Effect of Salicylic Acid Foliar Application on Growth Characteristics in Tomato (Lycopersicon esculentum L.) Under Lead Stress Conditions

The use of plant hormones has been introduced as a simple and suitable strategy to reduce the adverse effect of heavy metals in plants. To investigate the effect of salicylic acid (SA) in reducing lead (Pb) stress in tomato (Lycopersicon esculentum L.), a factorial experiment was conducted based on completely randomized design with three replications in the greenhouse of Razi University. Factors included soil Pb contamination at three levels (0, 150 and 300 mg kg-1 soil as Pb(NO3)2) and SA at three levels (0, 250 and 500 μM). Results showed that the highest proline content (23.4 mmol g-1) and Pb concentration (4.26 mg kg-1) were obtained in 300 mg kg-1 of Pb and 0 μM SA, which shows an increase of 303 and 387%, respectively, compared to the control (without Pb and SA). Also, the highest amount of soluble sugars (0.48 mg kg-1), plant height (43.5 cm), root length (18.3 cm/plant), shoot dry weight (7.48 g/plant), and leaf area (263.1 cm2/plant) were found in the treatment of 500 μM SA and 0 mg kg-1 Pb. In general, the results showed that the application of SA, as a plant hormone, is a simple and convenient method to reduce the adverse effects of Pb stress in tomato.