Effect of the phytohormone salicylic acid on the salinity thresholds to seed germination and seedling growth in the oilseed Camelina sativa

The oilseed crop Camelina sativa exhibits salinity tolerance, but the effects on early growth stages across a range of different salts and in combination with salicylic acid (SA) have not been thoroughly evaluated. In this study, seeds were germinated in varying concentrations of six salts (NaCl, CaCl₂, ZnCl₂, KCl, MgSO₄, and Na₂SO₄) with or without 0.5 ​mM SA. Using the halotime model, we estimated salt thresholds for germination and parameters of seedling growth. Germination and seedling growth parameters of camelina significantly decreased with increasing salt concentration across all salt types. Salts containing Zn and SO4 were most detrimental to germination and seedling growth. Except for KCl, 0.5 ​mM SA generally reduced the salinity tolerance threshold (Saltb(50)) of camelina. Specifically, Saltb(50) was 21.5% higher for KCl and 16.1%, 25.0%, 54.9%, 21.0%, and 5.6% lower for CaCl₂, NaCl, MgSO₄, Na₂SO₄, and ZnCl₂, respectively, when 0.5 ​mM SA was compared to 0 ​mM SA. Furthermore, camelina seedling growth was consistently more sensitive than germination across all salt types. SA did not significantly enhance germination or seedling growth and was harmful when combined with certain salts or at the germination stage. It can be concluded that both the type of salt and the concentration of SA are as critical as the salt concentration in saline irrigation water.