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Cortical and cap sedimentation in gravitropic Equisetum rootsAlthough the rootcap is required for gravitropic sensing, various classical and contemporary data raise the question of whether additional sensing occurs away from the cap in roots. Roots of Equisetum hyemale L. (horsetail) were examined by light and electron microscopy to determine which cell components were distributed with respect to gravity both in and away from the rootcap. Adventitious roots from stem cuttings were gravitropic in a vertical orientation or if reoriented to the horizontal. Obvious amyloplast sedimentation was found in vertical and in reoriented roots 1) in cells in the center of the rootcap and 2) in young, elongating cortical cells located in two to three layers outside the endodermis. These cortical amyloplasts were smaller than cap amyloplasts and, unlike central cap amyloplasts, were occasionally found in the top of the cell. The nucleus was also sedimented on top of the amyloplasts in both cell types, both in vertical and in reoriented roots. Sedimentation of both organelles ceased as cortical cells elongated further or as cap cells became peripheral in location. In both cell types with sedimentation, endoplasmic reticulum was located in the cell periphery, but showed no obvious enrichment near the lower part of the cell in vertical roots. This is the first modern report of sedimentation away from the cap in roots, and it provides structural evidence that gravitropic sensing may not be confined to the cap in all roots.
Document ID
20040090358
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Ridge, R. W.
(Ohio State University Columbus 43210)
Sack, F. D.
Date Acquired
August 21, 2013
Publication Date
March 1, 1992
Publication Information
Publication: American journal of botany
Volume: 79
Issue: 3
ISSN: 0002-9122
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NAGW-780
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Plant Biology
NASA Discipline Number 40-50
Non-NASA Center

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