Combined effect of foliar-applied salicylic acid and deficit irrigation on physiological–anatomical responses, and yield of squash plants under saline soil

• Foliar-applied salicylic acid (SA) improved growth of squash under water stress.
• Physiological and anatomical characters were positively altered by SA application.
• Yield and water-use efficiency have been increased by SA application.
• Foliar application of SA is recommended for crop production under water scarcity.

Salicylic acid (SA) controls plant growth and induces water deficit tolerance in plants. Summer and fall season experiments were conducted in 2013 to study the effect of 1 mM SA on growth, anatomy, yield, chlorophyll fluorescence, osmoprotectants and water use efficiency (WUE) of squash plants under three levels of irrigation (I100 = 100%, I80 = 80% and I60 = 60% of crop evapotranspiration. Growth, chlorophyll fluorescence, leaf anatomy, leaf photosynthetic pigments, total soluble sugars (TSS), proline, harvest index (HI), yield and WUE were significantly affected by both deficit irrigation (DI) and the combined DI + exogenously applied SA treatment. The combined DI + SA treatment modified the adverse effects of DI and enhanced all aforesaid parameters, while decreased proline concentrations. The combined treatment of I60 or I80 + SA produced plants having yields and WUE as produced with the plants generated under full irrigation conditions without SA treatment. From these results, we conclude that with exogenously applied 1 mM SA, the I60 or I80 strategy studied here could be successfully applied during summer and fall seasons for the production of commercial squash allowing water savings of 20%–40% without any detrimental effect on plant growth or yield.