Physiological adjustment to salt stress in Jatropha curcas is associated with accumulation of salt ions, transport and selectivity of K+, osmotic adjustment and K+/Na+ homeostasis

This study assessed the capacity of Jatropha curcas to physiologically adjust to salinity. Seedlings were exposed to increasing NaCl concentrations (25, 50, 75 and 100mm) for 15days. Treatment without NaCl was adopted as control. Shoot dry weight was strongly reduced by NaCl, reaching values of 35% to 65% with 25 to 100mm NaCl. The shoot/root ratio was only affected with 100mm NaCl. Relative water content (RWC) increased only with 100mm NaCl, while electrolyte leakage (EL) was much enhanced with 50mm NaCl. The Na+ transport rate to the shoot was more affected with 50 and 100mm NaCl. In parallel, Cl- transport rate increased with 75 and 100mm NaCl, while K+ transport rate fell from 50mm to 100mm NaCl. In roots, Na+ and Cl- transport rates fell slightly only in 50mm (to Na+) and 50 and 100mm (to Cl-) NaCl, while K+ transport rate fell significantly with increasing NaCl. In general, our data demonstrate that J.curcas seedlings present changes in key physiological processes that allow this species to adjust to salinity. These responses are related to accumulation of Na+ and Cl- in leaves and roots, K+/Na+ homeostasis, transport of K+ and selectivity (K-Na) in roots, and accumulation of organic solutes contributing to osmotic adjustment of the species.