The influence of ammonium on nitrate reduction in wheat seedlings

Minotti, P. L.; Williams, Doris Craig; Jackson, W. A.

doi:10.1007/bf00386459

Cited by 60 publications

(23 citation statements)

References 7 publications

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“…The light intensity was 194 hectolux at plant height, and temperature was 24 +2 C and 17 + 2 C during the light and dark periods, respectively. These growth conditions produced seedlings low in nitrogen and high in carbohydrate content (16). Thus the seedlings would be expected to absorb and assimilate nitrate nitrogen at a rapid rate, provided the required transport, reduction, and assimilatory systems were present.…”

Section: Methodsmentioning

confidence: 99%

Nitrate Uptake and Assimilation by Wheat Seedlings during Initial Exposure to Nitrate

Ashley

Jackson²,

Volk³

1975

Plant Physiol.

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Nitrate uptake, reduction, and translocation were examined in intact, 14-day-old, nitrogen-depleted wheat (Triticum vulgare var. Knox) seedlings during a 9-hour exposure to 0.2 mM Ca(NO3)2. The nitrate uptake rate was low during the initial 3-hour period, increased during the 3-to 6-hour period, and then declined. By the 3rd hour, 14% of the absorbed nitrate had been reduced, and this increased to 36% by the 9th hour. Shoots accumulated reduced '5N more rapidly than roots and the ratio of reduced "N to '5N-nitrate was higher in the shoots. A significant proportion of the total reduction occurred in the root system under these experimental conditions. Accumulation of "N in ethanol-insoluble forms was evident in both roots and shoots by the 3rd hour and, after 4.5 hours, increased more rapidly in shoots than in roots.An experiment in which a 3-hour exposure to 0.2 mM Ca('NO3)2 was followed by a 12-hour exposure to 0.2 mM Ca ("NO3)2 revealed a half-time of depletion of root nitrate of about 2.5 hours. A large proportion of this depletion, however, was due to loss of '5N-nitrate to the ambient "N-nitrate solution. The remaining pool of '5N-nitrate was only slowly available for reduction. Total "N translocation to the shoot was relatively efficient during the first 3 hours after transfer to Ca ("NO3)2 but it essentially ceased after that time in spite of significant pools of "N-nitrate and a-amino-"N remaining in the root tissue.Many higher plant species (3, 9, 10, 14, 15), as well as tobacco cell cultures (6) and Penicilliumii chrysogenum (5) experiments were conducted. The first involved exposure of nitrogen-depleted plants to nitrate solutions highly enriched in "N; the results show the effectiveness with which absorbed nitrate (a) accumulated in roots and shoots, (b) was reduced, and (c) was incorporated into protein during a 9-hr period. In the second experiment, a 3-hr exposure to highly enriched "Nnitrate was followed by an additional 12 hr in "N-nitrate, permitting an assessment of the fate of the initially absorbed "N-nitrate during the early phases of recovery from the nitrogen-depleted state. MATERIALS AND METHODSWheat seed (Triticum vulgare var. Knox) were kept moist with 10-' M CaSO4, germinated 3 days in darkness, and transferred to small plastic cups containing holes in the bottom through which the roots were threaded. Each cup contained six seedlings and henceforth will be referred to as a culture. Roots of the required numbers of cultures were placed in 13-liter plastic tanks containing nutrients at one-fifth the concentrations given by Hoagland and Arnon (7) for minus nitrogen solutions. The plants were grown in these solutions for 11 days in a controlled environment chamber. Sixteen hr of light and 8 hr of darkness were used. The light intensity was 194 hectolux at plant height, and temperature was 24 +2 C and 17 + 2 C during the light and dark periods, respectively. These growth conditions produced seedlings low in nitrogen and high in carbohydrate content (16). Thus the seedlings would be...

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Section: Methodsmentioning

confidence: 99%

Nitrate Uptake and Assimilation by Wheat Seedlings during Initial Exposure to Nitrate

Ashley

Jackson²,

Volk³

1975

Plant Physiol.

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“…In contrast, the work of MINOTTI et a/. (8) suggested that NH, + can influence the N0 3 -uptake process directly rather than indirectly via its effect on N0 3 -reductive activity.…”

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confidence: 91%

Effects of various environmental and medium conditions on the response of Indica and Japonica rice plants to ammonium and nitrate nitrogen

Ohira

1981

Soil Science and Plant Nutrition

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“…When present in the external medium, NH4' is a potent inhibitor of NO3-uptake by barley plants (15, 25), and of N03 accumulation in several other species, including wheat (19,20) ryegrass (2, 16), apple (10), and corn (23). It should be stressed, however, that a reduction of NO3-accumulation by NH4' might be caused by effects upon NO3-translocation or reduction rather than via direct effects on NO3-uptake per se.…”

