**3.9 Salicylic acid**

Salicylic acid (SA), a phenolic plant hormone, is widely known for its involvement in plant growth and development and modulation of plant stress responses. Exogenous SA supply has strengthened salinity stress-tolerance mechanisms in extensive studies [168, 169]. Reports are also available on a high bio-stimulatory capacity of SA for salinity tolerance involving positive regulation of the AsA-GSH cycle, elevated

accumulation of osmoprotectors, antioxidant enzyme activation, and increasing tolerance under ion toxicity and oxidative stress [34, 170–172]. In salinity-exposed *Vigna radiata*, the role of SA-induced accumulation of glycine betaine protected photosynthesis and growth against NaCl-accrued impacts in *V. radiata* as a result of the minimized accumulation of Na+ and Cl− ions and oxidative stress and maintained high GSH level and eventually reduced cellular redox environment [25]. In many instances, SA-mediated plant-salinity tolerance has SA-dose dependency [25, 40, 173, 174]. In salinity (100 mM NaCl)-exposed pepper (*Capsicum annuum*) plants, an exogenous supply of SA (0.5 mM) reduced leaf Na+ content and oxidative stress-related traits [171]. SA-supply mediated regulation of ROS-metabolism and AsA-GSH cycle has also been reported in plants under salinity stress [175]. In earlier studies, supplied SA-assisted mitigation of salinity stress impacts in plants involved characteristic changes in the expression pattern of GST-gene family members such as *SlGSTT2*, *SlGSTT3,* and *SlGSTF4* [176]; enhanced transcript level of antioxidant genes; *GPX1*, *GPX2*, *DHAR*, *GR*, *GST1*, *GST2*, *MDHAR,* and *GS* [177], and GORK channel-mediated control of K+ loss [178].
