Nitrate transfer and remobilization in leaves
Three nitrate transporters have been shown to be involved in nitrate
transfer and/or redistribution to the phloem from xylem or source
nitrate-containing tissues: NPF2.13/NRT1.7, NPF1.1/NRT1.12, and
NRT1.2/NRT1.11 (Iqbal et al., 2020). In particular, it has been recently
shown that NPF2.13/NRT1.7 is essential for remobilization of nitrate
from old leaves to deliver nitrate into the phloem, making it available
for new, developing leaves and enhancing nitrogen use efficiency (Chen,
Chen, Tseng, & Tsay, 2020). NPF1.1/NRT1.12 and NPF1.2/NRT1.11 have been
found to be involved in the transfer of xylem nitrate to phloem in the
petiole thereby facilitating nitrate remobilization from mature (old)
leaves to young leaves (Hsu & Tsay, 2013).