Nitrogen Assimilation and the Control of Ammonium and Nitrate Absorption by Maize Roots

Lee, R. B.; Purves, Judith V.; Ratcliffe, George; Saker, L. R.

doi:10.1093/jxb/43.11.1385

Cited by 165 publications

(113 citation statements)

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“…Inhibition of nitrate uptake by ammonium is well described in woody species (Serna et al 1992;Kreuzwieser et al 1997;Gessler et al 1998). Some research considered that the products of nitrate and ammonium assimilation resulted in the inhibition, because the products, such as amino acids, were responsible for the down-regulation of nitrate uptake when ammonium is supplied simultaneously (Lee et al 1992;Imsande and Touraine 1994). After uptake, ammonium is assimilated mainly in the roots, while the NO 3 -is assimilated in both roots and shoots of plants (Andrews 1986;Munzarova et al 2006), and the ammonium can be converted into amino acids directly, whereas NO 3 -needs to be reduced to NH 4…”

Section: Sex-specific Difference Of Biomass Accumulation and Allocationmentioning

confidence: 99%

Populus deltoides females are more selective in nitrogen assimilation than males under different nitrogen forms supply

Dong

Guo

et al. 2014

Trees

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Key Message Female cuttings of Populus deltoides were sensitive to inorganic nitrogen forms and biased for NO 3 2 -N, whereas males exhibited no obvious preference for nitrogen form in nitrogen fertilizations. Abstract We investigated the effects of different inorganic nitrogen forms (NO 3 --N and NH 4 ? -N) on the morphology, physiology, and carbohydrate accumulation of male and female Populus deltoides. Results showed that both NO 3 --N and NH 4 ? -N supply forms significantly increased plant growth, C and N contents of all plant organs, chlorophyll pigment contents, net photosynthesis rates (P n ), and instantaneous photosynthetic N-use efficiencies (PNUE) in the leaves of both male and female P. deltoides. Females exhibited high total plant dry mass accumulation, P n , PNUE, and N contents in leaves but lower non-structure carbohydrate accumulation than males under nitrate treatment. However, males showed significantly higher P n , PNUE, and 15 NH 4 ? in the leaves, free amino acid content, and nitrate reductase (NR) activities than females under each nitrogen form supply treatment.These results suggested that male and female P. deltoides used different adaptive strategies in dry mass accumulation, allocation, and exhibited different interactions between nitrogen and carbon metabolism. Males exhibited higher nitrogen assimilation ability and N-use efficiency than females under nitrogen fertilizations, whereas females showed more sensitivity to inorganic nitrogen forms of treatments and distinct preference for NO 3 --N. Male P. deltoides showed no obvious bias to the two different N forms. Therefore, the different preferences of male and female P. deltoides of N supplied forms can serve as an important strategy for minimizing intraspecific competition between the two genders.

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Section: Sex-specific Difference Of Biomass Accumulation and Allocationmentioning

confidence: 99%

Populus deltoides females are more selective in nitrogen assimilation than males under different nitrogen forms supply

Dong

Guo

et al. 2014

Trees

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“…In maize roots, a correlation was observed between Gln and\or Asn in the root tissue and the suppression of nitrate uptake (Lee et al, 1992). In mycorrhizal beech roots, an external supply of Glu decreased nitrate influx and, as a consequence, net uptake of nitrate (Kreuzwieser et al, 1997).…”

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confidence: 94%

Field and laboratory experiments on net uptake of nitrate and ammonium by the roots of spruce (Picea abies) and beech (Fagus sylvatica) trees

et al. 1998

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During the vegetation periods 1994 and 1995, net uptake of nitrate and ammonium by roots of adult spruce (Picea abies (L.) Karst) and beech (Fagus sylvatica L.) trees was studied at a field site exposed to high loads of N (' Ho$ glwald ', Germany). In addition, uptake experiments were carried out under controlled conditions with young spruce and beech trees grown at normal N supply.In the field, nitrate was not taken up by the roots of spruce trees in appreciable amounts. This was also true for beech except during September 1995. Apparently, beech trees was capable of taking up nitrate, but the environmental condition prevailing at the field site usually prevented net uptake. Net uptake of ammonium in both tree species showed a seasonal course, with maximum rates in mid summer. Rates of ammonium uptake by both species correlated with soil temperature at the field site.Laboratory experiments on the influence of root temperature on uptake of nitrate indicated that uptake rates at temperatures found in the field were low compared with the uptake capacity at optimum temperature. At temperatures of 10 and 15 mC, frequently found in the soil at the field site, net uptake of nitrate by spruce and beech amounted to c. 16 % and 11 %, respectively, of maximum uptake at 25 mC. By contrast, net uptake of ammonium at 10 mC reached 73 % and 31 % of the maximum uptake for spruce and beech trees, respectively. Independent of temperature, rates of nitrate uptake were considerably lower than those of ammonium. In young spruce and beech trees, net uptake of nitrate was significantly inhibited by ammonium at nitrate : ammonium ratios found in the soil solution at the forest site. Preincubation of roots of both species, with amino acids present in the phloem of adult trees at the field site, led to an increase in the amino acid pool in the roots. For spruce trees a correlation between inhibition of uptake of nitrate and enrichment of the roots with the amino compounds Glu, γ-amino butyric acid (Gaba), Gln, and Asn was observed. In beech trees, enrichment of Asp and Gln in the roots correlated with a decrease in net uptake of nitrate. The results of laboratory experiments on the effects of temperature, the nitrate to ammonium ratio in the nutrient solution, and amino acid enrichment in the roots are discussed with special emphasis on the patterns of net uptake of ammonium and nitrate observed in the field.Key words : Nitrate uptake, ammonium uptake, soil temperature, nitrate to ammonium ratio, amino acids. In forest ecosystems, nitrate and ammonium are the most abundant N compounds available to the roots * To whom correspondence should be addressed. E-mail : here!sun2.ruf.uni-freiburg.de of trees. Total amounts of nitrate and ammonium, and the ratio of nitrate to ammonia depend on quality and quantity of N input and on the balance of ammonification, nitrification, immobilization and denitrification processes in the soil (Haynes & Goh,

