Short term transport of iron and copper to various parts of wheat grains

Abstract

Increasing the micronutrient content of staple foods such as cereal grains is a way of addressing micronutrient deficiencies in humans. This strategy will only be successful if the micronutrients are distributed in parts of the grain that are generally consumed (i.e. the endosperm). To date there are limited reports of micronutrient distribution within wheat grains with most simply reporting content of the whole grain. We investigated the transport of radioactively labelled iron and copper into the grain of cultured wheat ears 18–22 days post anthesis. Ears were loaded for 24 hours and then the grains dissected into various components. The grains were dissected into: epidermis; percarp-testa (combined hypodermis/cross cells/tube cells/testa/nucellar layer); outer endosperm (with aleurone layer attached); central endosperm; embryo; combined tissues of the crease. The majority of the iron was transported into the endosperm (61%), followed by the crease (15%). The majority of the copper was found in the crease (51%) followed by the endosperm (24%). Samples taken from the inner part of the endosperm contained no detectable iron or copper suggesting that the iron and copper present in the endosperm was found in the aleurone layer. If these grains were milled industrially for white flour then most of the iron and copper in the grain would be lost. Although these measurements were short term, they reinforce the point that strategies to increase iron and copper transport into wheat grains must keep in view the destinations of iron and copper within the grain.