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The effect of the external medium on the gravity-induced polarity of cytoplasmic streaming in Chara corallina (Characeae)Gravity induces a polarity of cytoplasmic streaming in vertical internodal cells of Chara such that the downwardly directed stream moves faster than the upwardly directed stream. In order to determine whether the statolith theory (in which intracellular sedimenting particles are responsible for gravity sensing) or the gravitational pressure theory (in which the entire protoplast acts as the gravity sensor) best explain the gravity response in Chara internodal cells, we controlled the physical properties of the external medium, including density and osmolarity, with impermeant solutes and examined the effect on the polarity of cytoplasmic streaming. As the density of the external medium is increased, the polarity of cytoplasmic streaming decreases and finally disappears when the density of the external medium is equal to that of the cell (1015 kg/m3). A further increase in the density of the external medium causes a reversal of the gravity response. These results are consistent with the gravitational pressure theory of gravity sensing since the buoyancy of the protoplast is dependent on the difference between the density of the protoplast and the external medium, and are inconsistent with the statolith theory since the buoyancy of intracellular particles are unaffected by changes in the external medium.
Document ID
20040089315
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Staves, M. P.
(Cornell University Ithaca, New York 14853, United States)
Wayne, R.
Leopold, A. C.
Date Acquired
August 21, 2013
Publication Date
November 1, 1997
Publication Information
Publication: American journal of botany
Volume: 84
Issue: 11
ISSN: 0002-9122
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Plant Biology

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