This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (14) Citing Articles via Google Scholar Google Scholar Articles by Shinkle, J. R. Articles by Briggs, W. R. Search for Related Content PubMed PubMed Citation Articles by Shinkle, J. R. Articles by Briggs, W. R. Agricola Articles by Shinkle, J. R. Articles by Briggs, W. R.

Articles

Auxin Concentration/Growth Relationship for Avena Coleoptile Sections from Seedlings Grown in Complete Darkness ¹

Department of Plant Biology, Carnegie Institution of Washington, Stanford, California 94305

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.

This article has been cited by other articles:

				M. Yamagami, K. Haga, R. M. Napier, and M. Iino Two Distinct Signaling Pathways Participate in Auxin-Induced Swelling of Pea Epidermal Protoplasts Plant Physiology, February 1, 2004; 134(2): 735 - 747. [Abstract] [Full Text] [PDF]