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Investigations on the Mobilization and Transport of Iron in Forested Soils. II. The Nature of the Reaction of Leaf Extracts and Leachates with Iron¹

ABSTRACT

Electrodialysis of poplar leaf extracts enriched with iron indicated that the major part of the iron was present either as ferric hydroxide or in a form readily convertible to the latter. Interaction of such solutions with iron produced only a general increase in light absorption: no absorption maxima indicative of chelation were observed. The major part of the iron present in these enriched aqueous solutions could be recovered by extraction with 8-quinolinol in chloroform.

Fractions isolated from poplar leaf extracts and leachates by precipitation in 80% aqueous ethanol possessed the major part of the capacities of these solutions to react with iron. Evidence was obtained that the principal component of these active fractions had the characteristics of an acidic polysaccharide. Potentiometric titrations of these active fractions in presence and absence of ferric ions failed to reveal evidence of chelation.

It is concluded that both the forest canopy and the forest floor contribute solutions capable of the mobilization and transport of iron, and conclusions are drawn relative to the conditions favourable to such action of these solutions.

¹ Contribution from the Faculty of Agriculture, McGill University, Macdonald College, Que., and the Canada Experimental Farms Service, Macdonald College Journal Series No. 372.

² Post-graduate Research Assistant, and Professor of Chemistry.

Received for publication October 11, 1954.