Effects of Irrigation Regime and Foliar Application of Salicylic Acid and Spermine on the Contents of Essential Oil and Caffeic Acid Derivatives in Echinacea purpurea L.

This study investigated the effect of irrigation regimes and the foliar application of salicylic acid (SA) and spermine (SPM) on the content of essential oil (EO) and caffeic acid derivatives (cichoric acid, echinacoside, chlorogenic acid, caftaric acid, and cynarin) of purple coneflower. Water deficit increased the EO content in leaves and flowers. However, the content of caffeic acid derivatives in leaves, flowers, and roots were increased in some cases while in other cases they were decreased under water stress, depending on water level, caffeic acid compound, and the plant organ. SA and SPM application decreased the EO content in leaves and flowers under all irrigation regimes. Nonetheless, the application of SA and SPM increased the contents of caffeic acid derivatives in all plant organs and the highest changes were obtained by combined SA and SPM. The effects of SA were concentration-dependent. In short, the positive effects of SA on caffeic acid derivatives were greater compared to SPM.