NO2-drived NO3– metabolism in leaves

Atmospheric nitrogen dioxide (NO2) can be dry/wet deposited into plant leaves mainly through stomata, with a small fraction of cuticle deposition. Plants in nature present a wide variation in NO2 assimilation and the resistance. The ability of leaf NO2 uptake and efficient remobilization of NO2-derived NO3–/NO2– is important for normal plant growth and to withstand nitrogen deprivation. Moreover, leaf- and root-derived NO3– metabolisms have both links and differences. This review emphasizes on the fates of NO2-drived NO3–, including i) the assimilation into amino acids, ii) accumulation in vacuoles, and iii) reemission by NOx (NO and/or NO2), and discuss metabolic differences of NO2-drived and root-derived NO3–. Special attention is drawn to NOx evolution in apoplast and symplast of leaves and its control to stomatal dynamics. Moreover, further progress is proposed to get a better understanding of the dynamic uptake of NO2 and NO3– transporters in leaves.