Diffusive and Metabolic Limitations to Photosynthesis under Drought and Salinity in C3 Plants

J. Flexas; J. Bota; F. Loreto; G. Cornic; T. D. Sharkey

doi:10.1055/s-2004-820867

Plant Biology, Table of Contents

Plant Biol (Stuttg) 2004; 6(3): 269-279
DOI: 10.1055/s-2004-820867

Review Article

Georg Thieme Verlag Stuttgart KG · New York

Diffusive and Metabolic Limitations to Photosynthesis under Drought and Salinity in C₃ Plants

J. Flexas¹ , J. Bota¹ , F. Loreto² , G. Cornic³ , T. D. Sharkey⁴

¹Universitat de les Illes Balears, Palma de Mallorca, Balears, Spain
²CNR - IBAF, Monterotondo Scalo, Italy
³Université de Paris-Sud, Orsay, France
⁴University of Wisconsin-Madison, USA

Abstract

Drought and salinity are two widespread environmental conditions leading to low water availability for plants. Low water availability is considered the main environmental factor limiting photosynthesis and, consequently, plant growth and yield worldwide. There has been a long-standing controversy as to whether drought and salt stresses mainly limit photosynthesis through diffusive resistances or by metabolic impairment. Reviewing in vitro and in vivo measurements, it is concluded that salt and drought stress predominantly affect diffusion of CO₂ in the leaves through a decrease of stomatal and mesophyll conductances, but not the biochemical capacity to assimilate CO₂, at mild to rather severe stress levels. The general failure of metabolism observed at more severe stress suggests the occurrence of secondary oxidative stresses, particularly under high-light conditions. Estimates of photosynthetic limitations based on the photosynthetic response to intercellular CO₂ may lead to artefactual conclusions, even if patchy stomatal closure and the relative increase of cuticular conductance are taken into account, as decreasing mesophyll conductance can cause the CO₂ concentration in chloroplasts of stressed leaves to be considerably lower than the intercellular CO₂ concentration. Measurements based on the photosynthetic response to chloroplast CO₂ often confirm that the photosynthetic capacity is preserved but photosynthesis is limited by diffusive resistances in drought and salt-stressed leaves.

Key words

Diffusive limitations to photosynthesis - metabolic limitations to photosynthesis - drought - salinity - photosynthetic metabolism - stomatal-mesophyll conductance.

Full Text

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J. Flexas

Laboratori de Fisiologia Vegetal
Departament de Biologia
Universitat de les Illes Balears

Carretera de Valldemossa Km 7.5

07122 Palma de Mallorca, Balears

Spain

Email: jaume.flexas@uib.es

Editor: H. Rennenberg