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Chronic ozone exposure preferentially modifies root rather than foliar metabolism of date palm (Phoenix dactylifera) saplings
  • +9
  • Leila Arab,
  • Yasutomo Hoshika,
  • Heike Müller,
  • Lorenzo Cotrozzi,
  • Cristina Nali,
  • Mariagrazia Tonelli,
  • Peter Ache,
  • Elena Paoletti,
  • Saleh Alfarraj,
  • Gadah Albasher,
  • Rainer Hedrich,
  • Heinz Rennenberg
Leila Arab
Chair of Tree Physiology, Institute of Forest Sciences, Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee 53, 79110 Freiburg, Germany

Corresponding Author:[email protected]

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Yasutomo Hoshika
IRET-CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino Firenze, Italy
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Heike Müller
Institute for Molecular Plant Physiology and Biophysics, Biocenter, University of Würzburg, 97082 Würzburg, Germany
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Lorenzo Cotrozzi
Department of Agriculture Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy
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Cristina Nali
Department of Agriculture Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy
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Mariagrazia Tonelli
Department of Agriculture Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy
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Peter Ache
Institute for Molecular Plant Physiology and Biophysics, Biocenter, University of Würzburg, 97082 Würzburg, Germany
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Elena Paoletti
IRET-CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino Firenze, Italy
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Saleh Alfarraj
King Saud University, PO Box 2455, Riyadh 11451, Saudi Arabia
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Gadah Albasher
King Saud University, PO Box 2455, Riyadh 11451, Saudi Arabia
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Rainer Hedrich
Institute for Molecular Plant Physiology and Biophysics, Biocenter, University of Würzburg, 97082 Würzburg, Germany
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Heinz Rennenberg
Chair of Tree Physiology, Institute of Forest Sciences, Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee 53, 79110 Freiburg, Germany
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Abstract

In their natural environment, date palms are exposed to chronic atmospheric ozone (O3) concentrations from local and remote sources. In order to elucidate the consequences of this exposure, date palm saplings were treated with ambient, 1.5 and 2.0 times ambient O3 for three months in a free-air controlled exposure facility. Chronic O3 exposure reduced carbohydrate contents in leaves and roots, but this effect was much stronger in roots. Still, sucrose contents of both organs were maintained at elevated O3, though at different steady states. Reduced availability of carbohydrate for the TCA cycle may be responsible for the observed reduced foliar contents of several amino acids, whereas malic acid accumulation in the roots indicates a reduced use of TCA cycle intermediates. Carbohydrate deficiency in roots, but not in leaves caused oxidative stress upon chronic O3 exposure, as indicated by enhanced malonedialdehyde, H2O2 and oxidized glutathione contents despite elevated glutathione reductase activity. Reduced levels of phenolics and flavonoids in the roots resulted from decreased production and, therefore, do not indicate oxidative stress compensation by secondary compounds. These results show that roots of date palms are highly susceptible to chronic O3 exposure as a consequence of carbohydrate deficiency.