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Lichens and Bryophytes: Light Stress and Photoinhibition in Desiccation/Rehydration Cycles – Mechanisms of Photoprotection

Heber, Ulrich ; Lüttge, Ulrich Lüttge, Ulrich (Editor) ; Beck, Erwin (Editor) ; Bartels, Dorothea (Editor)

Ecological Studies, Plant Desiccation Tolerance, pp.121-137

Berlin, Heidelberg: Springer Berlin Heidelberg 2011

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  • Título:
    Lichens and Bryophytes: Light Stress and Photoinhibition in Desiccation/Rehydration Cycles – Mechanisms of Photoprotection
  • Autor: Heber, Ulrich ; Lüttge, Ulrich
  • Lüttge, Ulrich (Editor) ; Beck, Erwin (Editor) ; Bartels, Dorothea (Editor)
  • Assuntos: Life Sciences ; Plant Ecology ; Plant Physiology ; Plant Genetics & Genomics ; Plant Biochemistry ; Plant Anatomy/Development ; Botany
  • É parte de: Ecological Studies, Plant Desiccation Tolerance, pp.121-137
  • Descrição: Many mosses and most of the lichens are desiccation-tolerant poikilohydrous cryptogams. By retaining their chlorophyll and their photosynthetic apparatus during desiccation, they are termed homoiochlorophyllous. In evolutionary terms, this is a primary adaptation. Photosynthetic pigments absorb light, whether the organisms are hydrated or desiccated, but energy conservation by carbon assimilation is possible only in the presence of water. When photosynthetic reaction centers remain intact during desiccation, photoreactions threaten to cause severe photooxidative damage. Shading or the production of sun-protectant pigments reduce but cannot prevent photooxidation. Mechanisms of harmless thermal energy dissipation provide far more efficient photoprotection than shading. Zeaxantin-dependent energy dissipation, usually sufficient to protect higher plants against excess illumination, is also operative in hydrated mosses and in lichens, which contain green algae as photobionts, but is not active in lichens with cyanobacteria as photobionts. During desiccation, other more efficient mechanisms of thermal energy dissipation are activated. They involve reversible changes of the conformation of a pigment protein, which facilitate ultrafast dissipation of the first excitation state of chlorophyll outside the reaction centers. Excitation energy is trapped in dissipation centers that are located in the near far-red region of the spectrum. They are connected to photosystem II. Additional protection may be provided by the reversible conversion of reaction centers into dissipation centers. Rehydration inactivates these mechanisms. Insight into the molecular mechanisms of thermal energy dissipation promises understanding of how oxidative damage is prevented in desiccated photoautotrophs under strong illumination.
  • Editor: Berlin, Heidelberg: Springer Berlin Heidelberg
  • Data de publicação: 2011
  • Idioma: Inglês

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