What is the difference between nitrate and ammonia

The interactions between nitrate and ammonium should optimize N utilization in the field, where nitrate and ammonium often coexist and are found at various concentrations within short distances Lark et al. This review aims to summarize their interactions in physiological processes, focusing on N uptake, translocation, assimilation, and signaling. For molecular and physiological responses to either nitrate or ammonium, readers are also referred to previously published reviews by Nacry et al.

The interaction between nitrate and glutamate on root growth has been well documented in previous reviews by Forde and Walch-Liu , and Forde a , b. The physiological and molecular links between potassium and N sources nitrate and ammonium have also been discussed in detail by Coskun et al. In addition, recent advances regarding the mechanisms of toxicity of excessive ammonium in comparison with nitrate have been published by Li et al.

In the field, N availability often limits plant productivity, and hence uptake for N acquisition has attracted considerable research interest. Most plants benefit from a mixture of nitrate and ammonium in order to increase their N contents Miller and Cramer, ; Hachiya et al.

Thus, it is crucial that we understand how nitrate and ammonium interact with each other and how this affects N uptake at physiological, morphological, and molecular levels. The net N influx via roots consists of two components, total N influx and total N efflux Glass et al. The total efflux components include simple N leakage and those mediated by specific transporters and channels that facilitate N efflux Segonzac et al.

Kronzucker and co-workers determined the reciprocal effects of nitrate and ammonium on the components of N flux in rice and barley roots using a highly sensitive 13 N-labeled radiotracer. They found that net nitrate uptake was significantly inhibited by the co-provision of ammonium, as compared to that observed with nitrate alone Kronzucker et al.

The total nitrate influx followed the same tendency as the net nitrate influx, whereas the efflux rates were either decreased or not changed by ammonium. Thus, decreases in the net nitrate influx were determined by the total influx component. In barley, inhibition of total nitrate uptake by 1 mM ammonium was significant under low nitrate conditions below 1 mM , suggesting the involvement of the high-affinity transport system HATS Kronzucker et al.

Levels of the AtNRT2. Some of the underlying molecular mechanisms have been identified. The ammonium-dependent repression of AtNRT2. This observation seems reasonable given that AtNRT2. The results of a split-root experiment indicated that the nitrate concentration i.

This local effect of nitrate is mediated by AtNRT1. In AtNPF6. Nitrate transport and signaling via AtNPF6. The existence of phosphomimic AtNPF6. Widiez et al. This gene product leads to trimethylation of histone H3 lysine 27 at the NRT2. Taken together, the evidence suggests that ammonium-dependent repression of nitrate uptake occurs through the convergence of nitrate- and ammonium-dependent mechanisms.

Experiments utilizing the 13 N radiotracer technique have demonstrated that, in rice, net ammonium uptake becomes higher with the co-provision of nitrate, compared with ammonium alone Kronzucker et al. Using the microelectrode technique, a similar facilitating effect of nitrate on net ammonium uptake was confirmed in Brassica napus and Populus popularis roots Babourina et al.

In rice, increased total ammonium uptake and decreased total ammonium efflux concomitantly contribute to the enhanced net ammonium uptake in the presence of nitrate Kronzucker et al. However, it remains unknown how nitrate facilitates the net ammonium uptake. When ammonium is the sole N source, a major ammonium transporter, AtAMT1;1, is inactivated via phosphorylation, which limits the ammonium influx Engelsberger and Schulze, It is unknown whether the co-provision of nitrate and ammonium could restore the activity of AtAMT1;1 via dephosphorylation.

At higher concentrations of ammonium, gaseous ammonia transport via the aquaporins represents an indispensable component of influx at the plasma membrane in barley roots Ariz et al. This implies that aquaporins are involved in the nitrate-dependent enhancement of total ammonium uptake, although aquaporins also facilitate the total ammonium efflux Coskun et al.

The enhancement of net ammonium uptake by the coexistence of nitrate can overcome the repressive effects of ammonium on net nitrate uptake, which results in improved N acquisition under the application of both nitrate and ammonium, as compared to that with nitrate or ammonium alone Kronzucker et al.

This phenomenon is worthy of attention as a potential target to improve N acquisition. Components of the influx and efflux of nitrate and ammonium in roots.

