Differential Absorption of Metal Chelate Components by Plant Roots

Abstract

Exudates from groups of zinnia, sunflower, and soybean plants with roots in ethylenediamine di(o-hydroxyphenylacetic acid) (EDDHA) contained small quantities of EDDHA. Exudate from plants with roots in the iron chelate, FeEDDHA, contained small amounts of FeEDDHA and large amounts of total Fe. Exudate collected at time intervals from sunflower plants with roots in FeEDDHA showed high concentrations of Fe in the exudate. Samples of nutrient solution collected at the same intervals revealed a progressive loss of Fe and a concomitant increase in chelating capacity. The addition of excess Fe+++ to the nutrient proved that iron-free EDDHA had accumulated in the nutrient solution when Fe was released to the roots. It is concluded that the roots of plants can extract Fe from a chelate and leave the chelating agent in the nutrient medium.