Section: Introductionmentioning

confidence: 99%

“…Both short term (direct) effects of NH4' on the activities of the nitrate transporter, as well as long term (indirect) effects, possibly via transcription-dependent events, might be envisioned. In addition, exposure oftissues to products of NO3-assimilation, the amino acids, would be anticipated to influence rates of NO3-uptake.When present in the external medium, NH4' is a potent inhibitor of NO3-uptake by barley plants (15, 25), and of N03 accumulation in several other species, including wheat (19,20) ryegrass (2, 16), apple (10), and corn (23). It should be stressed, however, that a reduction of NO3-accumulation by NH4' might be caused by effects upon NO3-translocation or reduction rather than via direct effects on NO3-uptake per se.…”

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confidence: 99%

Short Term Studies of Nitrate Uptake into Barley Plants Using Ion-Specific Electrodes and ³⁶ClO₃⁻

Deane‐Drummond¹,

Glass²

1983

Plant Physiol.

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The influence of NH4', in the external medium, on fluxes of NO3-and K were investigated using barley (Hordeum vulgare cv Betzes) plants.NWV was without effect on NO3-(3'10C3-) influx whereas inhibition of net uptake appeared to be a function of previous N03-provision. Plants grown at 10 micromolar NO3-were sensitive to external NHW when uptake was measured in 100 micromolar NO3-. By contrast, NO3-uptake (from 100 micromolar NO3-) by plants previously grown at this concentration was not reduced by NI-14 treatment. Plants pretreated for 2 days with 5 millimolar NO3-showed net efflux of NO3-when roots were transferred to 100 micromolar NO3-. This efflux was stimulated in the presence of NH4'. NH4' also stimulated NO3-efflux from plants pretreated with relatively low nitrate concentrations. It is proposed that short term effects on net uptake of NO3-occur via effects upon efflux.By contrast to the situation for NO3-, net K' uptake and influx of 'Rb+-labeled K' was inhibited by NH4' regardless of the nutrient history of the plants. Inhibition of net K' uptake reached its maximum value within 2 minutes of NH4' addition. It is concluded that the latter ion exerts a direct effect upon K' influx.In barley, Lewis et al. (15), for example, showed that NH4' inhibited NO3-accumulation in the root and shoot and NO3-translocation to shoots although NO3-uptake was not measured directly. Recently, MacKown et al. (17,18) have shown that NH14' inhibits NO3-uptake and NO3-reduction in corn plants.Their results suggest that almost all the effect of NH4' on uptake of N03-is via its effect on the reduction step. There have also been reports of stimulated NO3-uptake arising as a consequence of NH4' pretreatment as in the case of seedlings of wheat (21) and corn (18).The almost universal choice of relatively long experimental periods (usually 2 to 24 h) for the investigation ofeffects of NH4+ upon nitrate uptake has made it extremely difficult to distinguish between effects on nitrate uptake per se and subsequent effects upon the properties (selectivity, turnover, etc.) of the nitrate transporter or effects on nitrate reduction and translocation (e.g. 17, 18). Both inhibition (9, 23, 24, 26) and stimulation (21) of in vitro nitrate reductase activity, following NH4' pretreatment, have been documented. Other workers using corn have shown that NH4+ inhibits NO3-reduction in vivo (18). However, the possible direct or indirect effects of NH4+ on the turnover of the nitrate transport proteins (presuming they are in fact proteins) will remain an open question until such proteins can be biochemically characterized.The potential importance of NH4, in the regulation of N03-metabolism has been widely recognized and explored in numerous studies of nitrate assimilation in micro-organisms and higher plants (e.g. 2-4, 12, 14). Considering the intermediary role of NH4+ in nitrate utilization, the former ion must represent a likely candidate for feedback effects on uptake and/or reduction of nitrate. Both short term (direct) effects of NH4' on...

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The influence of ammonium on nitrate reduction in wheat seedlings

Cited by 60 publications

References 7 publications

Nitrate Uptake and Assimilation by Wheat Seedlings during Initial Exposure to Nitrate

Nitrate Uptake and Assimilation by Wheat Seedlings during Initial Exposure to Nitrate

Effects of various environmental and medium conditions on the response of Indica and Japonica rice plants to ammonium and nitrate nitrogen

Short Term Studies of Nitrate Uptake into Barley Plants Using Ion-Specific Electrodes and ³⁶ClO₃⁻

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The influence of ammonium on nitrate reduction in wheat seedlings

Cited by 60 publications

References 7 publications

Nitrate Uptake and Assimilation by Wheat Seedlings during Initial Exposure to Nitrate

Nitrate Uptake and Assimilation by Wheat Seedlings during Initial Exposure to Nitrate

Effects of various environmental and medium conditions on the response of Indica and Japonica rice plants to ammonium and nitrate nitrogen

Short Term Studies of Nitrate Uptake into Barley Plants Using Ion-Specific Electrodes and 36ClO3−

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Short Term Studies of Nitrate Uptake into Barley Plants Using Ion-Specific Electrodes and ³⁶ClO₃⁻