ABSTRACT
Supplying plants with inorganic nutrients is one of the major functions of roots. The ability of the roots to fulfil this function depends on two complex phenomena: nutrient availability in soil and nutrient acquisition by plants. The term nutrient availability summarizes the soil properties affecting nutrient supply to the plants, and it comprises two aspects: a chemical one and a positional one. The chemical aspect depends on the chemical bonds between the element and other ions or the soil matrix, and the concentration of the element in the soil. The positional aspect is related to both the distribution of the element in the rooting volume and its mobility in the soil. Mobility determines the rate of ion transport, and thus the amount of and the distance from which the ion can move through the soil toward the surface of a root. The term nutrient acquisition encompasses the plant properties that take part in nutrient supply to the plants. This phenomenon includes the physiological processes that are responsible for nutrient entry into the plant (see also Chapters 34 by Glass and 37 by Silberbush in this volume). Nutrient acquisition from a given soil may vary according to genus, species, or even variety. In many soils nutrient availability is inadequate for crop growth unless fertilized. Because of their importance for plant production, both phenomena have been studied intensively (for overview see Barber, 1995; Marschner, 1995; Tinker and Nye, 2000).
