Abstract:Nitrate (NO3-) is the main source of inorganic nitrogen for plants in aerobic soil conditions. Adequate supply of nitrate is necessary for good plant growth. Plant lateral root development can show morphological plasticity in response to the heterogeneous supply of soil nitrate. In barley, Arabidopsis thaliana and maize, the effects of the nitrate supply on root growth and development have been identified. These are a localized stimulatory effect of external nitrate on lateral root elongation and a systemic inhibitory effect of high tissue nitrate concentrations on lateral root growth. A review is given on the study progress of the mechanisms underlying plant lateral root development under different concentrations of nitrate. Several sensing and signaling pathways are involved in root nitrate responses in Arabidopsis thaliana. The MADS-box transcription factor ARABIDOPSIS NITRATE-REGULATED1 (ANR1) is associated with external nitrate abundance. Nitrate transporters such as o NRT1.1 and NRT2.1 may also be components of signaling pathways. Systemic inhibition of LR development has been linked to abscisic acid. Long-distance signals mediating the shoot response to nitrate perception in roots may also involve auxin signalings. MicroRNAs have also been shown to modulate LR emergence in response to nitrate.