POTASSIUM. “Key metabolic processes in the cytoplasm such as enzymatic reactions, protein synthesis, and ribosome functions rely on K+ as a co-factor. An increased level of Na+ creates a competing environment for K+ binding sites and thus decreases efficiency of these processes. Moreover, detrimental effects can propagate from the cytoplasmic compartment into the chloroplasts, leading to a decreased efficiency of photosynthesis which in turn impairs growth.”
http://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-11-8