Salicylic acid induces salinity tolerance in tomato (Lycopersicon esculentum cv. Roma): associated changes in gas exchange, water relations and membrane stabilisation

The present study investigates the role of salicylic acid (SA) in inducing plant tolerance to salinity. The application of 0.1 mM SA to tomato [Lycopersicon esculentum Mill.] plants via root drenching provided protection against 150 mM or 200 mM NaCl stress. SA treated plants had greater survival and relative shoot growth rate compared to untreated plants when exposed to salt stress. At 200 mM salt, shoot growth rates were approximately 4 times higher in SA treated plants than untreated plants. Application of SA increased photosynthetic rates in salt stressed plants and may have contributed to the enhanced survival. Transpiration rates and stomatal conductance were also significantly higher in SA treated plants under saline stress conditions. SA application reduced electrolyte leakage by 44% in 150 mM NaCl and 32% in 200 mM NaCl, compared to untreated plants, indicating possible protection of integrity of the cellular membrane. Beneficial effects of SA in saline conditions include sustaining the photosynthetic/transpiration activity and consequently growth, and may have contributed to the reduction or total avoidance of necrosis. SA, when used in appropriate concentrations, alleviates salinity stress without compromising the plants ability for growth under a favourable environment.