Photosynthetic responses of soybean (Glycine max L.) to heat-induced electrical signalling are predominantly governed by modifications of mesophyll conductance for CO2

Authors

  • ALEXANDER GALLÉ,

    Corresponding author
    1. Grup de Recerca en Biologia de les Plantes en Condicions Mediterrànies, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, ES-07122 Palma de Mallorca, Spain
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    • These authors contributed equally to this work.

  • SILKE LAUTNER,

    1. Institute for Wood Biology, Universität Hamburg, Leuschnerstrasse 91, DE-21031 Hamburg, Germany
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    • These authors contributed equally to this work.

  • JAUME FLEXAS,

    1. Grup de Recerca en Biologia de les Plantes en Condicions Mediterrànies, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, ES-07122 Palma de Mallorca, Spain
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  • MIQUEL RIBAS-CARBO,

    1. Grup de Recerca en Biologia de les Plantes en Condicions Mediterrànies, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, ES-07122 Palma de Mallorca, Spain
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  • DAVID HANSON,

    1. Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
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  • JOHN ROESGEN,

    1. Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
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  • JÖRG FROMM

    1. Institute for Wood Biology, Universität Hamburg, Leuschnerstrasse 91, DE-21031 Hamburg, Germany
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A. Gallé. E-mail: alexander.galle@uib.es

ABSTRACT

In recent years, the effect of heat-induced electrical signalling on plant photosynthetic activity has been demonstrated for many plant species. However, the underlying triggers of the resulting transient inhibition of photosynthesis still remain unknown. To further investigate on this phenomenon, we focused in our present study on soybean (Glycine max L.) on the direct effect of signal transmission in the leaf mesophyll on conductance for CO2 diffusion in the mesophyll (gm) and detected a drastic decline in gm following the electrical signal, whereas the photosynthetic electron transport rate (ETR) was only marginally affected. In accordance with the drop in net photosynthesis (AN), energy dispersive X-ray analysis (EDXA) revealed a shift of K, Mg, O and P on leaf chloroplasts. Control experiments under elevated CO2 conditions proved the transient reduction of AN, ETR, the chloroplast CO2 concentration (Cc) and gm to be independent of the external CO2 regime, whereas the effect of the electrical signal on stomatal conductance for CO2 (gs) turned out much less distinctive. We therefore conclude that the effect of electrical signalling on photosynthesis in soybean is triggered by its immediate effects on gm.

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