Impact of potassium starvation on the uptake, transportation, photosynthesis, and abiotic stress tolerance

Potassium (K + ) plays a crucial role in plant homeostasis, and its deficiency significantly impacts photosynthesis, triggering a decrease in growth and crop production. K + starvation induced a significant reduction in the net photosynthetic rate, and the drop is associated with resistance of CO 2 diffusion through stomatal conductance, mesophyll conductance, and lowered carboxylase activity of Rubisco, electron transport rate of PSII, and with many biochemical limitations. The complex interaction of all the above factors contributed to limiting photosynthesis under K + starved conditions. Low chlorophyll content and poor chloroplast structure may also define photosynthetic processes and causes a decrease in crop growth and productivity under K + starvation. Under abiotic stresses such as drought, waterlogging, temperature, salinity, and heavy metal, the application of exogenous K + promotes plant tolerance by activating the antioxidant system, which limits the overproduction of reactive oxygen species (ROS), avoiding the associated oxidative damages where other signaling molecules such as nitric oxide (NO) and hydrogen sulfide (H 2 S) may involve. The review highlights the decisive role of exogenous and endogenous K + in modulating diverse physiological and biochemical processes in a healthy and stressful environment. Furthermore, this review appraises the involvement of K + with another signaling molecule in enhancing abiotic stress tolerance in plants. Therefore, this review provides a comprehensive update on the relevance of K + in higher plants. Its exogenous application should be a potential tool, especially in crops under adverse environmental conditions.