Potassium homeostasis and signaling as a determinant of Echinacea species tolerance to salinity stress

Salt tolerant is strongly related to potassium (K+) retention in plant tissues under salt stress conditions. However, it is unclear for different Echinacea species. So, mechanistic basis of four Echinacea species (i.e. Echinacea purpurea, Echinacea angustifolia, Echinacea pallida, and Echinacea sanguinea) to salinity stress tolerance, and K+ retention were assessed in the present study. Non-invasive microelectrode ion flux measuring, DHAR and MDHAR activities, and pharmacological measurements were performed based on the standard methods. Ion flux measurements revealed higher K+ efflux in E. pallida and E. sanguinea species compared to the E. purpurea and E. angustifolia species in the elongation zone. Higher salinity-induced H+ efflux was found in the elongation zone than mature zone. However, E. angustifolia and E. purpurea had more Ca2+ influx compared to E. pallida and E. sanguinea species. Net K+ efflux decreased (> 90%) in the presence of TEA and GdCl3. Increasing of Ca2+ uptake and K+ loss in four Echinacea species roots were found in the presence of 0.3 mM Cu/Ascorbate (Cu/Asc). The significant role of H+-ATPase in H+ efflux was demonstrated by Sodium orthovanadate. Ultimately, the physiological properties of Echinacea species have a critical role in salinity-resistant/sensitive differences. Future scientific understanding of Echinacea species physiognomies may be necessary for better understanding of the plant behavior to salinity stress. One-sentence summaryHigher K+ efflux in E. pallida and E. sanguinea species as a result of NaCl and ROS act as a metabolic switch to save energy for adaptations and repairs in salinity stress conditions.