Jasmonic acid (JA) and salicylic acid (SA) are phytohormones that have a significant role in the induction of plant defense against different stress factors. The role of these phytohormones was assessed on several physicochemical properties of safflower plants subjected to salinity. JA and, especially SA, caused plants had more Na+ and less K+ content compared with the control plants. The JA and SA increased the catalase (CAT) activity, whereas significantly decreased the reactive oxygen species (ROS) production and lipid peroxidation in safflower plants under salinity stress. No significant effects of phytohormones were observed on peroxidase (POD) and ascorbate peroxidase (APX) activities in safflower plants exposed to salinity stress. Data on plant fluorescence indicated that seed priming with JA and SA decreases ROS production in photosystems. The effect of JA and SA under salinity stress was observed to significantly influence the light-dependent phase (J-I and I-P phases of chlorophyll a fluorescence curve) in comparison to the rest of the electron transport chain in safflower plants. This finding was supported by the high improvement of quantum yield of reduction of the end electron acceptors at the photosystem I acceptor side (φRo) activity under severe salinity stress. The observation indicated that the SA treatment was more effective in safflower plants exposed to salinity stress in comparison to the JA treatment.
