Potassium: A Potent Modulator of Plant Responses Under Changing Environment

Potassium is an essential plant nutrient and required in large amounts for proper growth and reproduction of plants. Potassium is considered second only to nitrogen, when it comes to nutrients needed by plants, and is commonly considered as the "quality nutrient." However, its deficiency causes severe alteration in various physiological processes such as photosynthetic CO₂ fixation and impairment in utilization of photosynthates under abiotic stresses. On the other hand, exogenous application of potassium plays pivotal role in cell turgor maintenance, osmotic adjustments and regulates stomatal opening under various environmental cues. Many reports revealed that exogenous application of potassium boost antioxidant arsenal in plants under stressful conditions and showed significant role in mitigation of oxidative stress in plants. Additionally, many evidences showed that presence of potassium could greatly lower the reactive oxygen species (ROS) production by reducing activity of NAD(P)H oxidases and maintaining photosynthetic electron transport. In this chapter, we will shed light on the data related with the role of potassium-mediated regulatory functions against abiotic stresses, its possible molecular mechanisms for regulation of various physiological processes under changing environment, and its role in conferring tolerance against abiotic stresses. Lastly, we will discuss the cross talk of potassium with various phytohormones under stress and stress-free conditions.