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“…From these results it appears that Arg, the predominant organic amino compound in root phloem exudates of spruce and, during most of the growing season, also of beech (Geßler et al, 1998 b), is not involved in the regulation of NO $ − uptake by the roots. Since the organic amino compounds fed to the roots can be rapidly metabolized into other amino compounds inside the roots (Lee et al, 1992), the effects observed as a consequence of external supply of amino compounds to the roots cannot immediately be attributed to the compounds fed. Therefore, the composition and content of amino compounds were analysed in roots fed with various amino compounds for comparison with controls.…”

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confidence: 99%

Consequences of high loads of nitrogen for spruce (Picea abies) and beech (Fagus sylvatica) forests

et al. 1998

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High loads of nitrogen to spruce and beech forests can result in a complete inhibition of NO $ − uptake by the roots of the trees. This conclusion is based on (a) a comparison of a field site continuously exposed to high loads of N and a N-limited site, (b) the results of N fertilization of a N-limited field site, and (c) laboratory experiments under controlled environmental conditions. From fertilization experiments in the field it appears that NH % + uptake might become inhibited subsequent to an excessive uptake of NH % + . Apparently, the inhibition of NO $ − uptake by high loads of N to forests is a consequence of an accumulation of organic amino compounds in the roots originating from phloem transport from the shoot to the roots. These amino compounds seem to signal the N demand of the shoot to the roots. At present this function cannot be attributed to an individual organic amino compound in beech or spruce, but Gln is a likely candidate in both species among other compounds, e.g. Glu in spruce or Asp in beech trees. Direct inhibition of NO $ − uptake by NH % + can be excluded from the present studies. The mechanism(s) by which elevated levels of particular organic amino compounds interact with NO $ − uptake remains to be elucidated. This (these) mechanism(s) seem to affect NO $ − influx rather than NO $ − efflux. As a consequence of this (these) mechanism(s), spruce and beech trees can prevent, within a certain physiological window, N over-nutrition when the roots are exposed to excessive amounts of inorganic N. However, inhibition of NO $ − and NH % + uptake by the roots makes more N available for leaching into the ground water and, in addition, for soil microbial processes that result in the production and re-emission of volatile N compounds into the atmosphere.At the ' Ho$ glwald ' site, continuously exposed to high loads of N, 20 % of the N input from throughfall into the spruce and beech plots is re-emitted as NO and N # O. However, the NO to N # O ratio is highly dependent on the tree species, with a preference for NO in the spruce and a preference for N # O in the beech plot. Since at least part of the NO emitted from the soil will be converted inside the canopy in the presence of ozone to NO # that might then be absorbed by the leaves, the portion of the N in the throughfall that will be released from the forest by gaseous N emission is higher in the beech than in the spruce plot. Leaching of NO $ − into the ground water is high in the spruce, but minute in the beech plot. However, this positive effect of beech on ground water quality is achieved at the expense of an enhanced release of radiatively active N gases into the troposphere.Key words : Atmospheric pollution, forest ecosystem, nitrogen allocation, nitrogen fluxes, regulation, nitrogen oxides, ammonia. Both atmospheric and pedospheric sources of nitrogen are available to plants. The contribution of atmospheric N is considered to be low in remote * To whom correspondence should be addressed E-mail : here!sun2.ruf.uni-fre...

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Nitrogen Assimilation and the Control of Ammonium and Nitrate Absorption by Maize Roots

Cited by 165 publications

References 0 publications

Populus deltoides females are more selective in nitrogen assimilation than males under different nitrogen forms supply

Populus deltoides females are more selective in nitrogen assimilation than males under different nitrogen forms supply

Field and laboratory experiments on net uptake of nitrate and ammonium by the roots of spruce (Picea abies) and beech (Fagus sylvatica) trees

Consequences of high loads of nitrogen for spruce (Picea abies) and beech (Fagus sylvatica) forests

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