Comparative salt tolerance analysis between Arabidopsis thaliana and Thellungiella halophila, with special emphasis on K+/Na+ selectivity and proline accumulation

The eco-physiology of salt tolerance, with an emphasis on K+ nutrition and proline accumulation, was investigated in the halophyte Thellungiella halophila and in both wild type and eskimo-1 mutant of the glycophyte Arabidopsis thaliana, which differ in their proline accumulation capacity. Plants cultivated in inert sand were challenged for 3 weeks with up to 500 mM NaCl. Low salinity significantly decreased A. thaliana growth, whereas growth restriction was significant only at salt concentrations equal. to or exceeding 300mM NaCl. in T halophila. Na+ content generally increased with the amount of salt added in the culture medium in both species, but T halophila showed an ability to control Na+ accumulation in shoots. The analysis of the relationship between water and Na+ contents suggested an apoplastic sodium accumulation in both species; this trait was more pronounced in A. thaliana than in T halophila. The better NaCl tolerance in the tatter was associated with a better K+ supply, resulting in higher K+/Na+ ratios. It was also noteworthy that, despite highly accumulating proline, the A. thaliana eskimo-1 mutant was the most salt-sensitive species. Taken together, our findings indicate that salt tolerance may be partly linked to the plants' ability to control Na+ influx and to ensure appropriate K+ nutrition, but is not linked to proline accumulation. (C) 2007 Elsevier GmbH. All rights reserved.