Potassium use efficiency in crops under adverse environmental conditions

Potassium is one of the cornerstones of modern agriculture but its use in agricultural production systems is handicapped by the high cost of potash fertilizers and reduced potassium use efficiency (KUE) of crops under hostile environmental conditions. As the extent of abiotic stresses is predicted to increase under future current scenarios, improved KUE becomes an urgent task to ensure sustainability and profitability of agricultural production systems. This review reveals the mechanistic basis of KUE in plants, and effects of major abiotic stresses such as drought, salinity, heat, and soil waterlogging, on K⁺ acquisition, translocation, and utilization. The priority directions for improving KUE by genetic means are then discussed. This includes (1) Engineering crops for more efficient high-affinity K⁺ uptake systems; (2) understanding and improving operation of K⁺ sensing and signalling networks; (3) optimizing long-distance K transport and its source-sink allocation; and (4) substituting K⁺ with Na⁺ in some physiological processes.