NH4+ toxicity in higher plants: a critical review

Britto, Dev T.; Kronzucker, Herbert J.

doi:10.1078/0176-1617-0774

Cited by 1,520 publications

(1,289 citation statements)

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“…Ammonium is in contrast to the situation in animal cells (e. g. see [22]) and plants (e.g., [4,5]) not toxic for the studied model bacteria C. glutamicum, E. coli, and B. subtilis, even in molar concentrations. Because most bacteria prefer ammonium as nitrogen source and some species even produce ammonium, for example, rhizobia and cyanobacteria by N 2 -fixation and proteolytic clostridia by amino acid fermentation, we assume that ammonium resistance is a general phenomenon in bacteria.…”

Section: Discussionmentioning

confidence: 66%

Ammonium Toxicity in Bacteria

et al. 2006

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Abstract. Although an excellent nitrogen source for most bacteria, ammonium was-in analogy to plant and animal systems-assumed be detrimental to bacteria when present in high concentrations. In this study, we examined the effect of molar ammonium concentrations on different model bacteria, namely, Corynebacterium glutamicum, Escherichia coli, and Bacillus subtilis. The studied bacteria are highly resistant to ammonium. When growth was impaired upon addition of molar (NH 4 ) 2 SO 4 concentrations, this was not caused by an ammonium-specific effect but was due to an enhanced osmolarity or increased ionic strength of the medium. Therefore, it was concluded that ammonium is not detrimental to C. glutamicum and other bacteria even when present in molar concentrations.Ammonium (in this communication, the term ''ammonium'' is used in a general sense, including NH 4 + and NH 3 ; distinct ammonium species are indicated by chemical formula) is the preferred nitrogen source for most bacteria and fungi, and also plants acquire ammonium as a nitrogen source from the soil [35]. When present in high concentrations, diffusion of NH 3 , which is in equilibrium with NH 4 + , across the cytoplasmic membrane into the cell is sufficient to promote growth. In a situation of ammonium limitation, diffusion becomes negligible and special carriers are synthesized in bacteria, fungi, and plants (for a recent review, see [36]).However, ammonium is a paradoxical nutrient, because it is notorious for its cytotoxic effects. Furthermore, active transport of ammonium can to lead to a harmful energy-wasting futile cycling when accumulated ammonium diffuses across the cytoplasmic membrane back into the medium. Sensitivity to ammonium is discussed to be a universal phenomenon; however, it is well investigated only in plant and animal systems [36], whereas the situation in bacteria is less clear.

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Section: Discussionmentioning

confidence: 66%

Ammonium Toxicity in Bacteria

et al. 2006

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“…Ammonium nutrition decreases essential cations content (Britto and Kronzucker, 2002), probably due to competition with NH 4 + in the uptake process. Although the uptake of cations other than NH 4 + is sometimes reduced, NH 4 + uptake usually increases under NH 4 + nutrition.…”

Section: Discussionmentioning

confidence: 99%

“…NH 4 + is a paradoxical nutrient ion because, despite being a major N source and an important intermediate in many metabolic reactions, there are reports that high concentrations of this ion in either soil or the nutrient solution may lead to an "ammonium syndrome". This may include leaf chlorosis, lower plant yield production and root/shoot ratio, lower cation content, acidification of the rizosphere and changes in several metabolites levels, such as amino acids or organic acids (Britto and Kronzucker, 2002). In spite of the information available about the appearance of toxic symptoms due to NH 4 + nutrition, different studies have produced contradictory results.…”

Section: Introductionmentioning

confidence: 99%

Ammonium enhances resistance to salinity stress in citrus plants

Fernández-Crespo

Camañes

García‐Agustín

2012

Journal of Plant Physiology

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In this work, we demonstrate that NH 4 + nutrition in citrange Carrizo plants acts as an inducer of resistance against salinity conditions. We investigated its mode of action and provide evidence that NH 4 + confers resistance by priming abscisic acid and polyamines, just as enhancing H 2 O 2 and proline basal content. Moreover it observed a diminished Cl -uptake as well as an enhanced PHGPx expression after salt stress. Control and N-NH 4 + plants have shown optimal growth, however it was observed that N-NH 4 + plants have displayed greater dry weight and total lateral roots than control plants, but that differences are not seen for primary roots length. Our results reveal that N-NH 4 + treatment induces a similar phenotypical response to the recent stress-induced morphogenetic response (SIMRs). The hypothesis is that N-NH 4 + treatment triggers mild chronic stress in citrange Carrizo plants, which might explain the SIMR observed. Moreover, we observed modulators of stress signaling, such as H 2 O 2 in N-NH 4 + plants, which could acts as an intermediary between stress and the development of the SIMR phenotype. This observation suggests that NH 4 + treatments induce a mild stress condition that primes the citrange Carrizo defense response by stress imprinting and confers protection against a subsequent salt stress.

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“…However, many plants develop toxic symptoms when ammonium is in excess. 1 Although rice is an ammoniumtolerant species, roots exhibit attenuated growth and tip coiling when exposed to high concentrations of ammonium in growth media. 2 idd10 mutant plants exhibit an ammonium-hypersensitive root phenotype.…”

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confidence: 99%