One of the most severe effects of salt stress is the absorption of Na+ ions by plant roots. High levels of external Na interfere with K acquisition by the roots, disrupt the integrity of root membranes and alter their selectivity that must be sufficient to meet the levels of K required for metabolic processes, for the regulation of ion transport, and for osmotic adjustment. Calcium is strongly a competitive with Mg+2 and the binding sites on the root plasma membrane appear to have less affinity for the highly hydrated Mg+2 than for Ca+2. Sodium chloride