Mesophyll conductance to CO2 in Arabidopsis thaliana

Authors

  • J. Flexas,

    1. Laboratori de Fisiologia Vegetal, Grup de Recerca en Biologia de les Plantes en Condicions Mediterrànies, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, 07122 Palma de Mallorca, Balears, Spain;
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    • *

      These authors contributed equally to this work.

  • M. F. Ortuño,

    1. Departamento Botânica e Engenharia Biológica, Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal;
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      These authors contributed equally to this work.

  • M. Ribas-Carbo,

    1. Laboratori de Fisiologia Vegetal, Grup de Recerca en Biologia de les Plantes en Condicions Mediterrànies, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, 07122 Palma de Mallorca, Balears, Spain;
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      These authors contributed equally to this work.

  • A. Diaz-Espejo,

    1. Instituto de Recursos Naturales y Agrobiología, CSIC, Apartado 1052, 41080 Sevilla, Spain
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  • I. D. Flórez-Sarasa,

    1. Laboratori de Fisiologia Vegetal, Grup de Recerca en Biologia de les Plantes en Condicions Mediterrànies, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, 07122 Palma de Mallorca, Balears, Spain;
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  • H. Medrano

    1. Laboratori de Fisiologia Vegetal, Grup de Recerca en Biologia de les Plantes en Condicions Mediterrànies, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, 07122 Palma de Mallorca, Balears, Spain;
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Author for correspondence: J. Flexas Tel: +34 971 173446 Fax: +34 971 173184 Email: jaume.flexas@uib.es

Summary

  • • The close rosette growth form, short petioles and small leaves of Arabidopsis thaliana make measurements with commercial gas exchange cuvettes difficult. This difficulty can be overcome by growing A. thaliana plants in ‘ice-cream cone-like’ soil pots.
  • • This design permitted simultaneous gas exchange and chlorophyll fluorescence measurements from which the first estimates of mesophyll conductance to CO2 (gm) in Arabidopsis were obtained and used to determine photosynthetic limitations during plant ageing from c. 30–45 d.
  • • Estimations of gm showed maximum values of 0.2 mol CO2 m−2 s−1 bar−1, lower than expected for a thin-leaved annual species. The parameterization of the response of net photosynthesis (AN) to chloroplast CO2 concentrations (Cc) yielded estimations of the maximum velocity of carboxylation (Vc,max_Cc) which were also lower than those reported for other annual species. As A. thaliana plants aged from 30 to 45 d, there was a 40% decline of AN that was entirely the result of increased diffusional limitations to CO2 transfer, with gm being the largest.
  • • The results suggest that in A. thaliana AN is limited by low gm and low capacity for carboxylation. Decreased gm is the main factor involved in early age-induced photosynthetic decline.

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