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Agricultural Journal
Year: 2011  |  Volume: 6  |  Issue: 6  |  Page No.: 353 - 365

Possible Involvement of Organic Compounds and the Antioxidant Defense System in Salt Tolerance of Medicago arborea (L.)

Faycal Boughalleb, Hichem Hajlaoui, Mahmoud Mhamdi and Mounir Denden    

Abstract: The possible involvement organic metabolites and the antioxidative defence system in salt tolerance were investigated in Medicago arborea (L.). Plants were subjected to three salt treatments, 100, 200 and 300 mM NaCl for 60 days under glasshouse conditions. The plant growth, leaf water content, solutes content, H2O2 generation, lipid peroxidation, membranes stability index, phenols accumulation and antioxidative enzymes activities were quantified in the roots and shoots. Increasing concentrations of salinity induced decrease in plant growth in both organs parts, especially in the shoots. In addition both shoots and roots were able to accumulate a large quantity of Na+ whereas the contents of K+ decreased significantly. Total soluble sugars and proline content were increased by salinity but do not seem to play an important role in osmoregulation. Indeed, leaf water content was reduced to 78.9% of the control at 300 mM NaCl, explaining the lower aptitude of M. arborea to adjust osmotically. After stress, the accumulation of phenols and the activities of the antioxidative enzymes were changed and the extent of alteration varied between the shoots and roots. Salt stress impacts in term of H2O2 generation and lipid peroxidation were more pronounced in the shoots than the roots. The relative antioxidative defence capacity in the leaves of M. arborea may be manly attained by the increasing activities of Superoxide Dismutase (SOD) and Catalase (CAT) at lower salt stress whereas at higher salinity the antioxidative defence might be achieved essentially by Peroxidase (POD), Ascorbate Peroxidase (APX) and several metabolites such as phenols and proline. In the roots, the scavenging system might be achieved by SOD, POD and APX activities which showed to participate efficiently in restriction of oxidative damages caused by the H2O2 generation.

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