title: 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.
abstract: 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.
authors.affiliation: Laboratoire de Biologie végétale, Faculté des Sciences de Tunis, Campus universitaire, 1060 Tunis, Tunisia.
authors.forename: Abir
authors.initials: A
authors.lastname: Ben Hassine
authors.forename: Michel Edmond
authors.initials: ME
authors.lastname: Ghanem
authors.forename: Sadok
authors.initials: S
authors.lastname: Bouzid
authors.forename: Stanley
authors.initials: S
authors.lastname: Lutts
mesh_terms: D027466:Atriplex / Q000254:growth & development / Q000378:metabolism*; D001622:Betaine / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D008315:Malondialdehyde / Q000378:metabolism; D009997:Osmotic Pressure; D018384:Oxidative Stress; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018520:Plant Shoots / Q000254:growth & development / Q000378:metabolism; D011392:Proline / Q000378:metabolism*; D054712:Salinity; D012965:Sodium Chloride / Q000378:metabolism*; D014867:Water / Q000378:metabolism*
chemical_list: D045332:Photosystem II Protein Complex; D014867:Water; D002245:Carbon Dioxide; D001622:Betaine; D012965:Sodium Chloride; D008315:Malondialdehyde; D011392:Proline