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

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


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 subapicai 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.

Original languageEnglish (US)
Pages (from-to)459-468
Number of pages10
JournalJournal of Plant Growth Regulation
Issue number4
StatePublished - Dec 2002


  • Ethephon
  • Indole-3-acetic acid
  • Isopentenyladenosine
  • Lateral shoots
  • Petunia x hybrida
  • Plant architecture
  • Zeatin riboside

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Plant Science


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