Physiological Disorders of the Nicotianamine-auxothroph Tomato Mutant chloronerva at Different Levels of Iron Nutrition II. Iron Deficiency Response and Heavy Metal Metabolism

Summary The tomato mutant chloronerva exhibits typical symptoms of iron deficiency. Iron deficiencyinduced proton secretion occurs up to 10 µM FeEDTA in the nutrient medium (wild-type only at iron supply lower than 1 µM). Thickened root tips and root hair zones are formed up to 20 µM Fe (wild-type root hairs up to 5 µM). The ferric reductase activity of the rhizodermis remains higher than in the wildtype up to 100 µM Fe supply. In the concentration range of 5 to 10 µM Fe supply the mutant accumulates the 2- to 3-fold amount of iron in the shoot compared with the wild-type. The increased uptake of certain heavy metals (e. g. Cu, Mn, Zn) by the wild-type under iron deficiency is extended to a higher iron supply range in the mutant. All these deviations from the wild-type behaviour are overcome by the supply with nicotianamine (NA) to the leaves. The role of NA as an intracellular transporter for Fe(II) in the regulation of iron metabolism and iron deficiency response mechanisms is discussed.