Potassium/sodium steady-state homeostasis in Thellungiella halophila and Arabidopsis thaliana under long-term salinity conditions

Salinity is one of the most important abiotic stresses that challenges plant growth and development. Crops are glycophytes and salinity causes important losses in agriculture. One of the approaches to reduce salinity impact is to increase crop salt tolerance by transferring genetic determinants important for salt tolerance from halophytes to crop species. These determinants may be identified by comparative studies in model species that differ in their salt tolerance. Thus, some recent studies have been focused on the comparison of Arabidopsis thaliana and Thellungiella halophila. To further gain insights into mechanisms important for salt tolerance we present here a comparative study of salt tolerance in these two species. This study is performed in plants growing hydroponically with salinity under steady-state conditions, allowing a characterization of K+/Na+ homeostasis under conditions that are closer to those that the plants face in the field. The results show that T. halophila shows a higher root/shoot ratio under non-salt conditions than A. thaliana and that this difference is exacerbated under salinity conditions. The presence of NaCl produced higher reductions of tissue K+ concentrations as well as of K+-specific absorption rates in A. thaliana than in T. halophila. On the other hand, A. thaliana showed higher rates of Na+ absorption and transport to the shoot. As a result T. halophila shows an overall K+/Na+ selectivity that may contribute to its higher salt tolerance.