As a mineral nutrition, most terres

As a mineral nutrition, most terrestrial organisms (fungi, bacteria and plants) rely on the uptake of inorganic ions from the soil or terrestrial environment. In the natural ecosystems, the availability of these ions dramatically fluctuates in both time and space, which makes nutrient-limiting conditions. To face this natural constraint, all organisms develop adaptive responses triggered by sensing systems that perceive external nutrient availability (Holsbeeks et al, 2004; Schachtman and Shin, 2007; Gojon et al, 2009). Plants are non-motile and therefore they have evolved a highly sophisticated and complex sensing and signaling mechanisms to respond to the dynamic changes of their surrounding environments. After carbon, hydrogen and oxygen, nitrogen (N) is one of the essential elements in plants due to its key role in chlorophyll production and is fundamental for the photosynthesis process. In addition, N is a part of various enzymatic proteins that catalyze and regulate plant-growth processes