Efficiency of respiration and energy requirements of N assimilation in roots of <i>Pisum sativum</i>

Devisser, R

doi:10.1111/j.1399-3054.1985.tb02384.x

Cited by 28 publications

(14 citation statements)

References 35 publications

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“…The narla mutation decreases in vitro root NADH NR activity to less than half of normal (28). Apparently, this diminished NADH NR activity (approximately 12 ,mol NO3-g-1 h-1; 28) plus full NAD(P)H NR activity (approximately 14 ,umol NO3-g-1 h-'; 28) was sufficient to sustain normal root assimilation (10-20 ,umol N03-g-' h-1; Fig. 2A).…”

Section: Discussion Root and Plant Nitrate Assimilationmentioning

confidence: 99%

“…These values are consistent with the 1.3 Amol CO2 g-1 min-' estimated for root maintenance respiration (21); consequently, it seems appropriate to use the net CO2 evolution that we measured under nitrogen deprivation as a gauge of maintenance respiration. Maintenance respiration might vary with nitrogen source because of different contributions to altemative pathway respiration (2,12,16), but alternative pathway respiration is negligible in barley roots (4) and, thus, need not be considered here.…”

Section: Respiration Under Nitrogen Deprivationmentioning

confidence: 99%

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Root Respiration Associated with Ammonium and Nitrate Absorption and Assimilation by Barley

Bloom

Sukrapanna²,

Warner³

1992

Plant Physiol.

416

224

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We examined nitrate assimilation and root gas fluxes in a wildtype barley (Hordeum vulgare L. cv Steptoe), a mutant (narla) deficient in NADH nitrate reductase, and a mutant (narla;nar7w) deficient in both NADH and NAD(P)H nitrate reductases. Estimates of in vivo nitrate assimilation from excised roots and whole plants indicated that the narla mutation influences assimilation only in the shoot and that exposure to N03-induced shoot nitrate reduction more slowly than root nitrate reduction in all three genotypes.When plants that had been deprived of nitrogen for several days were exposed to ammonium, root carbon dioxide evolution and oxygen consumption increased markedly, but respiratory quotient-the ratio of carbon dioxide evolved to oxygen consumed did not change. A shift from ammonium to nitrate nutrition stimulated root carbon dioxide evolution slightly and inhibited oxygen consumption in the wild type and narla mutant, but had negligible effects on root gas fluxes in the narla;nar7w mutant. These results indicate that, under NH4' nutrition, 14% of root carbon catabolism is coupled to NH4' absorption and assimilation and that, under N03-nutrition, 5% of root carbon catabolism is coupled to N03-absorption, 15% to N03-assimilation, and 3% to NH4+ assimilation. The additional energy requirements of N03-assimilation appear to diminish root mitochondrial electron transport. Thus, the energy requirements of NH4' and N03-absorption and assimilation constitute a significant portion of root respiration.Nitrogen assimilation is among the most energy-intensive processes in plants, requiring the transfer of two electrons per N03 converted to NO2, six electrons per N02 converted to NH4', and two electrons and one ATP per NH4' converted to glutamate. To provide sufficient electrons for these reactions, plants may divert reductant from mitochondrial electron transport. During dark N03-assimilation, shoots of a higher plant (8) and algae (18, 29) evolved CO2 significantly faster than they consumed O2, presumably because the TCA cycle or the oxidative pentose phosphate pathway catabolized substrates and transferred some electrons to N03-and N02-rather than to O2. These results indicate that, in the dark, shoots expend up to 25% of their respiratory energy on nitrogen assimilation (8).Plants from 5 to 95% of the N03-absorbed from the rhizosphere (1, 20). Estimates of root nitrogen acquisition and the associated energy transfers have been limited (2, 4, 5, 10, 12, 14-16, 23, 26, 27), and these could not distinguish among expenditures for tissue maintenance, root growth, NH4' and NO3-absorption, and NH4' and N03-assimilation. Root respiration is usually determined from net 02 uptake, yet N03-, N02-, and NH4' can substitute for 02 as electron acceptors during nitrogen assimilation. Root carbon catabolism might be a more pertinent measure, but analysis of dissolved CO2 has required discontinuous sampling (24,29) or elevated CO2 concentrations (17). The present study employed an instrumentation system that simultaneously mo...

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Section: Discussion Root and Plant Nitrate Assimilationmentioning

confidence: 99%

Section: Respiration Under Nitrogen Deprivationmentioning

confidence: 99%

Root Respiration Associated with Ammonium and Nitrate Absorption and Assimilation by Barley

Bloom

Sukrapanna²,

Warner³

1992

Plant Physiol.