Under acidic pH, microbial nitrification is suppressed, resulting in an accumulation of ammonium and a lowering of nitrate in the soil. The diffusion coefficients of nitrate and ammonium in water are similar. However, nitrate and ammonium ions differ in their behavior in soil water, because the soil has complex properties, including its negative ion charge and viscosity Miller and Cramer, The diffusion coefficient of nitrate is estimated to be 10—fold higher than that of ammonium in certain soil waters.

Plants are required to adapt their root morphology in response to nitrate or ammonium in order to optimize N absorption from the soil. Hence, the morphological responses of LRs to nitrate and ammonium have been documented with particular interest in A. Overall, application of ammonium stimulates LR branching, whereas nitrate stimulates LR elongation. Interestingly, application of nitrate and ammonium together enhances branching and elongation of LRs concomitantly, suggesting that the application of nitrate and ammonium has local, complementary effects on LR development.

Lima et al. For example, finely branched LRs are efficient at absorbing ammonium fixed on the soil surface, whereas longer LRs can explore highly mobile nitrate sources. These independent responses to local nitrate and ammonium are dependent on a nitrate transporter, AtNPF6.

Since AtNPF6. The transceptors allow plant roots to forage N-rich patches with an adequate morphology, optimizing N acquisition from heterogenous N conditions. Root hairs increase the surface area of roots and enhance their ability to uptake N. However, few studies have analyzed the root-hair responses to different N sources. Both the density and average length of root hairs are increased by a decrease in N availability in some grass species and vegetables Foehse and Jungk, ; Robinson and Rorison, Interestingly, cell-specific transcriptome analysis in A.

Thus, the extracellular environments are alkalinized and acidified following the application of nitrate and ammonium, respectively Escobar et al. The microbial conversion of ammonium to nitrate i. Notably, acidic conditions induce AtNPF6. Under nitrate conditions, AtNPF6. This observation suggests that acidic induction of AtNPF6. Expression of AtSLAH3 is increased under conditions of acidic pH, which facilitates nitrate efflux without being accompanied by proton export.

Thus, NPF6. A recent study has demonstrated that OsNRT2. Interestingly, overexpression of this gene enhances nitrate uptake in the presence of nitrate alone, but represses it under a mixture of nitrate and ammonium. There are two alternative fates of nitrate following its absorption from the soil. One involves immediate nitrate reduction in the roots, and the other involves root-to-shoot transport via the xylem followed by nitrate reduction in the leaves. In herbal species, most of the nitrate is reduced predominantly in the shoots via the reducing equivalents derived from photosynthesis Scheurwater et al.

Low-affinity nitrate transporters AtNRT1. There proteins are expressed in the pericycle cells of roots, and loss-of-function mutants have been shown to decrease the root-to-shoot nitrate transport. Nitrate transported to the shoots via the transpiration stream is imported to the petiole for nitrate storage by AtNRT1. A high proportion of moderate-concentration ammonium is assimilated in the roots. Cytosolic isoforms of glutamine synthetase GS , AtGLN1;2, and OsGS1;2 are expressed largely in roots, are induced by ammonium, and contribute to primary ammonium assimilation in the roots Ishiyama et al.

AtGLN1;2 is localized in the endodermis and vasculature of roots Guan et al. Thus, with relatively lower concentrations of ammonium e. When the root GS capacity is exceeded by a large amount of ammonium, it can be directly loaded into the xylem Husted et al. The molecular mechanisms responsible for xylem loading of ammonium remain unknown. In barley seedlings, the addition of 10 mM ammonium significantly inhibits the xylem loading of potassium, whereas equimolar nitrate has little effect Kronzucker et al.

Ammonium delivered to the shoots will flow directly out to the apoplast, because the ammonium concentrations in the xylem sap are similar to those in the apoplast in barley Schjoerring et al. Ammonium is preferentially distributed to younger leaves compared with older leaves, implying that ammonium distribution might be under the control of transpiration Kiyomiya et al. Kiyomiya et al. A possible explanation is that the enhancement of net ammonium uptake by nitrate in roots can increase the amount of N loaded into the xylem.

Kronzucker et al. Interestingly, they found that in the presence of nitrate, a larger proportion of the isotopic signal was allocated to the xylem compared with that observed in the presence of ammonium only.

It should be noted that these analyses do not clarify the molecular identity of the N compound in xylem. However, in the rice examined by Kronzucker et al.

