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@ARTICLE{Boonman:53460,
      author       = {Boonman, A. and Prinsen, E. and Gilmer, F. and Schurr, U.
                      and Peeters, A. J. M. and Voesenek, L.A.C.J. and Pons, T.
                      L.},
      title        = {{C}ytokinin import rate as a signal for photosynthetic
                      acclimation to canopy light gradients},
      journal      = {Plant physiology},
      volume       = {143},
      issn         = {0032-0889},
      address      = {Rockville, Md.: Soc.},
      publisher    = {JSTOR},
      reportid     = {PreJuSER-53460},
      pages        = {1841 - 1852},
      year         = {2007},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {Plants growing in dense canopies are exposed to vertical
                      light gradients and show photosynthetic acclimation at the
                      whole-plant level, resulting in efficient photosynthetic
                      carbon gain. We studied the role of cytokinins transported
                      through the transpiration stream as one of probably multiple
                      signals for photosynthetic acclimation to light gradients
                      using both tobacco (Nicotiana tabacum) and Arabidopsis
                      (Arabidopsis thaliana). We show that substantial variation
                      in leaf transpiration parallels the light gradient in
                      tobacco canopies and experimental reduction of the
                      transpiration rate of a leaf, independent of light, is
                      sufficient to reduce photosynthetic capacity in both
                      species, as well as transcript levels of the small subunit
                      of Rubisco (rbcS) gene in Arabidopsis. Mass spectrometric
                      analysis of xylem sap collected from intact, transpiring
                      tobacco plants revealed that shaded leaves import less
                      cytokinin than leaves exposed to high light. In Arabidopsis,
                      reduced transpiration rate of a leaf in the light is
                      associated with lower cytokinin concentrations, including
                      the bioactive trans-zeatin and trans-zeatin riboside, as
                      well as reduced expression of the cytokinin-responsive genes
                      ARR7 and ARR16. External application of cytokinin to shaded
                      leaves rescued multiple shade effects, including rbcS
                      transcript levels in both species, as did locally induced
                      cytokinin overproduction in transgenic tobacco plants. From
                      these data, we conclude that light gradients over the
                      foliage of a plant result in reduced cytokinin activity in
                      shaded leaves as a consequence of reduced import through the
                      xylem and that cytokinin is involved in the regulation of
                      whole-plant photosynthetic acclimation to light gradients in
                      canopies.},
      keywords     = {Adaptation, Physiological / Arabidopsis: metabolism /
                      Arabidopsis: physiology / Base Sequence / Biological
                      Transport / Chromatography, Liquid / Cytokinins: metabolism
                      / DNA Primers / Light / Photosynthesis / Reverse
                      Transcriptase Polymerase Chain Reaction / Tandem Mass
                      Spectrometry / Tobacco: metabolism / Tobacco: physiology /
                      Cytokinins (NLM Chemicals) / DNA Primers (NLM Chemicals) / J
                      (WoSType)},
      cin          = {ICG-3},
      ddc          = {580},
      cid          = {I:(DE-Juel1)ICG-3-20090406},
      pnm          = {Terrestrische Umwelt},
      pid          = {G:(DE-Juel1)FUEK407},
      shelfmark    = {Plant Sciences},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:17277095},
      pmc          = {pmc:PMC1851814},
      UT           = {WOS:000245781000033},
      doi          = {10.1104/pp.106.094631},
      url          = {https://juser.fz-juelich.de/record/53460},
}