EFFECTS OF DRYING AND AGEING TREE LEAVES ON ABILITY OF THEIR AQUEOUS EXTRACTS TO DISSOLVE FERRIC OXIDE

The effect was studied of drying and ageing leaves on the ability of their water extracts to dissolve hydrous ferric oxide. Extracts of freshly collected picked and autumn‐fallen oak, beech, and larch leaves were compared with those of leaves from the same collections that were either freeze‐dried or dried at 105°C. The iron‐dissolving properties of the fallen leaves were not significantly affected by either method of drying, but drying at 105°C greatly increased the activities of picked larch and beech leaves. Freeze‐drying had relatively little effect. Larch needles lost their activity very quickly when aged aerobically for 8 months, while the activity of beech leaves decreased slowly. The activity of picked and fallen oak leaves increased dramatically during the first 1–2 weeks, and then decreased, rapidly at first; after 8 months the activity was still comparable with the initial value. There was no direct relationship between the activities of the extracts and the pH or the concentrations of polyphenols. Copyright © 1968, Wiley Blackwell. All rights reserved