An overview of potassium in abiotic stress: Emphasis on potassium transporters and molecular mechanism

Crop performance depends on their adaptability to agroecosystems and tolerance to a wide number of biotic and abiotic stresses. Potassium (K) is an essential mineral nutrient that directly or indirectly regulates plant growth and metabolism. It has been demonstrated that K contributes to enhance crop tolerance against abiotic and biotic stresses. It is important in plant nutrition and regulates many physiological and biochemical processes. Potassium deficiency reduces growth and development of plants, and under abiotic stress conditions, the damages become more severe. The use of fertilizers containing this macronutrient will increase with the higher demand of foods derived from the increase of worldwide population. Potassium plays a regulation role for different enzymes at transcriptional and posttranscriptional level. It is involved in the leaf transpiration, acting on the stomata opening. Therefore, potassium has a potential involvement in the drought and salinity stress tolerance. Potassium uptake is regulated by the highaffinity and low-affinity K+ uptake systems in plants. At molecular level, it has been demonstrated that this system in different environmental condition has directly involved in the potassium use efficiency (KUE) of crops. Since potassium has involved in different mechanism of abiotic stresses tolerance, the molecular studies can provide important details as improve the crop performance acting on the potassium uptake and translocation in plants. At physiological and biochemical levels, the abiotic stresses can affect potassium utilization in plants. In particular, it is important to highlight the interaction of potassium with other cations and anions. The cellular homeostasis can improve crop survival or performance under stressful conditions. Transcriptional profiles data on crops under potassium deficit can reveal the role of this macronutrient in plants and the potential correlation with the main abiotic stresses. In this chapter, the role of potassium in plants under different abiotic stress conditions and the expression profiles of the genes for K+ transporters will be reviewed.