Previous studies have
shown that short-term Fe-deficient treatments could stimulate
the activity of nitrate reductase (NR) in plants (Jin, Du, Shamsi,
Luo, & Lin, 2011). Reduction of nitrate to nitrite by NR is the limiting
step in the nitrate assimilation pathway in plants. Consequently,
the decrease of nitrate accumulation during mild Fedeficiency
may be attributed to the stimulation of NR activity.
However, because Fe is a cofactor of the NR enzyme, extreme Fedeficiency
may result in inhibition of NR activity, which is probably
the reason for high nitrate accumulation in the blades from the
0 lM FeEDTA treatment.