The Behaviour of Iron Chelating Agents with Plants

Abstract

The absorption by normal and iron-deficient bean plants of Fe and of ethylene-diamine-bis-(orthohydroxyphenylacetic acid) (EDHPA) is described; and the metabolism in plants of this chelating agent and of ethylenediaminetetra-acetic acid (EDTA) is examined using ¹⁴C-labelled compounds. Iron-deficient plants absorb Fe rapidly and preferentially, absorption of the chelate itself is slower but continuous. Normal plants absorb Fe and chelate in equimolar amounts. Bicarbonate ions in the culture solution inhibit the preferential absorption of Fe by iron-deficient plants, equimolar amounts of Fe and chelate being taken up. These results are discussed in relation to apparently conflicting reports on Fe and chelate uptake in the literature. The recovery of ¹⁴C from plants treated with ¹⁴C-labelled chelates does not reflect the true extent of the breakdown that has taken place: with both EDTA and EDHPA less than half the ¹⁴C recovered was as unchanged chelate.