Ammonium Uptake by Rice Roots (II. Kinetics of 13NH4+ Influx across the Plasmalemma)

Wang, M. Y.; Siddiqi, M. Yaeesh; Ruth, Thomas J.; Glass, Anthony D. M.

doi:10.1104/pp.103.4.1259

Cited by 250 publications

(246 citation statements)

References 21 publications

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“…Similar uptake kinetics have been observed for NO,-influx in barley (Siddiqi et al, 1990) and in the diatom Skeletonema costatum (Serra et al, 1978). Likewise, NH,+ influx in rice is mediated by saturable and linear transport systems (Wang et al, 1993). A dual pattern of K+ influx was also reported in Chlorella (Kannan, 1971), but influx at high [K+I, appeared to occur via a second saturable system.…”

Section: Discussionsupporting

confidence: 53%

“…In the present study, the influx isotherm for K'(4ZK+ and "Rb+) influx was resolved into a biphasic pattern, with saturable and nonsaturable components. This corresponds to earlier observations describing the patterns of K+ uptake by barley roots (Epstein and Hagen, 1952) and corn roots (Kochian and Lucas, 1982) and more recent studies of NO,-uptake in barley roots (Siddiqi et al, 1990) and NH4+ uptake by rice roots (Wang et al, 1993). The saturable HATS corresponds to Epstein's mechanism 1 (Epstein and Hagen, 1952 (Malhotra and Class, 1995).…”

Section: Discussionmentioning

confidence: 95%

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Potassium Fluxes in Chlamydomonas reinhardtii (I.Kinetics and Electrical Potentials)

Malhotra

Glass

1995

Plant Physiol.

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Section: Discussionsupporting

confidence: 53%

Section: Discussionmentioning

confidence: 95%

Potassium Fluxes in Chlamydomonas reinhardtii (I.Kinetics and Electrical Potentials)

Malhotra

Glass

1995

Plant Physiol.

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“…Although the regulation of NH % + uptake in the root has received less attention than the regulation of NO $ − uptake, it has been shown that the uptake of NH % + can also be regulated via effects on influx. Studies of "$NH % + showed a strong negative down-regulation of influx in response to an increased supply of NH % + to the root (Wang et al, 1993). The signals involved might be unmetabolized NH % + in the root cells or, as in the regulation of NO $ − influx, a reduced N compound translocated from the shoot.…”

Section: Contribution Of Atmospheric N and S Deposition To The N And mentioning

confidence: 99%

Impact of gaseous nitrogen deposition on plant functioning

et al. 1998

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 Dry deposition of NH$ and NO x (NO and NO # ) can affect plant metabolism at the cellular and whole-plant level. Gaseous pollutants enter the plant mainly through the stomata, and once in the apoplast NH $ dissolves to form NH % + , whereas NO # dissolves to form NO $ − and NO # − . The latter compound can also be formed after exposure to NO. There is evidence that NH $ -N and NO x -N can be reversibly stored in the apoplast. Temporary storage might affect processes such as absorption rate, assimilation and re-emission. Once formed, NO $ − and NO # − can be reduced, and NH % + can be assimilated via the normal enzymatic pathways, nitrate reductase (NR), nitrite reductase and the glutamine synthetase\glutamate synthase (GS\GOGAT) cycle. Fumigation with low concentrations of atmospheric NH $ increases in vitro glutamine synthetase activity, but whether this involves both or only one of the GS isoforms is still an open question. There seems to be no correlation between fumigation with low concentrations of NH $ and in vitro GDH activity. The contribution of atmospheric NH $ and NO # deposition to the N budget of the whole plant has been calculated for various atmospheric pollutant concentrations and relative growth rates (s). It is concluded that at current ambient atmospheric N concentrations the direct impact of gaseous N uptake by foliage on plant growth is generally small. Key words : Apoplastic storage, gaseous nitrogen deposition, glutamate dehydrogenase, glutamine synthetase, plant nitrogen demand, sulphur dioxide root\shoot interaction, ammonia, nitrogen oxides. Anthropogenic emissions of nitrogen-containing air pollutants far exceed natural emissions in Europe and North America. These emissions cause two types of effect : generation of tropospheric O $ , and excess N deposition, which can result in direct phytotoxic effects, eutrophication, acidification and stimulation of greenhouse gas production. Anthropogenic emissions of N-containing air pollutants have resulted in atmospheric N deposition 5-20 times higher than in natural conditions. Indications of N excess in the field can be seen from : (1) changes in the species composition of indigenous vegetation types, with an increase in nitrophilous species and a decrease in others, and (2) increases in foliar N * To whom correspondence should be addressed. E-mail : g.stulen!biol.rug.nl. Abbreviations : GDH, glutamate dehydrogenase ; GS, glutamine synthetase ; GOGAT, glutamate synthase ; , net nitrate uptake rate ; NR, nitrate reductase ; P95, 95 percentile ; , plant nitrogen content ; , relative growth rate.

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“…For evaluating the underlying kinetic constants (i.e. apparent V max and apparent K m ) five different equations describing two to three uptake systems were provisionally fitted to the data (see also Borstlap 1983;Wang et al 1993):…”

Section: Statistical Treatment and Calculationsmentioning

confidence: 99%

The effects of light on induction, time courses, and kinetic patterns of net nitrate uptake in barley

Peuke

Jeschke

1998

Plant Cell & Environment

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Barley seedlings (Hordeum vulgare L.) were grown hydroponically with (induced) or without (uninduced) nitrate in a light/dark cycle with high photon flux density to determine the effects of light on time courses, induction and kinetics of net nitrate uptake. Nitrate uptake was induced by external nitrate in both light and dark and was prevented by 1 mol m -3 p-fluorophenylalanine. In high light, nitrate uptake was about 2-fold higher than in low light. During time course experiments the uptake rates oscillated due to daily light-dark changes. Rates of nitrate uptake also increased at about 2200 h during continuous darkness. This increase coincided approximately with the time at which the dark period started during the previous culture of the plants, indicating that it was due to a mechanism associated with an endogenous diurnal rhythm. When calculating the kinetics of nitrate uptake, a model with two saturable systems, including a high-affinity system (HATS) and a low-affinity system (LATS), gave the best fit to data in all treatments. The apparent affinity of the HATS ranged from 7·7 to 12·2 mmol m -3 in induced plants in all light conditions. The effect of light on the HATS was mainly an increase of apparent V max in the step from low to high light. In uninduced plants the HATS operated at a very low activity which was strongly enhanced during induction. Interpretation of the calculated kinetics of the LATS was much more difficult on the basis of net uptake data. The apparent affinity of the LATS increased from 24·3 mol m -3 in low light up to 0·17 mol m -3 after acceleration in high light. These extreme changes in apparent affinity of the LATS could not be explained satisfactorily, and the nature of this system is also discussed with respect to the method used.

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Ammonium Uptake by Rice Roots (II. Kinetics of 13NH4+ Influx across the Plasmalemma)

Abstract: Short-term influxes of 13NH4+ were measured in intact roots

Cited by 250 publications

References 21 publications

Potassium Fluxes in Chlamydomonas reinhardtii (I.Kinetics and Electrical Potentials)

Potassium Fluxes in Chlamydomonas reinhardtii (I.Kinetics and Electrical Potentials)

Impact of gaseous nitrogen deposition on plant functioning

The effects of light on induction, time courses, and kinetic patterns of net nitrate uptake in barley

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