In Tunisia, like in the other countries of the Mediterranean, tomato is ranked among the important vegetables in the economic sphere. Tunisia ranks as the first consumer of this vegetable in the world. However, tomatoes are exposed to multiple environmental stresses. In particular, salinity is the most stressful limiting factor to productivity. Salt tolerance of the tomato is susceptible to be ameliorated by genetic and physiologic ways. Salicylic acid (SA), a plant phenolic, is now considered as a hormone-like endogenous regulator, and its role in the defense mechanisms against biotic and abiotic stressors has been well documented. So, the aim of this study was to investigate the impact of exogenous application of SA (0.01 mM) on growth, nutritional behavior, and some metabolic parameters (total chlorophyll, soluble sugars, proline, and proteins) of tomato plants cv. Moneymaker exposed to NaCl (100 mM). Our results showed that the application of 0.01 mM SA to tomato plants via root drenching attenuate the depressive effect of salinity on plants. This amelioration results in stimulation of growth and development of plant. Under stress conditions, SA-treated plants exhibited more accumulation of photosynthetic pigments and K(+) contents. Thus, SA induces an increase in soluble sugars in roots and leaves; also, we noted the increase of proteins only in roots. Overall, the adverse effects of salt stress tomato plants were alleviated by the exogenous application of SA at vegetative stage, which upregulated nutrition and the accumulation of some organic solutes and osmoprotectors such sugars, proline, and proteins. So salicylic acid can be greatly used to enhance salt tolerance of tomato plants.

NaCI tolerance and ion transport were studied in four varieties of triticale. Five-day-old seedlings were transfered into liquid media containing NaCl (0 to 200 mM). Dry matter production, tissue water content, and ion accumulation were determined 10 days later. The 4 varieties differed in sensitivity to NaCI. Comparative analysis of their inorganic nutrition revealed that the most tolerant variety was the most efficient in limiting Na + transport into the shoot, and in taking up K + . These results suggest that the K '/Na' selectivity coefficient of the transport into the shoot could be used as a criterion for early selection for tolerance to NaCI.

The salinity tolerance and ion transport of 2-month-old seedlings of stone pine (Pinus pinea L.) grown in hydroponic solution containing various concentrations of NaCl (0-100 mM) were studied. The presence of salt of up to 100 mM did not significantly reduce growth. Seedling hydration was insensitive to salinity. High salt concentrations reduced K ? and Ca 2? uptake, root accumulation, and export to shoots. Na ? and Cl -ions, representing the major part of the ionic uptake, were effectively compartmentalized in vacuoles. We concluded that seedlings of stone pine cultivated hydroponically were highly tolerant to salt concentrations of up to 100 mM for a culture period of 38 days. This tolerance was associated with the accumulation of Na ? and Cl -ions in the shoots.

La tolérance à la salinité a été examinée chez Setaria verticillata L., graminée estivale à cycle court, en conditions contrôlées de laboratoire. Les semis ont été effectués sur de la tourbe commerciale et les plantules obtenues repiquées sur le même substrat imbibé par capillarité avec de l'eau distillée, éventuellement additionnée de NaCl (50 à 300 mM). La détermination de la masse de matière sèche des plantes après trois semaines de culture sur les différentes concentrations en NaCl montre que la sétaire est très sensible à la salinité. Pendant les premiers stades de son développement, la concentration en NaCl qui provoque 50% d'inhibition de la croissance pondérale est de l'ordre de 75 mM. La réduction de croissance semble associée à une forte accumulation de Na + dans la plante et à un déficit d'approvisionnement des organes aériens en K + . Cette sensibilité à NaCl se retrouve pendant la phase reproductive, après 3 mois de culture. Le sel affecte négativement les composantes du rendement. La capacité germinative des grains obtenus dans ces conditions diminue avec la concentration en NaCl du milieu de culture des plantes mères et s'annule pour ceux récoltés sur NaCl 300 mM.

The control of the K/Na selectivity of ion secretion into the root xylem is considered as important for tolerance to salinity. Triticale (X-Triticosecale Wittmack), a wheat-rye hybrid, is known for its robustness and its tolerance to environmental constraints (soil acidity, high temperatures, drought, salinity). When grown in hydroponics, with synthetic media, triticale seedlings tolerate NaCl concentrations up to 100 mM without growth rate reduction. Previous studies have emphasized the importance of two mechanisms as responsible for this tolerance, namely (i) the prevention of excess accumulation in shoots, and (ii) the maintenance of correct nutrition in shoots. Both these mechanisms are hypothesized to be attributable to root characteristics. We have studied this hypothesis using triticale (var. INRAT TCL8) seedlings grown in hydroponics on media containing and at different concentrations. Xylemic sap was sampled on detopped plants, and assayed for and A high selectivity for appeared when xylem sap was compared to medium, even at high NaCl concentration. For instance, in the presence of 200 mM NaCl, concentration in the sap was one order of magnitude higher, and concentration one order of magnitude lower, than the corresponding concentrations in the medium. These results support the hypothesis that high selectivity of xylem loading in roots is a major determinant of triticale tolerance to salinity.