Ammonium inactivation of nitrate reductase in Lemna minor L.

Orebamjo, T. O.; Stewart, George R.

doi:10.1007/bf00385402

Cited by 30 publications

(10 citation statements)

References 13 publications

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“…Nitrogen source may influence NRA. It has been suggested that NH 4 + may decrease NRA because of feedback inhibition from end products of NH 4 + assimilation (Orebamjo and Stewart 1975). By contrast, other studies contend that NH 4 + inhibition rarely occurs and NH 4 + is often required for optimal NRA (Mohanty and Fletcher 1976;Beevers and Hageman 1980).…”

Section: Introductionmentioning

confidence: 95%

Nitrate reductase activity and nitrogen compounds in xylem exudate of Juglans nigra seedlings: relation to nitrogen source and supply

Nicodemus

Salifu

Jacobs

2008

Trees

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Nitrogen (N) limits plant productivity and its uptake and assimilation may be regulated by N source, N availability, and nitrate reductase activity (NRA). Knowledge of how these factors interact to affect N uptake and assimilation processes in woody angiosperms is limited. We fertilized 1-year-old, half-sib black walnut (Juglans nigra L.) seedlings with ammonium (NH 4 + ) [as (NH 4 ) 2 SO 4 ], nitrate (NO 3 -) (as NaNO 3 ), or a mixed N source (NH 4 NO 3 ) at 0, 800, or 1,600 mg N plant -1 season -1. Two months following final fertilization, growth, in vivo NRA, plant N status, and xylem exudate N composition were assessed. Specific leaf NRA was higher in NO 3 --fed and NH 4 NO 3 -fed plants compared to observed responses in NH 4 + -fed seedlings. Regardless of N source, N addition increased the proportion of amino acids (AA) in xylem exudate, inferring greater NRA in roots, which suggests higher energy cost to plants. Root total NRA was 37% higher in NO 3 --fed than in NH 4 + -fed plants. Exogenous NO 3 -was assimilated in roots or stored, so no difference was observed in NO 3 -levels transported in xylem. Black walnut seedling growth and physiology were generally favored by the mixed N source over NO 3 -or NH 4 + alone, suggesting NH 4 NO 3 is required to maximize productivity in black walnut. Our findings indicate that black walnut seedling responses to N source and level contrast markedly with results noted for woody gymnosperms or herbaceous angiosperms.

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Section: Introductionmentioning

confidence: 95%

Nitrate reductase activity and nitrogen compounds in xylem exudate of Juglans nigra seedlings: relation to nitrogen source and supply

Nicodemus

Salifu

Jacobs

2008

Trees

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“…The higher rate of N-assimilation in the presence of NH4+ might result in an increase of this compound, compared to the situation with NO3-alone as N source (13,14). However, contradictory results have been obtained with NR from Lemna minor, which was appreciably inactivated by NH4+ within 1 h (21). Conclusions.…”

Section: Discussionmentioning

confidence: 97%

“…The NRA in green tissues of higher plants seems to be generally unaffected or stabilized by NHI4+ (3, 19, 24) whereas a pH-dependent inhibition has been noted in roots (20,24). This pattern is, however, not universal (for Lemna, see [21]) and seems to be very much dependent on plant material, the way of culturing the plants, and the treatment ofthe plants during assay.In two accompanying papers we have presented data on the characteristics of NO3-uptake and NO3-reduction in Lemna gibba L. (12, 14). The aim of the present study was to clarify the nature of the NH4' effect on membrane NO3-transport (using '3NO3-), and to investigate the effect of NH4' on accumulation and reduction of NO3-.…”

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confidence: 99%

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Nitrogen Utilization in Lemna

Ingemarsson¹,

Oscarson²,

Ugglas³

et al. 1987

Plant Physiol.