416

224

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“…Thus, the increased capacities of alternative respiratory pathways in ammonium-grown seedlings may also result in more respiratory oxidation of matrix NADH and less export of redox equivalents to the cytosol. Results showing that more reductant must be oxidized by the respiratory chain under ammonium nutrition have also been reported for barley, wheat, maize, and pea roots (28)(29)(30).…”

Section: Discussionmentioning

confidence: 75%

Arabidopsis SIZ1 positively regulates alternative respiratory bypass pathways

et al. 2012

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Plant mitochondria possess alternative respiratory pathways mediated by the type II NAD(P)H dehydrogenases and alternative oxidases. Here, E3 SUMO ligase was shown to regulate alternative respiratory pathways and to participate in the maintenance of carbon and nitrogen balance in Arabidopsis. The transcript abundance of the type II NAD(P)H dehydrogenases NDA2 and NDB2 and alternative oxidases AOX1a and AOX1d genes was low in siz1-2 mutants compared to that in wild-type. The addition of nitrate or ammonium resulted in a decrease or an increase in the expression of the same gene families, respectively, in both wild-type and siz1-2 mutants. The amount of free sugar (glucose, fructose and sucrose) was lower in siz1-2 mutants than that in wild-type. These results indicate that low nitrate reductase activity due to the AtSIZ1 mutation is correlated with an overall decrease in alternative respiration and with a low carbohydrate content to maintain the carbon to nitrogen ratio in siz1-2 mutants. [BMB Reports 2012; 45(6): 342-347]

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“…On the other hand, this pathway accounts for 20 to 35% of the respiration by non-nodulated roots of legumes utilizing nitrate or ammonium (5,7,17). This difference has been shown to be related to the chemical form of nitrogen, not to the amount supplied (5).…”

Section: Introductionmentioning

confidence: 99%

“…The activity of the alternative, nonphosphorylating electron transport pathway (CN-resistant respiration) is low or absent in the roots of leguminous plants fixing N2 (5,7,16,17). On the other hand, this pathway accounts for 20 to 35% of the respiration by non-nodulated roots of legumes utilizing nitrate or ammonium (5,7,17).…”

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confidence: 99%

Alternative Path Mediated ATP Synthesis in Roots of Pisum sativum upon Nitrogen Supply

Visser

Brouwer²,

Posthumus³

1986

Plant Physiol.

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Changes in the efficiency of root respiration were examined on intact plants of Pisum satiyum L. cv Rondo after addition of nitrate or ammonium to the culture solutions. Nitrate was absorbed immediately after addition and elicited a respiratory rise (02-uptake as well as CO2-production) to 160% at most. This occurred both in roots of plants fixing N2 and in those of non-nodulated plants pregrown for 1 or 2 weeks on a nitrogen-free culture solution. In older plants, used after 2 weeks of Nfree growth, the full capacity of the cytochrome path was engaged in root respiration. This was demonstrated by the absence of an effect of the uncoupler carbonylcyanide m-chlorophenylhydrazone in the presence of 25 millimolar salicylhydroxamate, an inhibitor of the alternative path. In these plants more than 90% of the nitrate-induced stimulation of root respiration was salicylhydroxamate-sensitive. In young plants, used after I week of N-free growth, the cytochrome path was not saturated. Its activity increased instantaneously at the expense of alternative path activity, which initially dropped to zero and subsequently increased to 160% of the control 7 hours after nitrate supply. The rate of photosynthesis rose to 120% of the control, but not before 1 hour after nitrate supply, suggesting that the stimulation of root respiration was not due to a higher rate of photosynthesis. Experiments with plants grown with a split-root system showed that respiration rate and alternative path activity only increased in the root halves exposed to nitrogen. Ammonium was equally effective as nitrate in stimulating root respiration. These results lead to the conclusion that alternative-path mediated root respiration contributes to synthesis of ATP during at least the first 24 hours following nitrogen supply.The activity of the alternative, nonphosphorylating electron transport pathway (CN-resistant respiration) is low or absent in the roots of leguminous plants fixing N2 (5, 7, 16, 17). On the other hand, this pathway accounts for 20 to 35% of the respiration by non-nodulated roots of legumes utilizing nitrate or ammonium (5,7,17). This difference has been shown to be related to the chemical form of nitrogen, not to the amount supplied (5). Thus, a high activity of the alternative path may be specifically induced by nitrogen-containing ions.The effects of uptake and assimilation of nitrogen on root respiration have been the subject of research for more than half a century (10, 1 1, 20 MATERIALS AND METHODS Plant Material. Plants ofPisum sativum L. cv Rondo (Cebeco, Dronten, The Netherlands) were raised from seed and grown in culture solution in growth cabinets as described elsewhere (7). Seeds of plants to be grown symbiotically were inoculated with Rhizobium leguminosarum strain PF2. Germination occurred in vermiculite moistened with demineralized water during 6 d, except for plants grown with a split-root system (see below). The composition of the culture solution was as described by Smakman and Hofstra (23)

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Efficiency of respiration and energy requirements of N assimilation in roots of Pisum sativum

Cited by 28 publications

References 35 publications

Root Respiration Associated with Ammonium and Nitrate Absorption and Assimilation by Barley

Root Respiration Associated with Ammonium and Nitrate Absorption and Assimilation by Barley

Arabidopsis SIZ1 positively regulates alternative respiratory bypass pathways

Alternative Path Mediated ATP Synthesis in Roots of Pisum sativum upon Nitrogen Supply

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