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Residual nutational activity of the sunflower hypocotyl in simulated weightlessnessThe gravity dependence of circumnutational activity in the sunflower hypocotyl is investigated under conditions of simulated weightlessness. Seedling cultures of the sunflower Helianthus annuus were placed four days after planting in clinostats rotating at a rate of 1.0 rpm in the horizontal or somersaulting configurations, and plant movements around their growth axes were recorded in infrared light by a time-lapse closed-circuit video system. The amplitudes and mean cycle durations of the plant nutations in the horizontal and tumbling clinostats are observed to be 20% and 72%, and 32% and 74%, respectively, of the values observed in stationary plants; extrapolations to a state of zero g by the imposition of small centripetal forces on horizontally clinostated plants also indicate some nutational motion in the absence of gravity. It is concluded that the results are incompatible with the model of Israelsson and Johnsson (1967) of geotropic response with overshoot for sunflower circumnutation; however, results of the Spacelab 1 mission experiment are needed to unambiguously define the role of gravitation.
Document ID
19800037814
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Chapman, D. K.
(Pennsylvania Univ. Philadelphia, PA, United States)
Brown, A. H.
(Pennsylvania, University Philadelphia, Pa., United States)
Date Acquired
August 10, 2013
Publication Date
January 1, 1979
Publication Information
Publication: Plant and Cell Physiology
Volume: 20
Issue: 2, 19
Subject Category
Life Sciences (General)
Accession Number
80A21984
Funding Number(s)
CONTRACT_GRANT: NGR-39-010-149
CONTRACT_GRANT: NAS9-15340
CONTRACT_GRANT: NGR-39-030-010
Distribution Limits
Public
Copyright
Other

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