Nutrient uptake by roots is related to mineral nutrition, which includes the supply, absorption, and utilization of nutrients essential for the growth and yield of crop plants (Fageria and Oliveira, in press). Mineral nutrition alone has contributed signi‰cantly to increased crop yields during the twentieth century. Borlaug and Dowswell (1994) reported that 50% of the increase in crop yields worldwide during the twentieth century was due to the application of chemical fertilizers. The authors also reported that during the twenty-‰rst century, the essential plant nutrients would be the single most important factor limiting crop yields, especially in developing countries. Borlaug and Dowswell (1997) state that science-based commercial agriculture is more of a twentieth-century invention. Loneragan (1997) states that knowledge generated during the twentieth century in the ‰eld of mineral nutrition has had an impact on current food production and provided information needed for further advances for the twenty-‰rst century. Nutrient uptake is regulated by growth rate and nutrient availability. Actively growing plants usually exhibit a high nutrient uptake rate in order to meet demands for optimum growth (Marin et al., 2011). Optimum growth is a result of high carbon ‰xation in the leaves, which in turn supplies the roots with carbohydrates and energy for nutrient uptake. Internal nutritional status may also regulate uptake rate by the synthesis of signal molecules that are transported from the shoot to the root (Marin et al., 2011).