Can Optimized Potassium Fertilization Enhance the Salt Stress Tolerance of Crops?

Salt (NaCl) affects more than 20 % of the world's irrigated land and causes huge economic losses by limiting agricultural production due to increased salinization. Soil salinization is a significant global problem that affects plant development through ion toxicity and nutrient imbalance. In plants, salt stress triggers two sequential responses. First, there is a rapid osmotic shock that reduces relative water content, leaf water potential, stomatal conductance, and turgor potential. After this first phase, a phase of ion homeostasis is induced, triggering salt toxicity and accelerating senescence of mature leaves.

Salt stress is induced by high concentrations of sodium (Na⁺) and chloride (Cl^-) in the soil. Excess Na⁺ and Cl^- ions compete with other nutrient elements and can lead to reduced nutrient uptake and translocation, and thus to imbalances in nutrient status. However, Na⁺ is not essential for plants. Potassium (K⁺) in particular is susceptible to this competition because of its similar chemical properties to Na⁺, for example, in ionic radius and hydration energy. K⁺ is an essential plant nutrient and is required for enzyme activity, energy transfer, protein synthesis, osmoregulation, stomatal movement, phloem transport, anion-cation balance, and stress resistance. K⁺ is particularly important as an inorganic osmotic element in plant cells, and therefore adequate K⁺ supply is critical for the regulation of turgor-controlled processes such as stomatal movement and cell elongation.

The interaction between Na⁺ and K⁺ can have negative effects on K⁺ uptake, which is regulated by passive and active transport systems. K⁺ is transported from roots to shoots by transpiration-driven water flux in the xylem, which is impaired during salt stress. Disruption of K⁺ homeostasis occurs, which is crucial for salt stress tolerance. For optimal plant growth, Na⁺ uptake must be reduced and K⁺ uptake increased, as a higher K⁺/Na⁺ ratio favors salt stress tolerance in plants.

The goal of this project is to gain insight into the importance of K⁺ in mitigating salt stress and to investigate the response of plants to salinity using different K⁺ supplies.