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Plant Physiol. Mar 1990; 92(3): 792–796.
PMCID: PMC1062370

Correlations between Gravitropic Curvature and Auxin Movement across Gravistimulated Roots of Zea mays1

Abstract

We compared the kinetics of auxin redistribution across the caps of primary roots of 2-day-old maize (Zea mays, cv Merit) seedlings with the time course of gravitropic curvature. [3H] indoleacetic acid was applied to one side of the cap in an agar donor and radioactivity moving across the cap was collected in an agar receiver applied to the opposite side. Upon gravistimulation the roots first curved upward slightly, then returned to the horizontal and began curving downward, reaching a final angle of about 67°. Movement of label across the caps of gravistimulated roots was asymmetric with preferential downward movement (ratio downward/upward = ca. 1.6, radioactivity collected during the 90 min following beginning of gravistimulation). There was a close correlation between the development of asymmetric auxin movement across the root cap and the rate of curvature, with both values increasing to a maximum and then declining as the roots approached the final angle of curvature. In roots preadapted to gravity (alternate brief stimulation on opposite flanks over a period of 1 hour) the initial phase of upward curvature was eliminated and downward bending began earlier than for controls. The correlation between asymmetric auxin movement and the kinetics of curvature also held in comparisons between control and preadapted roots. Both downward auxin transport asymmetry and downward curvature occurred earlier in preadapted roots than in controls. These findings are consistent with suggestions that the root cap is not only the site of perception but also the location of the initial redistribution of effectors that ultimately leads to curvature.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Evans ML. The action of auxin on plant cell elongation. CRC Crit Rev Plant Sci. 1985;2(4):317–365. [PubMed]
  • Evans ML, Moore R, Hasenstein KH. How roots respond to gravity. Sci Am. 1986 Dec;255(6):112–119. [PubMed]
  • Feldman LJ. Effect of auxin on acropetal auxin transport in roots of corn. Plant Physiol. 1981 Feb;67(2):278–281. [PMC free article] [PubMed]
  • Fett WF, Dunn MF. Exopolysaccharides Produced by Phytopathogenic Pseudomonas syringae Pathovars in Infected Leaves of Susceptible Hosts. Plant Physiol. 1989 Jan;89(1):5–9. [PMC free article] [PubMed]
  • Hasenstein KH, Evans ML. Effects of cations on hormone transport in primary roots of Zea mays. Plant Physiol. 1988;86:890–894. [PMC free article] [PubMed]

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