Nitrogen (N) is an essentially critical element which is involved in signalling and can affect plant growth and development. The plants have evolved different strategies involving short- and long-ranged signalling pathways to cope with the changes in N regulations in the soil. These pathways work at cell and plant level for coordination of N metabolism, growth, and development in accordance with the external and the internal N status. Currently, identification and characterization of local and systemic signalling has been emphasized, but information about integrating coordination and organization of N response of the plants is still lacking. Tracing out the full N pathway could help us to devise and produce high N-efficient genotypes and increase Nitrogen use efficiency (NUE). In this chapter, we discuss the physiological as well as molecular means to understand the mechanisms involved in local and systemic nitrogen responses and how these responses are coordinated.