Auxin Acts in Xylem-Associated or Medullary Cells to Mediate Apical Dominance

We have found similar results in Arabidopsis

Jonathan Booker; Steven Chatfield; Ottoline Leyser

2003

Scholarcy highlights

  • The central philosophy in the study of the regulation of plant shoot architecture is the concept of apical dominance, whereby the growing apical meristem suppresses the growth of axillary meristems, lying in the axils of leaves below it
  • To determine whether auxin is transported into Arabidopsis axillary buds, the distribution of radiolabeled indole-3-acetic acid applied to isolated nodes was analyzed
  • Isolated 22-mm nodal stem sections, containing an axillary bud that had not grown out, were excised from the secondary inflorescences of soil-grown plants and placed in microfuge tubes containing 30 ␮L of Arabidopsis thaliana salt nutrient solution supplemented with 1 ␮M 14C-IAA, a level sufficient to inhibit the outgrowth of buds in isolated nodes
  • Applied IAA was transported along the stem segment significantly more than basally applied IAA, and this basipetal transport was blocked by the polar auxin transport inhibitor naphthoxyacetic acid
  • There is strong evidence that apically derived auxin inhibits the outgrowth of axillary buds, many questions remain regarding how this effect is mediated
  • Such linkage is important in elucidating the pathways by which auxin represses axillary bud growth
  • Several downstream messengers may be required, with some involved in transmitting the signal into the bud and others synthesized and acting in situ in the bud

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