The effect of salt stress on lipid peroxidation and antioxidants in the leaf of the cultivated tomato and its wild salt-tolerant relative Lycopersicon pennellii

The possible involvement of the antioxidative system in the tolerance to salt stress was studied in the cultivated tomato Lycopersicon esculentum Mill. cv. M82 (M82) and its wild salt-tolerant relative L. pennellii (Corr.) D'Arcy accession Atico (Lpa). All analyses, except that of monodehydroascorbate reductase (MDHAR), were performed of the youngest fully-expanded leaf of control and salt (100 mM NaCl)stressed plants, 4, 7, 10, 14, 18 and 22 days after completing the stress treatment. In Lpa, constitutive level of lipid peroxidation and activities of catalase (CAT) and glutathione reductase (GR) were lower while the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) were inherently higher than in M82. Relative to M82, lipid peroxidation was much lower and the activities of SOD, CAT and APX were higher in Lpa at 100 mM NaCl. The activity of DHAR decreased more in Lpa than in M82 under salt stress, and the activity of MDHAR, which was lower in Lpa than in M82 under control conditions, increased much more and to a higher level in salt-treated Lpa plants. GR activity decreased similarly in the two species under salt stress. The results of these analyses suggest that the wild salt-tolerant Lpa plants are better protected against active oxygen species (AOS), inherently and under salt stress, than the relatively sensitive plants of the cultivated species.