, Volume 212, Issue 3, pp 424-430

First online:

Red-light-induced positive phototropism in Arabidopsis roots

  • Nicholas J. RuppelAffiliated withDepartment of Botany, Miami University, Oxford, Ohio 45056, USA
  • , Roger P. HangarterAffiliated withDepartment of Biology, Indiana University, Bloomington, IN 47405, USA
  • , John Z. KissAffiliated withDepartment of Botany, Miami University, Oxford, Ohio 45056, USA

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The interaction between light and gravity is critical in determining the final form of a plant. For example, the competing activities of gravitropism and phototropism can determine the final orientation of a stem or root. The results reported here indicate that, in addition to the previously described blue-light-dependent negative phototropic response in roots, roots of Arabidopsis thaliana (L.) Heynh. display a previously unknown red-light-dependent positive phototropic response. Both phototropic responses in roots are considerably weaker than the graviresponse, which often masks phototropic curvature. However, through the use of mutant strains with impaired gravitropism, we were able to identify a red-light-dependent positive phototropic response in Arabidopsis roots. The red-induced positive phototropic response is considerably weaker than the blue-light response and is barely detectable in plants with a normal gravitropic response.

Key words:Arabidopsis (phototropism root) Gravitropism Phototropin Phototropism Phytochrome Root development