Patterns of auxin and abscisic acid movement in the tips of gravistimulated primary roots of maize

Plant Growth Regul. 1996;20:253-8. doi: 10.1007/BF00043315.


Because both abscisic acid (ABA) and auxin (IAA) have been suggested as possible chemical mediators of differential growth during root gravitropism, we compared with redistribution of label from applied 3H-IAA and 3H-ABA during maize root gravitropism and examined the relative basipetal movement of 3H-IAA and 3H-ABA applied to the caps of vertical roots. Lateral movement of 3H-ABA across the tips of vertical roots was non-polar and about 2-fold greater than lateral movement of 3H-IAA (also non-polar). The greater movement of ABA was not due to enhanced uptake since the uptake of 3H-IAA was greater than that of 3H-ABA. Basipetal movement of label from 3H-IAA or 3H-ABA applied to the root cap was determined by measuring radioactivity in successive 1 mm sections behind the tip 90 minutes after application. ABA remained largely in the first mm (point of application) whereas IAA was concentrated in the region 2-4 mm from the tip with substantial levels found 7-8 mm from the tip. Pretreatment with inhibitors of polar auxin transport decreased both gravicurvature and the basipetal movement of IAA. When roots were placed horizontally, the movement of 3H-IAA from top to bottom across the cap was enhanced relative to movement from bottom to top whereas the pattern of movement of label from 3H-ABA was unaffected. These results are consistent with the hypothesis that IAA plays a role in root gravitropism but contrary to the idea that gravi-induced asymmetric distribution of ABA contributes to the response.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Abscisic Acid / pharmacokinetics*
  • Gravitropism / physiology*
  • Herbicides / pharmacokinetics
  • Indoleacetic Acids / antagonists & inhibitors
  • Indoleacetic Acids / pharmacokinetics*
  • Phthalimides / pharmacokinetics
  • Plant Growth Regulators / pharmacokinetics*
  • Plant Root Cap / growth & development
  • Plant Root Cap / metabolism*
  • Plant Roots / growth & development
  • Plant Roots / metabolism
  • Zea mays / growth & development
  • Zea mays / metabolism*


  • Herbicides
  • Indoleacetic Acids
  • Phthalimides
  • Plant Growth Regulators
  • alpha-naphthylphthalamic acid
  • indoleacetic acid
  • Abscisic Acid