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The effects ofammonium application on nitrate utilization were studied in N-limited cultures of Lemna gibba L. G3. Addition of ammonium instantaneously inhibited net nitrate uptake by at least 60%, followed by a slight recovery. The inhibition was equally clear after near-complete inactivation of glutamine synthetase by application of L-methionine-D,Lsulfoximine. Experiments where "MN-abeled nitrate was used as an influx tracer revealed that ammonium specifically inhibited influx, but did not promote nitrate efflux. Nitrate accumulation was relatively more inhibited than nitrate reduction and net uptake. Nitrate reductase, extracted and assayed in vitro in the presence of the thiol proteinase inhibitor leupeptin, was unaffected by short-term treatment of the plants with either nitrate, ammonium, or ammonium nitrate. Nitrate reductase activity recovered in the absence of leupeptin was considerably lower, however, it was enhanced by all the nitrogen sources, with ammonium as the most potent. It is argued that the effect of ammonium on nitrate utilization in Lemna is due to inhibition of nitrate influx, and that the effect should be attributed to ammonium itself, not to a newly formed nitrogen derivative. The decreased nitrate flux caused a decrease in nitrate reduction, whereas the activity of nitrate reductase per se rather is stabilized by presence of ammonium.Short-term inhibition of net NO3-uptake by supply of NH4' is well documented for cyanobacteria and algae (26). In higher plants, however, the effect of NH4' is more variable, ranging from a transient stimulation (1) to a total inhibition of net N03 uptake (6,8). Ammonium could affect net NO3-uptake by interfering either with membrane NO3-transport or with utilization of NO3-within the plant tissue. By using 36C103-as an analog for NO3-, it was shown that NH4+ stimulated NO3-efflux in several species (4-7), although no such effect was found in barley using '3N03-(17). Studies with '5NO3-(18) and '3N03-(11, 22) rather pointed to an inhibition of the influx component of net NO3-uptake. There is only limited knowledge on the cause for inhibition of NO3-uptake; it has been attributed to NH4+-induced membrane depolarization (27), or to a regulatory compound formed in primary NH4' assimilation (1, 10).Ammonium has also been reported to affect NR2; thus, some of the observed effects of NH4+ might be due to altered NRA. In algae, however, the effect of NH41 on NRA is normally too slow to account for the usually prompt inhibition of NO3-uptake ' Supported by the Swedish Natural Science Research Council. 2 Abbreviations: NR, nitrate reductase; FW, fresh weight; GS, glutamine synthetase; MSO, L-methionine-D,L-sulfoximine; NRA, nitrate reductase activity.(16). The NRA in green tissues of higher plants seems to be generally unaffected or stabilized by NHI4+ (3, 19, 24) whereas a pH-dependent inhibition has been noted in roots (20,24). This pattern is, however, not universal (for Lemna, see [21]) and seems to be very much dependent on plant material, the way of ...

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“…-Kaiser and Huber 2001) are affected by the relative uptake and metabolization of NO 3 − and NH 4 + (Britto and Kronzucker 2002). Indeed, NH 4 + can affect NO 3 − metabolism, because NH 4 + , or its metabolic products, can inactivate (Orebamjo and Stewart 1975a) and/ or repress NRA (Orebamjo and Stewart 1975b). The objective of this study was therefore to test whether NH 4 + can indeed inhibit the stimulation of NRA by NO 3 − in summer semi-deciduous species.…”

Section: Introductionmentioning

confidence: 98%

Plant tolerance of ammonium varies between co-existing Mediterranean species

et al. 2015

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Background Previous studies showed that the two main Mediterranean plant functional groups, summer semideciduous and evergreen sclerophylls, differ in soil characteristics and nitrate (NO 3 − ) use strategies: even though summer semi-deciduous plants have higher NO 3 − availability than evergreen sclerophylls, NO 3 − reduction (i.e., nitrate reductase activity-NRA) is lower, and is not stimulated by substrate (NO 3 − ) availability. Aims Test if in Cistus albidus plants, a summer semideciduous species, ammonium (NH 4 + ) can inhibit NRA, despite the availability of NO 3 − , and whether Olea europaea plants, evergreen sclerophyll, are more tolerant of NH 4 + than the former. Methods One-year-old C. albidus and wild O. europaea potted plants were supplied with both NH 4 + and NO 3 − at increasing levels (0.1; 0.2; 0.4; 0.8 and 1.6 % N). Tolerance of NH 4 + was evaluated using integrative (mortality and biomass accumulation) and plant nitrogen metabolism parameters (in vitro NRA and concentrations of NO 3 − and NH 4 + ) determined in roots and leaves. Results C. albidus plants were consistently less NH 4 + tolerant than O. europaea, displaying: higher mortality; growth and NRA inhibition and NH 4 + accumulation above 0.2 % NH 4 NO 3 -N in the soil. In contrast, O. europaea plants seemed to buffer the full range of tested NH 4 NO 3 levels. Conclusions C. albidus plants were less NH 4 + tolerant than O. europaea. The ecological implications of this contrasting NH 4 + tolerance are discussed.

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Ammonium inactivation of nitrate reductase in Lemna minor L.

Cited by 30 publications

References 13 publications

Nitrate reductase activity and nitrogen compounds in xylem exudate of Juglans nigra seedlings: relation to nitrogen source and supply

Nitrate reductase activity and nitrogen compounds in xylem exudate of Juglans nigra seedlings: relation to nitrogen source and supply

Nitrogen Utilization in Lemna

Plant tolerance of ammonium varies between co-existing Mediterranean species

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