Journal of Plant Growth Regulation

, Volume 21, Issue 4, pp 459–468

Exposure of Petunia Seedlings to Ethylene Decreased Apical Dominance by Reducing the Ratio of Auxin to Cytokinin

  • Darren L. Haver
  • Ursula K. Schuch
  • Carol J. Lovatt
Contributed Article

DOI: 10.1007/s00344-002-0022-3

Cite this article as:
Haver, D.L., Schuch, U.K. & Lovatt, C.J. J Plant Growth Regul (2002) 21: 459. doi:10.1007/s00344-002-0022-3

Abstract

Seedlings of Petunia x hybrida ‘Orchid’ treated with the ethylene-releasing compound ethephon at 0.9, 1.7, and 3.5 mM evolved ethylene at a higher rate as the concentration of ethephon increased. Regardless of the concentration of ethephon applied, ethylene evolution peaked 6 to 8 h following application. Evidence that ethephon application decreased apical dominance included an increase in the number of new nodes on the main stem and a sustained increase in the length of new and existing lateral shoots compared to the control (no ethephon). Plants treated with 3.5 mM ethephon developed mild chlorosis, whereas a concentration of 1.7 mM ethephon decreased apical dominance without phytotoxic effects. The auxin/cytokinin ratio decreased in the apical shoot section as early as 1 h after ethephon treatment. In contrast, a decrease in the ratio in the subapical shoot section was not detected until 24 h after ethephon application. Reduction in auxin/cytokinin ratio was a result of a decrease in indole-3-acetic acid (IAA) and an increase of zeatin riboside (ZR), but not isopentenyladenosine (iPA). These results suggest that exposing ‘Orchid’ petunia seedlings to ethylene via ethephon lowers the auxin/cytokinin ratio, thereby promoting the outgrowth of lateral shoots.

Keywords

Petunia x hybridaEthephonIndole-3-acetic acidIsopentenyladenosineZeatin ribosideLateral shootsPlant architecture

Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Darren L. Haver
    • 1
  • Ursula K. Schuch
    • 2
  • Carol J. Lovatt
    • 1
  1. 1.Department of Botany & Plant SciencesUniversity of CaliforniaCaliforniaUSA
  2. 2.Department of Plant SciencesUniversity Arizona, TucsonArizonaUSA