The Source and Transport of Growth Regulators Responsible for the Geotropic Response of Zea mays Roots

  • Malcolm B. Wilkins
  • Griselda S. B. Gibbons
  • Stanley Shaw


The geotropic response of coleoptiles depends upon indole-3-acetic acid (IAA) synthesised in the apex of the organ. In a vertical Zea coleoptile, the IAA is transported basipetally into the elongating zone and symmetrically distributed, but in a horizontal coleoptile the IAA becomes asymmetrically distributed, the concentration in the lower half being greater than that in the upper half (Gillespie & Thimann, 1963; Goldsmith & Wilkins, 1964). Two apparently independent mechanisms give rise to this asymmetry: (1) a metabolically dependent, lateral, polar transport of IAA from the upper to the lower half of the organ (Goldsmith & Wilkins, 1964; Wilkins & Whyte, 1968; Cane & Wilkins, 1969); and (2) an enhanced basipetal transport of IAA in the lower, as compared with the upper, half of the organ (Naqvi & Gordon, 1966; Cane & Wilkins, 1969).


Lower Half Lower Side Auxin Transport Root Apex Intact Root 
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Copyright information

© Springer-Verlag Berlin · Heidelberg 1972

Authors and Affiliations

  • Malcolm B. Wilkins
    • 1
  • Griselda S. B. Gibbons
    • 1
  • Stanley Shaw
    • 1
  1. 1.Botany DepartmentThe UniversityGlasgowScotland. UK

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