, Volume 188, Issue 1, pp 106–114 | Cite as

Spectral-dependence of light-inhibited hypocotyl elongation in photomorphogenic mutants ofArabidopsis: evidence for a UV-A photosensor

  • Jeff C. Young
  • Emmanuel Liscum
  • Roger P. Hangarter


Photon fluence rate-response curves at different wavelengths were generated for the light-induced inhibition of hypocotyl elongation in seedlings of wildtype and photomorphogenic mutants ofArabidopsis thaliana. (L.) Heynh. Treatment of wild-type seedlings with continuous low-fluence-rate light (< 1.0 μmol photons · m−2 · s−1) induced some inhibition of hypocotyl elongation at all wavelengths tested, with maximum inhibition in blue light. At higher fluence rates, inhibition reached a maximum of 70–80% in UV-A, blue, and far-red light. Fluence rate-response curves for seedlings ofblu1, a blue light-response mutant, showed a specific reduction in their response to blue light, but their response to UV-A, red, and far-red light was similar to that in wild-type seedlings. In contrast, the phytochromedeficient mutanthy6 showed a loss of response to lowfluence-rate light at all wavelengths, as well as to highfluence-rate far-red light. However,hy6 seedlings retained sensitivity to high-fluence-rate blue and UV-A light. The data support the conclusion that blue-lightand phytochrome-dependent photosensory systems regulate hypocotyl elongation independently and in an additive manner. Furthermore, hypocotyl inhibition in wild-type,blul, hy6 andblul-hy6 double mutants was indistinguishable in UV-A light, whereas marked differences were observed at other wavelengths, indicating the involvement of a third photosensory system with an absorption maximum in the UV-A.

Key words

Arabidopsis Photomorphogenesis Blue/UV-A light Hypocotyl elongation Phytochrome 


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Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • Jeff C. Young
    • 1
  • Emmanuel Liscum
    • 1
  • Roger P. Hangarter
    • 1
  1. 1.Department of Plant BiologyOhio State UniversityColumbusUSA

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