Abstract
Tomato seedlings (Lycopersicon esculentum Mill, cv Chibli F1) were subjected to different NaCl treatments (0, 25, 50 and 100 mM) during 10 days. Under low salinity (25 mM NaCl), tomato preserved a normal growth activity, associated with maintain of the tissues water status and a high selectivity for K+ over Na+. Under high salinity (50 and 100 mM), endogenous Na+ and CI− accumulations were contradicted by a decrease of K+ and NO3 − contents. Our results support the existence of a competition between K+/Na+ and NO3 −CI− at the level of uptake and storage process. The high salt stress (50 and 100 mM) emphasized a typical glycophytic behavior; displaying i) a severe decline in plant growth activity, ii) the low Na+ amounts compared to CI− in the leaves, make an evidence for Na+ extrusion from the leaves to the stems-petioles and roots, and iii) an inaptitude to use Na+ instead of K+ to carry out osmotic adjustments at high salinity (100 mM NaCl).
Résumé
De jeunes plants de Tomate (Lycopersicon esculentum Mill, cv Chibli F1) ont été soumis à différentes doses de NaCl (0, 25, 50 et 100 mM) pendant 10 jours. À faible dose de sel (25 mM), les plantes gardent une activité de croissance normale, associée au maintien de l'hydratation de leurs tissus ainsi qu'une forte sélectivité ionique en faveur des ions K+. À forte dose de NaCl (50 et 100 mM), l'accumulation des ions Na+ et Cl− est associée à une baisse des teneurs en nutriments, notamment en K+ et en NO3 −. Nos résultats suggèrent l'existence d'une compétition ionique entre Na+/K+ et Cl−/NO3 −. Les plantes manifestent un comportement glycophytique typique: i) chute de l'activité de croissance, avec une grande sensibilité de la partie aérienne, ii) exclusion des ions Na+ vers les tiges-pétioles et racines et iii) inaptitude de substituer K+ par Na+ pour rétablir l'équilibre osmotique au niveau des feuilles.
Abréviations
| Cl− | = |
chloride |
| NO3 − | = |
nitrate |
| Na+ | = |
sodium |
| PO4 2- | = |
phosphorus |
| S | = |
selectivity |
| SO4 2- | = |
sulfates |
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