ABSTRACT
Many minerals, such as iron (Fe), zinc (Zn), manganese (Mn), nickel (Ni), and selenium (Se), are part of the essential micronutrient requirements of many organisms. Deficiencies in minerals are therefore generally detrimental for proper development, growth, and ability to withstand biotic and abiotic stresses. This chapter focuses on the possibilities of improving the bioavailable Fe and Zn status of crop products through biotechnology. To absorb and maintain a balance of potentially toxic metal ions, plants utilize poorly understood mechanisms involving a large number of membrane transporters and metal-binding proteins with overlapping substrate specificities and complex regulation. In general, plants acquire nearly all Fe and Zn through uptake via the roots. Zinc basically follows the same route as Fe in plant uptake and distribution; however, the genes involved are even less well known than for Fe.
