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Altered growth response to exogenous auxin and gibberellic acid by gravistimulation in pulvini of Avena sativaPulvini of excised segments from oats (Avena sativa L. cv Victory) were treated unilaterally with indoleacetic acid (IAA) or gibberellic acid (GA3) with or without gravistimulation to assess the effect of gravistimulation on hormone action. Optimum pulvinus elongation growth (millimeters) and segment curvature (degrees) over 24 hours were produced by 100 micromolar IAA in vertical segments. The curvature response to IAA at levels greater than 100 micromolar, applied to the lower sides of gravistimulated (90 degrees) pulvini, was significantly less than the response to identical levels in vertical segments. Furthermore, the bending response of pulvini to 100 micromolar IAA did not vary significantly over a range of presentation angles between 0 and 90 degrees. In contrast, the response to IAA at levels less than 10 micromolar, with gravistimulation, was approximately the sum of the responses to gravistimulation alone and to IAA without gravistimulation. This was observed over a range of presentation angles. Also, GA3 (0.3-30 micromolar) applied to the lower sides of horizontal segments significantly enhanced pulvinus growth and segment curvature, although exogenous GA3 over a range of concentrations had no effect on pulvinus elongation growth or segment curvature in vertical segments. The response to GA3 (10 micromolar) plus IAA (1.0 or 100 micromolar) was additive for either vertical or horizontal segments. These results indicate that gravistimulation produces changes in pulvinus responsiveness to both IAA and GA3 and that the changes are unique for each growth regulator. It is suggested that the changes in responsiveness may result from processes at the cellular level other than changes in hormonal sensitivity.
Document ID
20040090283
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Brock, T. G.
(University of Michigan Ann Arbor 48109, United States)
Kaufman, P. B.
Date Acquired
August 21, 2013
Publication Date
January 1, 1988
Publication Information
Publication: Plant physiology
Volume: 87
ISSN: 0032-0889
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NAGW-34
Distribution Limits
Public
Copyright
Other
Keywords
NASA Program Space Biology
NASA Program Space Biology Research Associates
NASA Discipline Number 40-99
NASA Discipline Number 40-10
NASA Discipline Plant Biology
Non-NASA Center

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