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Handbook of Plant Nutrition - chapter 11

11 Iron Julius von Sachs, the founder of modern water culture experiments, included iron in his first nutrient cultures in 1860, and Eusèbe Gris, in 1844, showed that iron was essential for curing chlorosis in vines. | CRC_DK2972_Ch011.qxd 7 1 2006 7 15 AM Page 329 11 Iron Volker Römheld University of Hohenheim Stuttgart Germany Miroslav Nikolic University of Belgrade Belgrade Serbia CONTENTS 11.1 Historical Information.329 11.1.1 Determination of Essentiality.329 11.2 Functions in Plants .330 11.3 Forms and Sources of Iron in Soils.330 11.4 Diagnosis of Iron Status in Plants.332 11.4.1 Iron Deficiency.332 11.4.2 Iron Toxicity.332 11.5 Iron Concentration in Crops.335 11.5.1 Plant Part and Growth Stage.335 11.5.2 Iron Requirement of Some Crops.335 11.5.3 Iron Levels in Plants.336 11.5.3.1 Iron Uptake.336 11.5.3.2 Movement of Iron within Plants.338 11.6 Factors Affecting Plant Uptake.339 11.6.1 Soil Factors.339 11.6.2 Plant Factors .343 11.7 Soil Testing for Iron .344 11.8 Fertilizers for Iron.344 References.345 11.1 HISTORICAL INFORMATION 11.1.1 Determination of Essentiality Julius von Sachs the founder of modern water culture experiments included iron in his first nutrient cultures in 1860 and Eusebe Gris in 1844 showed that iron was essential for curing chlorosis in vines 1 2 . Sachs had already shown that iron can be taken up by leaves and within a few years L. Rissmuller had demonstrated that foliar iron is obviously translocated by phloem out of leaves before leaf fall in European beech Fagus sylvatica L. . The early developments in the study of iron in plant nutrition were summarized by Molisch in 1892 3 . It was another 100 years before the principal processes of the mobilization of iron in the rhizosphere started to be understood 4-8 . 329 CRC_DK2972_Ch011.qxd 7 1 2006 7 15 AM Page 330 330 Handbook of Plant Nutrition 11.2 FUNCTIONS IN PLANTS The ability of iron to undergo a valence change is important in its functions Fe2 1 Fe3 electron It is also the case that iron easily forms complexes with various ligands and by this modulates its redox potential. Iron is a component of two major groups of proteins. These are the heme proteins and the Fe-S proteins. In these .