Effect of EDTA on transport forms of manganese in maize xylem exudate

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Abstract
Xylem exudates were collected from 20-day-old maize seedlings grown for 24 h in labelled manganese chloride solution (10 ppm) with or without EDTA (18 mgl-1). The distribution of radioactivity on paper ohromatograms of exudates did not show the existence of free Mn. Fractionation of exudate constituents by gel filtration on Sephadex G-26 showed that54Mn is associated with three UV (254 nm) -absorbing fractions. Two fractions contain amino acids (M. wt.:≧ 10 000 and ∼ 900). The third fraction (M. wt. ∼ 600) however, appears to be a carrier of a different type, which is practically amino acid free, although it contains 10.23% N (by elementary analysis). The properties of this carrier are discussed. Application of EDTA has favoured the; transport of Mn in xylem sap with fractions of relatively lower molecular weights.