Tuesday, November 6, 2007 - 1:00 PM
191-1

Investigation of Na+- Induced Ca2+ Deficiency in Sugar Beet.

Abdul Wakeel, Diedrich Steffens, and Sven Schubert. Institute of Plant Nutrition, Justus Liebig University, Heinrich-Buff-Ring: 26-32, Giessen, 35392, Germany

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.