Salicylic Acid Induced Salinity Tolerance Through Manipulation of Ion Distribution Rather than Ion Accumulation

In this research, the effect of different SA concentrations (0, 0.5, 1.0, 1.5, and 2.0 mM) on biological and grain yield as well as Na⁺, K⁺, Cl^?, Ca²⁺, and Mg²⁺ distribution and accumulation in barley plants was examined under nonsaline (2 dS m^?1) and saline (12 dS m^?1) conditions in a three-year field study (2012–2015 growing seasons). Storage factor (SF) was defined as the concentration of an ion in the root, as a proportion of total uptake of that ion, to quantify ion partitioning between root and shoot. Salt stress decreased SF for K⁺, Ca²⁺, and Mg²⁺ and enhanced it for Na⁺ and Cl^?, which led to reduce grain and biological yield. Nonetheless, foliar-applied SA in varying concentrations could lower some of these adverse effects on ion transport and accumulation. At the 2nd and 3rd years, unfavorable climatic conditions such as less precipitation and higher temperature intensified salt stress and decreased the alleviating impact of SA. Foliar application of SA at higher levels increased SF for Na⁺ and Cl^? ions and decreased that for K⁺ indicating that SA helped barley plants keep more Na⁺ and Cl^? and less K⁺ ions in the root system, which suggested the probable role of SA in altering ion transport within the plant in favor of salt stress tolerance. SF was found to be more correlated with grain yield under both nonsaline and saline conditions. Overall, SF might be considered as a potential criterion for salt tolerance in barley plants.