The relationship between nitrate transport and utilization in crop and nitrogen utilization efficiency

Objectives Ammonia (NH₄⁺) and nitrate (NO₃^-) are the primary forms for crop nitrogen (N) absorption and utilization. NO₃^- accumulation and utilization in plant tissues of dry land crops are the main components of N nutrient study, which are related to the NO₃^- content and N utilization efficiency (NUE) in plant tissues.

Main advances Absorbed NO₃^- in crop can be assimilated into organic N directly, secreted to the root, accumulated into vacuolar space and transported from roots to shoots. NO₃^- utilization efficiency and NUE were regulated by NO₃^- short distribution (vacuole NO₃^- distribution) and NO₃^- long transportation (between roots and shoots). Vacuole NO₃^- can not be assimilated into organic N, but the NO₃^- outside of the vacuole in protoplast can be utilized by crop directly. The higher proportion of NO₃^- in shoots has higher NUE, because the NO₃^- assimilation in shoots will take full advantage of the solar energy. In addition, NO₃^- is separated by vacuole, NO₃^- assimilation genes (NR) and transportation genes (NRT1.5and NRT1.8for long transport of NO₃^-) can not be induced by vacuole NO₃^-, but can be stimulated by the cytosolic NO₃^-. Consequently, not only NO₃^- assimilation is regulated by NO₃^- short distribution, but also affected the NO₃^- long transport between roots and shoots.

Prospective We summarized the mechanisms of NO₃^- short distribution and long transportation in this review, and provided some implications for further study on the relationship between NO₃^- long transportation and vacuole NO₃^- short distribution, and the response of crop NUE to NO₃^- transportation and utilization.