Populus euphratica and Populus pruinosa, sister species in the Turanga Section (Salicaceae), growing in semi-arid saline areas are known for their high salinity tolerance. In this study, by combining growth level with Na+and K+contents, the expression level of vacuolar Na+/H+antiporters was investigated for NaCl-induced changes in P. euphratica and P. pru-inosa calli. Compared to P. euphratica, P. pruinosa calli grew well in 200 mM NaCl stress from 14 to 21 days. Increasing the stressed time caused an increase in Na+ content concomitant with a decrease in K+ content in P. euphratica calli, whereas, with the presence of 200 mM NaCl, K+content has a less increase in 14 and 21 days than in 7 days which was detected in P. pruinosa calli. The transcript levels of six genes coding for NHX-type Na+/H+ antiporters suggest that vacuolar NHX1-NHX6 antiporters play important roles in responding to salt stress in P. pruinosa. Our data suggest that there exists a higher salt tolerance for P. pruinosa than P. euphratica at the cellular level, Na+avoidance or accumulation is observed in cellular compartments, and that expression of NHX antiporters is linked to the accumulator phenotype.
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