Foliar application of salicylic acid and proline to mitigate water deficit impact on purple coneflower (Echinacea purpurea (L.) Moench.)

Abstract

The effects of foliar spraying of salicylic acid and proline on Echinacea purpurea under different soil moistures were investigated in the field conditions in the Southwest of Iran (2017–2019). The experiment treatments were the foliar application of salicylic acid (SA) and proline (both at 1 mM concentration) and 2 irrigation frequencies (6 and 10 every day based on 75–80% and 40–45% field capacity, respectively). The field experiment was set as a complete randomized block design with 3 replications. The volatile oils were analyzed using GC-FID and GC-MS. Germacrene D, p-cymene, β-caryophyllene, α-pinene, and β-bisabolene were detected as the main constituents. Deficit irrigation decreased the growth parameters of the plants; however, it improved the contents of the volatile oil and the major compounds of volatile oil. In addition, the maximum values of the volatile oil content and the main constituents of volatile oil were extracted from the plants under SA × water deficit treatment. In conclusion, the foliar spraying of SA under water deficit conditions was an applicable strategy to maintain and stabilize the growth and yield of E. purpurea.