Plant Growth Regulation

, Volume 65, Issue 2, pp 263–271 | Cite as

Auxin stability and accumulation during in vitro shoot morphogenesis influences subsequent root induction and development in Eucalyptus grandis

  • Muhammad Nakhooda
  • M. Paula Watt
  • David Mycock
Original paper


Recent results showed that after 16 months in the field, micropropagated eucalyptus plants have an inferior root system to cuttings. Such differences may be due to the plant growth regulators supplied during the culture stages of standard protocols, which are targeted at optimising plantlet yields and not root quality. This study investigated such a proposal, focusing on auxins in an easy-to-root clone. Initial results showed that the auxin provided in the standard protocol (NAA for multiplication and IBA for elongation) enabled 100% rooting in auxin-free medium, where rooting was faster than on IBA-rooting media. When auxin supply was omitted from multiplication and restricted to NAA or IAA during elongation, rooting in an auxin-free medium was reduced to 68 and 31%, respectively, reflecting the stabilities of these auxins in plant tissues. Additionally, 15% of shoots from the NAA-medium and 65% from the IAA-medium produced roots with altered graviperception. GC–MS analysis of these shoots revealed a relationship between free IAA-availability and altered graviperception. This was further tested by adding the IAA-specific transport inhibitor 2,3,5-triiodobenzoic acid to rooting media with IBA, IAA or NAA, which resulted in 100, 70.9 and 20.6% rooting, respectively. At least 40% of the sampled root tips had atypical starch grain deposition and abnormal graviperception. It is proposed that, at least in this clone, while IBA and NAA can be used for in vitro root induction, IAA is necessary for development of graviresponse.


Eucalyptus Graviperception Plant growth regulators Root quality 



Altered graviperception


Gas chromatography-mass spectrometry


Indole-3-acetic acid


Indole-3-butyric acid


α-Naphthalene acetic acid


2,3,5-triiodobenzoic acid


Plant growth regulator



The National Research Fund, Universities of KwaZulu-Natal and Witwatersrand, and Mondi Business are gratefully acknowledged for continued funding for this research. M. Nakhooda also thanks the UKZN- LEAP programme for its support and Dr M. van der Merwe for expert assistance with the PGR assays.


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Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Muhammad Nakhooda
    • 1
  • M. Paula Watt
    • 1
  • David Mycock
    • 2
  1. 1.School of Biological and Conservation SciencesUniversity of KwaZulu-NatalDurbanSouth Africa
  2. 2.School of Animal, Plant and Environmental SciencesUniversity of the WitwatersrandJohannesburgSouth Africa

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