Distribution and remobilization of iron and copper in wheat.

The amount of iron (Fe) and copper (Cu) that is loaded into grains of wheat (Triticum aestivum) depends on both the amount of nutrient taken up by the plant post-anthesis and the amount that is remobilized from vegetative organs as they senesce. Previous reports have shown that these two micronutrients behave quite differently in wheat in that Cu is readily remobilized to the grain whilst Fe shows poor remobilization. The object was to quantify the distribution of Fe and Cu in wheat and to show how this distribution changes from anthesis to grain maturity. The uptake and distribution of both Fe and Cu were investigated in wheat grown at two levels, adequate and low, of both micronutrients. Plants were grown in sand culture and the main culms were harvested at anthesis, 18 days post-anthesis and at maturity. Plants were separated into various organs and analysed for Fe and Cu using ICP-OES. There was good remobilization of Fe from the rest of the shoot to the grain with 77 % of the total shoot Fe in the grain at maturity. In the adequate-Cu treatment there was 62 % of the total plant Cu in the grain at maturity, whereas in the low-Cu treatment this was only 40 %. There was no net Fe taken up into the above-ground plant parts post-anthesis whilst for Cu there was. The remobilization evident for Fe and Cu was greater than that found for zinc and much greater than evident for manganese in the same material. The results reported here represent good evidence for the high reproductive mobility of both Fe and Cu in wheat.