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Circumnutations of sunflower hypocotyls in satellite orbitThe 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 initiation [correction of 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.
Document ID
20040090435
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Brown, A. H.
(Gravitational Plant Physiology Laboratory of the University City Science Center Philadelphia, Pennsylvania 19104-6017)
Chapman, D. K.
Lewis, R. F.
Venditti, A. L.
Date Acquired
August 21, 2013
Publication Date
January 1, 1990
Publication Information
Publication: Plant physiology
Volume: 94
ISSN: 0032-0889
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NAS39-15340
CONTRACT_GRANT: NGR39030-010
CONTRACT_GRANT: NGR39010-149
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Plant Biology
STS-9 Shuttle Project
Flight Experiment
NASA Discipline Number 00-00
NASA Program Flight
short duration
manned
NASA Discipline Number 29-20
NASA Program Space Biology
Non-NASA Center

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