Improvement of growth parameters, flowering, and fruit of tomato under water deficit stress using seed pretreatment with salicylic acid

Water deficit is one of the most important stresses that has limiting effects on growth and crop productivity. One of the best methods for facing drought is seed priming with optimal concentrations of plant growth regulators. Salicylic acid (SA) is an important signal molecule modulating plant response to stress, which enhances tolerance to multiple stresses in plants, including drought. To analyze the effects of various concentrations of salicylic acid on some physiological and morphological traits as well as flower and fruit production of tomato, Riugerand variety, under water deficit conditions, a factorial experiment in a complete randomized design with three replications was carried out in the greenhouse. Six levels of salicylic acid (untreated seeds or control, zero SA or hydro-prim, 500, 1000, 1500, and 2000 mM) and three levels of drought stress (including water holding at field capacity [FC] of pots and water stress at 70% and 50% FC) were used as experimental treatments. Results showed that priming with salicylic acid increased plant height, leaf area, relative water content, and chlorophyll index compared to untreated plants. However, drought stress drastically decreased all these measured traits. 500 mM SA led to an increase in the number of flowers and fruits per plant as compared to other water deficit treatments. Tomato fruit characteristics, including pH, Brix, and EC, were significantly increased by drought stress. However, the application of SA decreased these traits, especially at 500 mM which enhanced the quality of the fruit. In conclusion, seed priming with suitable concentrations of SA (500 to 1000 mM) can be used as an appropriate strategy for the improvement of growth and fruit parameters of tomatoes under water deficit conditions.