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.

Hormone-Induced Endoreduplication Prior to Mitosis in Cultured Pea Root Cortex Cells

Kornelis R. Libbenga and John G. Torrey
American Journal of Botany
Vol. 60, No. 4 (Apr., 1973), pp. 293-299
Stable URL: http://www.jstor.org/stable/2441195
Page Count: 7
  • Read Online (Free)
  • Download ($12.00)
  • 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.
Hormone-Induced Endoreduplication Prior to Mitosis in Cultured Pea Root Cortex Cells
Preview not available

Abstract

One-mm-thick cortical explants excised aseptically from 10-11 mm behind the tip of 3-day-old roots of the garden pea, Pisum sativum, cv. `Little Marvel' were cultured on a synthetic nutrient medium supplemented with auxin or auxin and cytokinin. Nuclear DNA contents were measured in cells of the explants at the outset and at specified times during culture up to seven days. Fixed and sectioned preparations were stained with the Feulgen method using the DNA-specific dye auramin-O. Fluorescent microspectro-photometric measurements of individual nuclei were made from each cortical population. At day zero all cortical nuclei measured were either 2c or 4c with respect to their DNA content. In the presence of the auxins, indoleacetic acid and 2,4-dichlorophenoxyacetic acid, and the cytokinin, kinetin, DNA values increased to multiples of the 2c level with populations at the 8c and 16c level predominating after three days of culture as well as at seven days. In the presence of auxins alone no change in DNA values was observed during three days. Kinetin concentrations as low as 0.01 ppm were already effective. The data are interpreted to show that cytokinin, in the presence of auxin, induces two rounds of DNA synthesis prior to the first mitoses, the first round being connected with chromosome doubling by endoreduplication and the second one with normal mitosis. From this we inferred that tetraploid cells in leguminous root nodules might have arisen in the same way, i.e., by endoreduplication prior to the first mitoses induced by the rhizobial division stimulus, unless the chromosome number of root cortical cells had already been doubled by endoreduplication in the normally differentiating root systems.

Page Thumbnails

  • Thumbnail: Page 
293
    293
  • Thumbnail: Page 
294
    294
  • Thumbnail: Page 
295
    295
  • Thumbnail: Page 
296
    296
  • Thumbnail: Page 
297
    297
  • Thumbnail: Page 
298
    298
  • Thumbnail: Page 
299
    299