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Auxin concentration/growth relationship for Avena coleoptile sections from seedlings grown in complete darkness.
MedLine Citation:
PMID:  16663419     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
A biphasic auxin dose-response curve has been obtained for indole-acetic acid (IAA)-stimulated growth of subapical sections of coleoptiles from totally dark-grown oats (Avena sativa L. cv Lodi). The curve for growth at 6 h is composed of a log-linear phase and a modified bell-shaped phase separated by a plateau. The curve is log-linear from 0.003 to 0.4 micromolar IAA when sections are incubated in pH 5.9 buffer. The plateau of IAA concentration-neutral growth is seen from 0.4 to 4.0 micromolar IAA. Further increase in growth occurs from 4.0 to 10 micromolar IAA. Changing the pH of the buffer from 5.9 to 5.5 or 6.2 changes the shape of the curve, shifting the plateau to lower IAA concentration, or abolishing it, respectively. The synthetic auxin 2,4-dichlorophenoxyacetic acid also shows a biphasic dose-response curve, but the synthetic auxin 1-naphthalene acetic acid does not. The plateau is not affected by the auxin-transport inhibitor 2,3,5-triiodobenzoic acid. The plateau is eliminated by taking sections from coleoptiles grown under continuous dim red light. We advance a model to account for these results based on two modes of auxin uptake into the cell: carrier-mediated uptake and uptake via chemiosmotic diffusion.
Authors:
J R Shinkle; W R Briggs
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Plant physiology     Volume:  74     ISSN:  0032-0889     ISO Abbreviation:  Plant Physiol.     Publication Date:  1984 Feb 
Date Detail:
Created Date:  2010-06-29     Completed Date:  2010-07-08     Revised Date:  2010-09-14    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  335-9     Citation Subset:  -    
Affiliation:
Department of Plant Biology, Carnegie Institution of Washington, Stanford, California 94305.
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