Physiological actions of Na⁺ and K⁺ in plant metabolism are closely associated and studies have shown that in some crops Na⁺ is able to prevent or reduce considerably the occurrence of K⁺ deficiency. Sugar beet (Beta vulgaris L.) is an important crop due to its ability to store sucrose in high concentration in its root. It is a natrophilic crop and positive effects of Na⁺ applications on yield have been observed when K⁺ was sufficiently supplied. In previous studies, while studying equivalent substitution of K⁺ by Na⁺ in sugar beet nutrition, neither potassium deficiency symptoms were observed nor plant growth was affected. However, calcium deficiency symptoms were noticed when Na⁺ was applied. In that study Ca²⁺ concentration in the beets was unaffected while in leaves it was significantly reduced. Assumedly, Na⁺ hinders Ca²⁺ either in non-selective cation channels (NSCC) in root epidermal cells or outward-rectifying cation channels (ORCC) in stelar parenchyma cells. To investigate the above assumption nutrient solution experiments were conducted in a growth chamber where plants were supplied either with K⁺ or with an equivalent amount of Na⁺ after establishing seedling with full nutrient solution containing K⁺. Plant growth, ion interaction and translocation of Ca²⁺ through xylem sap were studied. It was found that plant growth has not been affected; even fresh weight of shoot and root was increased in some cases when K⁺ was substituted by Na⁺. However, cation concentrations in the plants were disturbed. Potassium concentration was reduced and Na⁺ was increased in the root and shoot and Ca²⁺ was reduced significantly when K⁺ was replaced by Na⁺. Furthermore Ca²⁺ uptake was reduced significantly in young leaves, when plants were supplied with Na⁺. The data from these experiments suggest that uptake of Ca²⁺ is decreased by substituting with equivalent amount of Na⁺. Possible reasons for the hindrance in Ca²⁺ uptake due to application of Na⁺ will be discussed in the presentation.