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Stereological analysis of gravitropism in protonemata of the moss CeratodonApical cells of dark-grown protonemata of the moss Cerotodon purpureus are negatively gravitropic. Previous light microscopy has shown that reorientation to the horizontal induces amyloplast sedimentation and redistribution of microtubules. To determine whether other components become redistributed laterally or axially, the apical 35 micrometers of both vertical and horizontal apical cells were compared stereologically using transmission electron microscopy. Reorientation to the horizontal changed the longitudinal distributions of tubular ER, Golgi stacks, and vesicles but not cisternal ER, mitochondria, and plastids. Only plastids showed a statistically significant lateral redistribution after horizontal placement. Qualitative examination of the sedimentation zone showed plastids sedimented close to peripherally located ER with vacuoles displaced above plastids. These results argue against a model where differential tip growth results from a redistribution of Golgi stacks or exocytic vesicles.
Document ID
20040088977
Acquisition Source
Kennedy Space Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Walker, L. M.
(Ohio State University Columbus 43210, United States)
Sack, F. D.
Date Acquired
August 21, 2013
Publication Date
January 1, 1997
Publication Information
Publication: International journal of plant sciences
Volume: 158
Issue: 1
ISSN: 1058-5893
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NAGW-780
CONTRACT_GRANT: NAG10-0085
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Plant Biology

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