Nitrate modifies the assimilation pattern of ammonium and urea in wheat seedlings

Abstract

These results suggest that the effect of nitrate is compatible with a rapid and transient increase in the activity of glutamine synthetase and urease during the first hour after the onset of treatments. Nevertheless, a possible effect of nitrate reducing ammonium accumulation through the activation of alternative metabolic pathways different from that involving glutamine synthetase cannot be ruled out. Finally, nitrate effects on amino acid concentration indicate that, whereas ammonium assimilation takes place principally in the root, urea and nitrate assimilation occurred in the shoot, under the conditions of the experiment.

The signal effect of nitrate supply enhances active forms of cytokinins and indole acetic content and reduces abscisic acid in wheat plants grown with ammonium

“…However, the mechanisms responsible for these effects of NO 3 − remain unclear. Previous studies have shown that the presence of NO 3 − can alleviate these symptoms by increasing NH 4 + and urea assimilation, avoiding its accumulation (Garnica et al, 2010). On the other hand, several authors have suggested that the reduction in plant growth caused by strict NH 4 + nutrition is related to the accumulation of free putrescine, principally in the leaves (Houdusse et al, 2005;Belastegui-Macadam et al, 2007).…”

Do plants need nitrate? The mechanisms by which nitrogen form affects plants

“…Synthesis of NiR is regulated by a NO 3 − responsive cis ‐element (Konishi & Yanagisawa, ) but there is no evidence of post‐translational modification (Campbell, ). Generally, NR and NiR are substrate and light induced enzymes (Lillo, ), although there are high levels of constitutive NR in the leaves of some members of the Phaseoleae (Andrews et al ., ) and on rare occasions, NR is induced by NH 4 + or urea (Bungard et al ., ; Matraszek, ; Garnica et al ., ).…”

Both Free Indole-3-Acetic Acid and Photosynthetic Performance are Important Players in the Response of Medicago truncatula to Urea and Ammonium Nutrition Under Axenic Conditions

“…Additionally, the presence of nitrifying microorganisms, such as Nitrosomonas and Nitrobacter species, can lead to differential production of NO (Hollocher, 1981 ; Ferguson et al, 2007 ). This NO production often contributes positively to plants, as low NO contents in ammonium-containing media can trigger positive signaling effects on plants and, hence, reduce NH stress (Houdusse et al, 2005 ; Garnica et al, 2010 ; Hachiya et al, 2012 ). Moreover, soil microorganisms have been demonstrated to act as hormone producers, especially for auxins, gibberellins, cytokinins, and abscisic acid (Reddy and Saravanan, 2013 ).…”