Plants of A. Interestingly, in barley grown with nitrate and ammonium, the addition of potassium reduces ammonium accumulation in the shoots more effectively than in the roots ten Hoopen et al.

AtSKOR might be involved in the root-to-shoot transport of ammonium under both nitrate and ammonium conditions. The N source is also known to be a determinant of apoplastic pH. In ryegrass, switching the root N source from 3 mM nitrate to ammonium causes a rapid increase in the ammonium concentration in the leaf apoplast and a concomitant decrease in apoplastic pH Schjoerring et al.

Perfusion experiments utilizing petioles of detached sunflower leaves revealed that nitrate application increases apoplastic pH, whereas ammonium decreases it, as observed in the rhizosphere Hoffmann et al. Within 12 h of treatment, there is a significant difference of 0. The simultaneous application of nitrate and ammonium results in an intermediate pH value, suggesting that these N species act on apoplastic pH independently.

Notably, in detached leaves of Commelina communis , the sensitivity of the stomatal response to ABA is increased with nitrate application, and decreased in response to ammonium Jia and Davies, Since ABA is a weak acid pK a 4. Protonated ABA with no ionic charge diffuses into the cells through the plasma membrane. Thus, the apoplastic pH is a determinant of the cellular compartment of ABA. It has been demonstrated that AtNPF4.

Additionally, indoleacetic acid IAA is a phytohormone with a pK a of 4. Several reports have shown that apoplastic pH can alter IAA import to the cytosol, which regulates organ development and guard-cell movement in A. A nitrate transceptor, AtNPF6. Independently of this direct link between nitrate and auxin uptake, AtNPF6. Local changes in pH associated with N transport represent a missing link in our understanding of the different responses to nitrate and ammonium.

In herbal species grown under moderate N concentrations, nitrate and ammonium are assimilated mainly in shoots and roots, respectively see above. Under conditions of abundant N supply, which is often the case in cultivated fields, nitrate and ammonium are likely to be processed in the same organs Guan et al.

N assimilation requires the reducing equivalents and carbon skeletons that are derived from carbon metabolism. Masakapalli et al. Supplementation with ammonium significantly redirects carbon fluxes Fig. The first important change is a decreased flux through the oxidative pentose phosphate pathway oxPPP in the presence of ammonium [see a in Fig.

Nitrate reduction from nitrate to ammonium via nitrite is the second largest sink for reducing equivalents following carbon fixation Noctor and Foyer, The coexistence of ammonium with nitrate suppresses nitrate uptake, thereby decreasing the relative demand on NADPH for nitrite reduction.

The second notable finding is the increased glycolytic production of pyruvate through pyruvate kinase PK and fluxes via the tricarboxylic acid TCA cycle in response to ammonium application [see b in Fig. Thus, the ammonium-dependent enhancement of C input to the TCA cycle is associated with increased N assimilation, which is supported by the higher levels of amino acids and proteins observed when both ammonium and nitrate are present compared with nitrate alone in A.

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Ammonium nitrate can also be used as a good plant fertilizer; however it is far better suited to controlling acidic soil. The nitrate compound is also used in the production of cold packs; when the substance is added to water it creates an endothermic chemical reaction.

The surrounding heat is absorbed into the mixture, turning the product extremely cold. The greatest difference between the two chemical compounds is quite terrifying.

Ammonium nitrate can be used as an explosive; when the granules are mixed with a fuel like diesel, an explosive mixture is created. Both compounds make good plant fertilizers; ammonium nitrate for acidic soil and ammonium sulphate for alkaline soil, 4.

Making ammonium nitrate is an extremely dangerous process and must only be performed by industrial professionals. Ammonium sulphate is a natural occurring substance that is commonly recreated in an industrial process. Ammonium nitrate can be used to create an explosive substance when mixed with alcohol. Ammonium sulphate is a safe compound that can even be used as a food additive. Difference Between Similar Terms and Objects.

We will be discussing the major differences between ammonia and ammonium nitrate in this article. Overview and Key Difference 2. What is Ammonia 3. What is Ammonium Nitrate 4. Ammonia is an inorganic chemical compound having the chemical formula NH 3. It exists in the gaseous state at room temperature and pressure. Thus, it is colourless and has a pungent, irritating odour. Moreover, it is considered commonly as a nitrogenous-waste, mainly among aquatic organisms.

Likewise, it is an alkaline compound.