Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

Time-Dependent Changes in the Auxin Sensitivity of Coleoptile Segments: Apparent Sensory Adaptation

Mary Jo Vesper and Michael L. Evans
Plant Physiology
Vol. 61, No. 2 (Feb., 1978), pp. 204-208
Stable URL: http://www.jstor.org/stable/4265167
Page Count: 5
  • Read Online (Free)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Time-Dependent Changes in the Auxin Sensitivity of Coleoptile Segments: Apparent Sensory Adaptation
Preview not available

Abstract

When segments are excised from corn (Zea mays L.) coleoptiles they exhibit a very low rate of elongation for about 3.5 hours. A strong increase in growth rate (the spontaneous growth response) then occurs and persists for many hours. During the latent period preceding the spontaneous growth response there is an apparent increase with time in the sensitivity of the segments to indoleacetic acid (IAA). This increase in sensitivity is expressed as a 2- to 3-fold increase in the magnitude of the growth response to low levels of IAA and a 3-fold decrease in the latent period of the response during the first 3 hours following excision. A similar increase in sensitivity to low levels of IAA is noted if application of IAA is timed from the point of termination of a previous exposure to the hormone. Since the increase in responsiveness to low levels of IAA is not paralleled by an increase in the rate of uptake of the hormone, the data may be interpreted as evidence for a type of time-dependent sensory adaptation to auxin. The IAA dose-response relationship also changes with time, and there is indirect evidence that an auxin-dependent inhibitor may influence the expression of the apparent sensory adaptation to auxin.

Page Thumbnails

  • Thumbnail: Page 
204
    204
  • Thumbnail: Page 
205
    205
  • Thumbnail: Page 
206
    206
  • Thumbnail: Page 
207
    207
  • Thumbnail: Page 
208
    208