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The effect of light levels on daily patterns of chlorophyll fluorescence and organic acid accumulation in the tropical CAM tree Clusia hilariana

Franco, Augusto ; Haag-Kerwer, Angela ; Herzog, Britta ; Grams, Thorsten ; Ball, Erika ; Mattos, Eduardo ; Scarano, Fabio ; Barreto, Suzanne ; Garcia, Maria ; Mantovani, Andre ; Lüttge, Ulrich

Trees, 1996, Vol.10(6), pp.359-365 [Periódico revisado por pares]

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  • Título:
    The effect of light levels on daily patterns of chlorophyll fluorescence and organic acid accumulation in the tropical CAM tree Clusia hilariana
  • Autor: Franco, Augusto ; Haag-Kerwer, Angela ; Herzog, Britta ; Grams, Thorsten ; Ball, Erika ; Mattos, Eduardo ; Scarano, Fabio ; Barreto, Suzanne ; Garcia, Maria ; Mantovani, Andre ; Lüttge, Ulrich
  • Assuntos: Chlorophyll fluorescence quenching ; Citric acid ; Malic acid ; Photochemistry ; Photosynthetic electron transport
  • É parte de: Trees, 1996, Vol.10(6), pp.359-365
  • Descrição: Sandy plains are characteristic of the coastal region of Brazil. We investigated the diel patterns of changes in organic acid levels, leaf conductance and chlorophyll a fluorescence for sun-exposed and shaded plants of Clusia hilariana , one of the dominant woody species in the sandy coastal plains of northern Rio de Janeiro state. Both exposed and shaded plants showed a typical CAM pattern with considerable diel oscillations in organic acid levels. The degradation of both malic and citric acids during the midday stomatal closure period could lead to potential CO 2 fixation rates of 28 μmol m -2 s -1 in exposed leaves. Moreover, exposed leaves exhibited large increases in total non-photochemical quenching (q N ) accompanied by a substantial decrease in effective quantum yield during the course of the day. However, these potential high rates of CO 2 fixation and the increases in qn of exposed plants were not enough to maintain the primary electron acceptor of photosystem II (q A ) in a low reduction state, similar to that of shaded plants. As a result, there was a moderate increase in the reduction state of q A throughout the day. Most of the decline in photochemical efficiency of exposed leaves of C. hilariana was reversible, as evidenced by the high levels of pre-dawn potential quantum yields (F v /F m ) and their rapid recovery after sunset. However, the depletion of the organic acid pool in the afternoon resulted in an accentuated subsequent drop in F v /F m , suggesting that prolonged periods of water stress accompanied by high irradiance levels may expose plants of C. hilariana in unprotected habitats to the danger of photoinhibition.
  • Idioma: Inglês

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