Salt tolerance in two tall wheatgrass species is associated with selective capacity for Kplus over Naplus

Decaploid Elytrigia elongata (tall wheatgrass) is a halophytic relative of wheat that is used to improve salt tolerance of wheat in China. However, the physiological mechanisms for the salt tolerance of decaploid E. elongata remain elusive. To further gain insights into mechanisms important for salt tolerance, we present here a comparative study of salt tolerance in salt-sensitive tetraploid E. elongata (PI578686) and salt-tolerant decaploid E. elongata (PI276399). Results showed that compared with PI578686, PI276399 exhibited a higher relative growth rate and a stronger selective absorption and -transport capacity for K⁺ over Na⁺ under high salt conditions (100–200 mM NaCl). This contributed to maintain lower net Na⁺ uptake rates and more efficiently control Na⁺ transport to the shoot in PI276399 than in PI578686. Meanwhile, this also resulted in lower reductions of tissue K⁺ concentrations as well as of net K⁺ uptake rates in PI276399 compared to PI578686. Taken together, our findings indicate that PI276399 has the stronger selectivity for K⁺ over Na⁺ contributing it to maintain lower Na⁺ uptake and K⁺ loss compared with PI578686 in the presence of high salt, and hence endowing the higher salt tolerance of PI276399.