Influence of high levels of Na+ and Cl− on ion concentration, growth, and photosynthetic performance of three salt-tolerant plants.

This study aimed to measure the effects of elevated levels of Na + and Cl − on ion concentration, growth, and photosynthetic performance of Melilotus siculus , Tecticornia pergranulata , and Thinopyrum ponticum in pot trials under controlled glasshouse conditions. Experiments were conducted using Na + and Cl − dominant saline soil treated with constituted saline solutions (0, 2.0 and 4.0 dS m −1 Na + or Cl − ). Maximum Na + and Cl − concentration was in T. pergranulata shoots; maximum Na + concentration was in T. pergranulata roots, whereas maximum Cl − in T. ponticum roots. Maximum quantum yield of PSII [Fv/Fm] values did not change significantly. Net-photosynthetic rate [ P n] and stomatal conductance [g s ] values increased and non-photochemical quenching [NPQ] value decreased significantly in T. pergranulata with increasing Na + dominant treatments and the reverse occurred in Cl − dominant treatments. Pn, g s , and NPQ values did not significantly change in T. ponticum with increasing Na + and Cl − dominant treatments. The shoot and root biomasses of T. pergranulata were the maximum at 4.0 dS m −1 Na + dominant treatment. In T. ponticum , the maximum shoot and root fresh masses and shoot dry mass occurred in the control treatment and the maximum root dry mass occurred in the 2.0 dS m −1 Cl − dominant treatment. In T. pergranulata , strong positive correlations occurred between Na + concentration in shoots and salt tolerance (shoot mass over control) and moderately positive correlation occurred between Cl − concentration in shoots and salt tolerance. However, strong negative correlations were observed between Na + and Cl − concentration in shoots and salt tolerance in T. ponticum as well as between Cl − concentration in shoots and salt tolerance in M. siculus . Our glasshouse experiments indicate that 4.0 dS m −1 Cl − solutions in the soil was more intensely damaging than that of Na + . The greatest concentration of both Na + and Cl − was in T. pergranulata under the tested circumstances indicating it to be the candidate of choice for restoring saline soils, followed in capacity by M. siculus and T. ponticum . [ABSTRACT FROM AUTHOR]