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@PHDTHESIS{Pieruschka:45486,
      author       = {Pieruschka, Roland},
      title        = {{E}ffect of internal leaf structures on gas exchange of
                      leaves},
      volume       = {56},
      school       = {Universität Düsseldorf},
      type         = {Dr. (Univ.)},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {PreJuSER-45486},
      isbn         = {3-89336-403-X},
      series       = {Schriften des Forschungszentrums Jülich. Reihe Umwelt /
                      Environment},
      pages        = {120 S.},
      year         = {2005},
      note         = {Record converted from VDB: 12.11.2012; Universität
                      Düsseldorf, Diss., 2005},
      abstract     = {Gas exchange of leaves is generally considered as the
                      interchange of gaseous compounds between the leaf interior
                      and ambient air. Once inside the leaf, CO$_{2}$ can diffuse
                      along its concentration gradients mainly regarded in the
                      vertical direction of the blade towards the assimilating
                      tissues. Lateral gas diffusion within intercellular air
                      spaces may be much more effective than has been considered
                      so far which depends on anatomical features of leaves. In
                      heterobaric leaves, lateral diffusion is restricted by
                      bundle-sheath extensions and the mesophyll is composed of
                      closed compartments. Homobaric leaves, however, lack such
                      extensions and the leaves have large interconnected
                      intercellular air spaces. The specific internal gas
                      diffusion properties of the leaves were characterized by gas
                      conductivities. Gas conductivity was larger in lateral than
                      in the vertical direction of homobaric leaf blades. However,
                      there was a large variability of the size and property of
                      the intercellular air space among different species. When
                      `clamp-on´ leaf chambers were used it was found that
                      lateral diffusion inside leaves seriously affected gas
                      exchange measurements. The impact of lateral CO$_{2}$
                      diffusion on gas exchange measurement was substantial when
                      exchange rates were low. Homobaric leaves showed internal
                      lateral gas fluxes when an overpressure was applied to the
                      leaf chamber which has been used in commercial gas exchange
                      systems to minimise the effects of leaks in the leaf
                      chamber. It was found here that overpressure affected
                      CO$_{2}$ and H$_{2}$O exchange rates of homobaric leaves
                      substantially larger than the theoretical direct impact of
                      air pressure on gas exchange processes. Gas gradients inside
                      leaves emerged when a leaf part was shaded and the adjacent
                      area of the leaf blade illuminated. Respiratory CO$_{2}$
                      evolved in the shaded region diffused to the illuminated
                      area were it was fixed by photosynthesis. These processes
                      obviously increased the photosynthetic efficiency along the
                      light/shade borderline as was visualized by chlorophyll
                      fluorescence imaging techniques. The recycling of
                      respiratory CO$_{2}$ from distant shaded areas was found to
                      be larger when stomatal conductance was low as is the case
                      under drought stress. Thus, when a homobaric leaf was
                      illuminated by lightflecks, additional CO$_{2}$ increased
                      the carbon gain, water use efficiency, and reduced light
                      stress. It was hypothesized that homobaric leaf anatomy is a
                      trait which has evolved under certain environmental
                      conditions.},
      cin          = {ICG-III},
      ddc          = {333.7},
      cid          = {I:(DE-Juel1)VDB49},
      pnm          = {Chemie und Dynamik der Geo-Biosphäre},
      pid          = {G:(DE-Juel1)FUEK257},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/45486},
}