Plant Growth Regulation

, Volume 39, Issue 2, pp 161–170 | Cite as

The effects of auxin on lateral root initiation and root gravitropism in a lateral rootless mutant Lrt1 of rice (Oryza sativa L.)

  • Tory Chhun
  • Shin Taketa
  • Seiji Tsurumi
  • Masahiko Ichii


Auxins control growth and development in plants, including lateral rootinitiation and root gravity response. However, how endogenous auxin regulatesthese processes is poorly understood. In this study, the effects of auxins onlateral root initiation and root gravity response in rice were investigatedusing a lateral rootless mutant Lrt1, which fails to formlateral roots and shows a reduced root gravity response. Exogenous applicationof IBA to the Lrt1 mutant restored both lateral rootinitiation and root gravitropism. However, application of IAA, a major form ofnatural auxin, restored only root gravitropic response but not lateral rootinitiation. These results suggest that IBA is more effective than IAA in lateralroot formation and that IBA also plays an important role in root gravitropicresponse in rice. The application of NAA restored lateral root initiation, butdid not completely restore root gravitropism. Root elongation assays ofLrt1 displayed resistance to 2,4-D, NAA, IBA, and IAA.This result suggests that the reduced sensitivity to exogenous auxins may be due tothe altered auxin activity in the root, thereby affecting root morphology inLrt1.

Auxin Gravitropism Lateral root initiation Lateral roots Mutant Rice 


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Copyright information

© Kluwer Academic Publishers 2003

Authors and Affiliations

  • Tory Chhun
    • 1
  • Shin Taketa
    • 1
  • Seiji Tsurumi
    • 2
  • Masahiko Ichii
    • 1
  1. 1.Faculty of AgricultureKagawa UniversityMikiJapan
  2. 2.Graduate school of Science and Technology (A.R., A.A., T.A.) and Radioisotope Research Center (S.T.)Kobe UniversityRokkodai, NadakuJapan

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