Functional and biotechnological cues of potassium homeostasis for stress tolerance and plant development.

Potassium (K⁺) is indispensable for the regulation of a plethora of functions like plant metabolism, growth, development, and abiotic stress responses. K⁺ is associated with protein synthesis and entangled in the activation of scores of enzymes, stomatal regulation, and photosynthesis. It has multiple transporters and channels that assist in the uptake, efflux, transport within the cell as well as from soil to different tissues, and the grain filling sites. While it is implicated in ion homeostasis during salt stress, it acts as a modulator of stomatal movements during water deficit conditions. K⁺ is reported to abate the effects of chilling and photooxidative stresses. K⁺ has been found to ameliorate effectively the co-occurrence of drought and high-temperature stresses. Nutrient deficiency of K⁺ makes leaves necrotic, leads to diminished photosynthesis, and decreased assimilate utilization highlighting the role it plays in photosynthesis. Notably, K⁺ is associated with the detoxification of reactive oxygen species (ROS) when plants are exposed to diverse abiotic stress conditions. It is irrefutable now that K⁺ reduces the activity of NADPH oxidases and at the same time maintains electron transport activity, which helps in mitigating the oxidative stress. K⁺ as a macronutrient in plant growth, the role of K⁺ during abiotic stress and the protein phosphatases involved in K⁺ transport have been reviewed. This review presents a holistic view of the biological functions of K⁺, its uptake, translocation, signaling, and the critical roles it plays under abiotic stress conditions, plant growth, and development that are being unraveled in recent times.