Sodium-induced calcium deficiency in sugar beet during substitution of potassium by sodium

Abstract

Functions of sodium (Na+) and potassium (K+) are closely associated. In some crops, Na+ is able to prevent or reduce considerably the occurrence of K+ deficiency. Sugar beet (Beta vulgaris L) is a natrophilic crop, and positive effects of Na+ applications on yield were observed when K+ was sufficiently supplied. However, it is not known which specific function of K+ can limit the growth of sugar beet when K+ is substituted by an equivalent amount of Na+. Therefore, K+ substitution by Na+ was investigated for sugar beet in hydroponics. Surprisingly, no K+-deficiency symptoms were observed. However, calcium (Ca2+) concentrations in the leaves were significantly decreased. Moreover, Ca2+ uptake and translocation through xylem sap were reduced in Na+-treated plants. It is concluded that Ca2+ uptake by roots and its translocation via xylem sap primarily limit the possibility of K+ substitution by Na + in sugar beet nutrition. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.