POLYPHENOLS IN PLANT, HUMUS, AND SOIL

Abstract

Summary The two pure polyphenols, D‐ and epi ‐catechin, known to be present in the fresh green leaves of a number of tree species, have been shown to be capable of reducing ferric iron, in the form of hydrated ferric oxide, to an organic ferrous complex and solubilizing it in much the same way as do Bloomfield's leaf extracts. These polyphenols can remove iron, even when held firmly as in Triassic sand, and transport it as ferrous iron at low pH. Model soils, consisting of alumina and diatomaceous earth impregnated with ferric chloride, were treated with catechin solutions and fresh green‐leaf extracts. Both produced dark coloured bands in which substantial amounts of ferric iron had been converted to ferrous iron. Extracts of green beech leaves from a mor site were more effective than those from a mull site (June leaf collection). Extracts of humus and litter were singularly low in reducing and iron‐complex‐forming substances, corresponding to their low free polyphenol status. The illuvial horizon of a podzol formed on Barton sand has yielded organic matter on extraction with acetyl acetone. This contained much material of polyphenol origin associated with iron. The role of polyphenol activity towards iron is discussed in relation to podzolic and other soils.