JXB Advance Access published online on April 2, 2008
Journal of Experimental Botany, doi:10.1093/jxb/ern040
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
An inland and a coastal population of the Mediterranean xero-halophyte species Atriplex halimus L. differ in their ability to accumulate proline and glycinebetaine in response to salinity and water stress
1Laboratoire de Biologie végétale, Faculté des Sciences de Tunis, Campus universitaire, 1060 Tunis, Tunisia
2Groupe de Recherche en Physiologie végétale, Université catholique de Louvain, 5 (Bte 13) Place Croix-du-Sud, 1348 Louvain-la-Neuve, Belgium
* These authors contributed equally to this work.
To whom correspondence should be addressed. E-mail: stanley.lutts{at}uclouvain.be
Soil salinity and drought compromise water uptake and lead to osmotic adjustment in xero-halophyte plant species. These important environmental constraints may also have specific effects on plant physiology. Stress-induced accumulation of osmocompatible solutes was analysed in two Tunisian populations of the Mediteranean shrub Atriplex halimus L.—plants originating from a salt-affected coastal site (Monastir) or from a non-saline semi-arid area (Sbikha)—were exposed to nutrient solution containing either low (40 mM) or high (160 mM) doses of NaCl or 15% polyethylene glycol. The low NaCl dose stimulated plant growth in both populations. Plants from Monastir were more resistant to high salinity and exhibited a greater ability to produce glycinebetaine in response to salt stress. Conversely, plants from Sbikha were more resistant to water stress and displayed a higher rate of proline accumulation. Proline accumulated as early as 24 h after stress imposition and such accumulation was reversible. By contrast, glycinebetaine concentration culminated after 10 d of stress and did not decrease after the stress relief. The highest salt resistance of Monastir plants was not due to a lower rate of Na+ absorption; plants from this population exhibited a higher stomatal conductance and a prodigal water-use strategy leading to lower water-use efficiency than plants from Sbikha. Exogenous application of proline (1 mM) improved the level of drought resistance in Monastir plants through a decrease in oxidative stress quantified by the malondialdehyde concentration, while the exogenous application of glycinebetaine improved the salinity resistance of Sbikha plants through a positive effect on photosystem II efficiency.
Key words: Atriplex halimus, glycinebetaine, halophyte, NaCl, osmotic adjustment, proline, salinity, water stress
Received 19 November 2007; Revised 20 January 2008 Accepted 23 January 2008