained g-force. In order to preserve the geotropic model, in which nutation is considered to be a sustained oscillation driven by geotropic reactions, it is necessary to assume that geotropic response must increase with increasing g most rapidly in the region of the g-parameter below the terrestrial value of 1 g.
Document ID
19770060164
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Brown, A. H.
(Pennsylvania Univ. Philadelphia, PA, United States)
Chapman, D. K.
(Pennsylvania, University Philadelphia, Pa., United States)
Date Acquired
August 9, 2013
Publication Date
January 1, 1977
Publication Information
Publication: Plant Physiology
Volume: 59
Subject Category
Life Sciences (General)
Accession Number
77A43016
Funding Number(s)
CONTRACT_GRANT: NGR-39-010-149
CONTRACT_GRANT: NAS2-7730
CONTRACT_GRANT: NGR-39-030-010
CONTRACT_GRANT: NAS2-2432
CONTRACT_GRANT: NGR-39-010-104
CONTRACT_GRANT: NASW-2208
Distribution Limits
Public
Copyright
Other

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