Enhancing salt tolerance of tomato (Solanum lycopersicum) by foliar application of aspirin (acetyl salicylic acid)

In Lebanon, soil salinity increasingly threatens the growth of various crops including tomato. Various methods have been adopted to alleviate the negative impacts of salinity. Here, aspirin application was evaluated as a method to counteract adverse salinity effects on tomato plants. Growth and production of tomato (Solanum lycopersicum 'Sila') irrigated with solutions of five salinity levels (EC=2, 4, 6, 8, and 10 dS m(-1)) were subjected to foliar application of aspirin (acetyl salicylic acid) in 3 different concentrations (A1: 50 mg L-1, A2: 75 mg L-1 and A3: 100 mg L-1) and compared to those of control plants grown under same salinity levels, but not treated with aspirin (A0). Plant height and fruit set recorded were close to control at 4, 6, and 8 dS m(-1) and the lowest values at 10 dS m(-1). On the other hand, leaf number and number of flowers were only affected by aspirin application with higher values in A1, A2, and A3 than the control. "Salinity" and "Aspirin application" had a combined effect on average stem diameter which was the lowest at EC=6 dS m(-1) and was improved by A1, A2 and A3. Average number of fruits was the lowest at 10 dS m(-1) despite treatment effect and the highest at A3 despite salinity effect. Aspirin did not enhance weight of individual fruit and fruit yield per plant which decreased with increasing salinity. Date of fruit maturity was similar in A1, A2 and A3 compared to A0 while fruit ripened earlier in A1, A2 and A3 than A0. Root Mass Fraction was the lowest at 10 dS m(-1) and was enhanced mainly at A1. Although aspirin application did not affect fruiting, it improved plant growth, root development and flowering characteristics under salt-stress.