Transport, signaling, and homeostasis of potassium and sodium in plants

Potassium (K + ) is an essential macronutrient in plants and a lack of K + significantly reduces the potential for plant growth and development. By contrast, sodium (Na + ), while beneficial to some extent, at high concentrations it disturbs and inhibits various physiological processes and plant growth. Due to their chemical similarities, some functions of K + can be undertaken by Na + but K + homeostasis is severely affected by salt stress, on the other hand. Recent advances have highlighted the fascinating regulatory mechanisms of K + and Na + transport and signaling in plants. This review summarizes three major topics: (i) the transport mechanisms of K + and Na + from the soil to the shoot and to the cellular compartments; (ii) the mechanisms through which plants sense and respond to K + and Na + availability; and (iii) the components involved in maintenance of K + /Na + homeostasis in plants under salt stress.