Regulation of K + nutrition in plants

Abstract

Modern agriculture relies on mineral fertilization. Unlike other major macronutrients, potassium (K + ) is not incorporated into organic matter but remains as soluble ion in the cell sap contributing up to 10% of the dry organic matter. Consequently, K + constitutes a chief osmoticum to drive cellular expansion and organ movements, such as stomata aperture. Moreover, K + transport is critical for the control of cytoplasmic and luminal pH in endosomes, regulation of membrane potential, and enzyme activity. Not surprisingly, plants have evolved a large ensemble of K + transporters with defined functions in nutrient uptake by roots, storage in vacuoles, and ion translocation between tissues and organs. This review describes critical transport proteins governing K + nutrition, their regulation, and coordinated activity, and summarizes our current understanding of signaling pathways activated by K + starvation.