It has been shown that salicylic acid (SA) acts as an endogenous signal molecule responsible for inducing stress tolerance. The aim of the present work is to investigate the effect of sodium chloride (0, 100, and 200 mM) and exogenous SA (1 mM) on some biochemical and molecular responses of safflower. Results revealed that K⁺, Ca²⁺, indol-3-acetic acid (IAA), and gibberellic acid (GA) contents decreased under salinity however, Na⁺ content, and SOS1 and NHX1 genes expression increased. Further, palmitic and oleic acids contents decreased, while stearic, linoleic, and linolenic acids content increased under salinity. Exogenous SA had a positive effect on K⁺, Ca²⁺, IAA, and GA contents, but decreased Na⁺ content. In addition, SA induced expression of SOS1 and NHX1 genes in all plants. Our data indicate that SA helps safflower to better cope with salinity. The results provide new insights to mechanisms that help regulate salinity resistance in safflower. SA may be considered as a foliar application to ameliorate salinity effects, due to its low price and availability.

The effects of salicylic acid (SA) on growth parameters and enzyme activities were investigated in salt-stressed safflower (Carthamus tinctorius L.). Twenty-five days after sowing, seedlings were treated with NaCl (0, 100, and 200 mM) and SA (1 mM), and were harvested at 21 days after treatments. Results showed that some growth parameters decreased under salinity, while malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) content, phenolic compounds, and some enzyme activities increased. SA application increased some growth parameters, MDA and H₂O₂ content, and enzyme activities except catalase (CAT), which was different from the other enzymes and SA significantly reduced CAT activity in plants. These results suggest that SA-induced tolerance to salinity may be related to regulation of antioxidative responses and H₂O₂ level. Our study suggested that the resistant safflower can direct reactive oxygen species from a threat to an opportunity by using SA. Therefore, exogenous application of SA played this role through regulation of the antioxidant system.