Morpho-phytochemical attributes of Echinacea purpurea (L.) Moench exposed to salicylic acid and citric acid

The morpho-phytochemical responses of purple coneflower (Echinacea purpurea (L.) Moench) to foliar application of salicylic acid (SA) and citric acid (CA) at 0, 1, 5 and 10 mM (in four-leaves stage and two weeks later) were determined in a field experiment. The results indicated that elevated levels of SA and CA induce plant growth and biomass, including plant height, number of branches, leaves and flowers, fresh and dry weight of aerial parts and SPAD value. The highest flower number, flower yield/plant, shoot fresh and dry weight were obtained by 10 mM SA combined with 5 or 10 mM CA. DPPH radical scavenging activity increased about 1.9 fold with 5 or 10 mM SA combined with 10 mM CA. HPLC analysis revealed that SA and CA enhanced phenolic acids (cynaric acid, chichoric acid, echinacoside, chlorogenic acid and caftaric acid) production in plants. There was a significant positive correlation between number and yield of flowers with all morpho-phytochemical attributes except root weight. The data suggested that combination of SA and CA especially at 5 and 10 mM may have higher capacity to improve morpho-physiological traits and phenolic contents of E. purpurea.