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Auxin asymmetry during gravitropism by tomato hypocotylsGravitropic asymmetry of auxin was observed in hypocotyls of tomato (Lycopersicon esculentum Mill.) soon after horizontal placement: the ratio of apically supplied [3H]IAA collected from the lower sides to that from the upper sides was about 1.4 between 5 and 10 minutes. This was adequately early to account for the beginning of curvature. The auxin asymmetry ratio rose to about 2.5 between 20 and 25 minutes, and to 3.5 during the main phase of curvature. This compares reasonably well with the roughly 3.9 ratio for elongation on the lower side to elongation on the upper side that is the basis for the curvature. These data extend evidence that the Went-Cholodny theory for the mediation of tropisms is valid for dicot stems. Also consistent with the theory, an auxin asymmetry ratio of 2.5 was observed when wrong-way gravitropic curvature developed following application of a high level of auxin. In addition to reversing the asymmetry of elongation, the large supplement of auxin resulted in lower net elongation. Previous data established that ethylene is not involved in this decrease of growth as a function of increasing level of auxin.
Document ID
20040112084
Acquisition Source
Kennedy Space Center
Document Type
Reprint (Version printed in journal)
Authors
Harrison, M. A.
(Washington University Saint Louis, Missouri 63130)
Pickard, B. G.
Date Acquired
August 21, 2013
Publication Date
January 1, 1989
Publication Information
Publication: Plant physiology
Volume: 89
ISSN: 0032-0889
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NAG10-1022
CONTRACT_GRANT: NAGW-70
Distribution Limits
Public
Copyright
Other
Keywords
NASA Program Space Biology
NASA Discipline Number 40-99
NASA Discipline Number 29-20
NASA Program Space Biology Research Associates
Non-NASA Center
NASA Discipline Plant Biology

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