The best salt solution parameter to describe seed/seedling responses to saline and sodic salts

Background and aims: Results of studies on plant responses to salt stress often are difficult to compare because different salt parameters were used. Our aim was to compare the effects of different combinations of sodium salts on germination/seedling growth of two forage species and determine which salt solution parameter(s) was(were) most closely related to these responses. Methods: Seeds of the legume Medicago sativa and the grass Elymus dahuricus were germinated in different concentrations of saline and sodic salts. Various parameters of the salt solutions were determined, and seed germination and seedling growth metrics were measured. Results: Seeds of both species were more tolerant to saline than to sodic salts, and seedlings of E. dahuricus were more salt tolerant than those of M. sativa. Na₂SO₄ and Na₂CO₃ were more inhibitory to germination/growth of the two study species than the same concentration of NaCl and NaHCO₃ for saline and sodic salts, respectively. For both species, electrical conductivity, salt content (%) and Na⁺ concentration best correlated with germination/growth for saline salts and Na⁺ concentration for sodic salts. Conclusions: In evaluating the effects of salt on seed germination and seedling growth, both saline and sodic salts need to be considered, and Na⁺ concentration is the best salt solution parameter to use in comparing and communicating the results.