To study the effect of foliar application of proline and salicylic acid on steviol glycosides and phenolic of Stevia, an experiment was conducted based on a completely randomized block design in a factorial arrangement with three replications in the University of Zanjan. Foliar application of proline in three levels (0, 1, 2 mM) as well as salicylic acid (0, 0.3, 0.6 mM) were applied after establishment of transplants in the field three time with 10 days intervals. Results showed that salicylic acid and proline applications significantly influenced on steviol glycosides, phenol and flavonoid. The treatment with salicylic acid had positive effects on all steviol glycosides, phenol and flavonoid, but proline only enhanced contents of glycosides stevioside, rebaudioside A, phenol and flavonoid. The highest average steviol glycosides stevioside (60.32 mg/g dw), rebaudioside A (24.14 mg/g dw) and total phenol (19.94 mg/g dw) was recorded in 1 mM proline in combination with 0.6 mM salicylic acid. The highest average flavonoid (10.02 mg/g dw), in 0.6 mM salicylic acid, and lowest average steviol glycosides and phenolic contents observed in control. Collectively, the results showed that application of proline and salicylic acid significantly improved production of active substances in Stevia rebaudiana.
