The Effects of Salicylic Acid and Silicon on Safflower Seed Yield, Oil Content, and Fatty Acids Composition under Salinity Stress

Soil and water salinization is a global treat for crop production and food security. Apply of phytohormones and nutrient management is a novel approach to reduce the negative impact of salinity. Hence the effects of salicylic acid (0, 600, 1200, and 1800 µM) and silicon (0, 1.5, and 2.5 mM) foliar application on safflower (Carthamus tinctorius L.) seed yield and quality were investigated under salt stress conditions (1.7, 7.5, and 15 dS m− 1). Salinity decreased capitulum number, seed number per capitulum, 100-seed weight, seed yield, oil percentage, oil yield, linoleic acid content, palmitic and linoleic acids yield, and seed potassium content. Application of salicylic acid (SA) and silicon (Si) increased biological and seed yield, oil content, oil yield, linoleic acid content, palmitic and linoleic acid yield but decreased stearic and oleic acid content and oleic acid yield. The harvest index (HI) was decreased with increasing salinity levels, indicating a stronger effect of salinity on seed yield more than biomass production. In contrast, SA and Si, whether alone or together, increased HI. The appropriate concentration of SA in saline and non-saline conditions was 1200 µM, but Si was different in salinity levels. Under non-stress and moderate stress conditions 2.5 mM Si showed better performance, while at severe salinity level, 1.5 mM Si showed an appropriate state. Oil content and quality improved by increasing linoleic acid and reducing stearic and palmitic acids by application of SA and Si. The content of seed elements with the application of salt, SA and Si showed different trends. Nitrogen content increased under salt stress, but potassium content decreased and sodium content did not change under saline and non-saline conditions. The application of SA and Si increased nitrogen and potassium content in stressed and non-stressed conditions, but had no significant effect on the amount of sodium.