The nitrogen-sink is involved in the regulation of nitrogenase activity in white clover after defoliation

Hartwig, Ueli A.; Heim, Ignaz; Lúscher, A.; Nösberger, J.

doi:10.1034/j.1399-3054.1994.920302.x

Cited by 7 publications

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“…Indeed in both studies, the nodule mass of W and B was lower than that of R, although the ARA of R tended to be lower, indicating a lower N accumulation and N 2 dependent growth [16]. This observation agrees with the hypothesis of regulation of nodule nitrogenase activity by plant N demand [13]. However, this conclusion would require further exploration, including the C genotype, not tested previously, which had a high nodule mass and activity (Tab.…”

Section: Discussionsupporting

confidence: 81%

Genotypic difference in the short-term response of nitrogenase activity (C₂H₂ reduction) to salinity and oxygen in the common bean

et al. 2001

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difference in the short-term response of nitrogenase activity (C_2H_2 reduction) to salinity and oxygen in the common bean. Agronomie, EDP Sciences, 2001, 21 (6- Abstract -Four genotypes of common bean (Phaseolus vulgaris L.) differing in seed color, were grown hydroponically in a growth chamber to study the short-term effects of 0.1 M NaCl on their symbiotic acetylene reducing activity (ARA). For all genotypes, the ARA was reduced dramatically during the first hour following NaCl application. This was followed by a slower decrease during the next 5 h during which genotypical differences in response to salinity were found. When expressed as percent of the control, the redseed genotype was significantly less inhibited by NaCl than the three others. For all genotypes, the increase in ARA after raising rhizosphere pO 2 was affected by the NaCl treatment. With NaCl the red-seed genotype showed the highest stimulation by pO 2 , which was associated with its higher tolerance to NaCl application. However for all genotypes, raising pO 2 did not allow a complete recovery from the NaCl effect. It is concluded that nitrogenase inhibition by NaCl application in common bean varies among genotypes, and is associated with a short-term nodule limitation by O 2 diffusion, although other mechanisms may also be involved in nodule inhibition by NaCl. N 2 fixation / oxygen diffusion / Phaseolus vulgaris / Rhizobium / salinity Résumé -Effets à court terme de la salinité sur l'activité nitrogénase nodulaire et sa réponse à l'oxygène chez le haricot. Quatre génotypes de haricot (Phaseolus vulgaris L.) différant par la couleur des téguments de leur graine, ont été cultivés hydroponiquement en chambre de culture afin d'étudier les effets de NaCl sur leur fixation symbiotique d'azote et leur croissance. L'activité réductrice de l'acétylène (ARA) était fortement réduite pendant la première heure suivant l'application de NaCl. Cette baisse initiale était suivie d'une baisse plus lente durant laquelle des différences variétales ont été mesurées. Le génotype R était significativement moins inhibé par NaCl que les 3 autres. Pour tous les génotypes, la stimulation d'ARA par augmentation de la pO 2 rhizosphérique était modifiée par le traitement salin. Avec NaCl, le génotype R présenta la plus forte stimulation par la pO 2 , qui était associée à sa plus forte tolérance à NaCl. Toutefois quel que soit le génotype, l'élévation de pO 2 ne compensa pas totalement l'inhibition par NaCl. Il est conclu que l'inhibition de la nitrogénase par la salinité chez le haricot fixateur d'azote varie entre génotypes, et est associée à une limitation du métabolisme nodulaire par un manque d'O 2 , bien que d'autres mécanismes d'inhibition par NaCl puissent être impliqués.

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Section: Discussionsupporting

confidence: 81%

Genotypic difference in the short-term response of nitrogenase activity (C₂H₂ reduction) to salinity and oxygen in the common bean

et al. 2001

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“…An early report by Pate, Gunning, and Briarty [12] suggested that lower rates of water movement out of the nodule during drought stress may restrict the export of products of N 2 fixation, thus inhibiting nitrogenase activity via a feedback mechanism. Several authors have also proposed that N 2 fixation in legumes might be regulated under other stress factors by a feedback mechanism involving N metabolism and the pool of soluble N in the plant [4,10,11,24]. Here we review new evidence on the interaction between nodule function under drought and ureide metabolism at the whole plant level.…”

Section: Introductionmentioning

confidence: 99%

Feedback regulation of symbiotic N₂ fixation under drought stress

2001

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-Although drought inhibition of N 2 fixation is general among rhizobium-legume symbioses, a large genetic variation has been found among legume species and cultivars in the N 2 fixation sensitivity to water deficits. Legume species that transport ureides from the nodules were found to be much more drought-sensitive than those that transport amides. It was concluded that a feedback mechanism involving ureide level may control N 2 fixation under drought. Consistent with this observation, the drought tolerance of N 2 fixation in soybean was associated with low concentrations of ureides in plant tissues. Experimental evidence for a direct inhibition of nitrogenase activity by ureides application supported the feedback hypothesis, although the exact nature of the chemical compound involved in the signal is still unknown. The basis for ureide accumulation is hypothesized to result from decreased ureide catabolism in the leaf. We showed recently that Asparagine (Asn) chelates Mn ions, which are the co-factor of the enzyme allantoate amidohydrolase, and as a result may cause an inhibition of ureide breakdown in the shoot. These data are consistent with the hypothesis that Asn would be a signal for the feedback inhibition of N 2 fixation. N 2 fixation / drought stress / feedback / ureides / soybean Résumé -Régulation « feedback » de la fixation symbiotique de N 2 sous déficit hydrique. Une large variabilité génétique a été mise en évidence parmi les espèces et cultivars de légumineuses pour la sensibilité de la fixation de N 2 au déficit hydrique. Les espèces de légumineuses qui transportent l'azote sous forme d'uréides se sont avérées plus sensibles que les espèces à amides. Il en a été déduit qu'un mécanisme de régulation de type « feedback » impliquant les uréides serait responsable de l'inhibition de la fixation de N 2 par déficit hydrique. Des résultats expérimentaux montrant une inhibition de l'activité nitrogénase par l'application d'uréides exogènes constituent une preuve supplémentaire en faveur de l'hypothèse de régulation « feedback ». Le mécanisme physiologique responsable de l'accumulation des uréides est supposé résulter d'une diminution du catabolisme foliaire des uréides, mais la nature exacte de la molécule chimique impliquée dans le signal reste encore inconnue. Nous avons montré récemment que l'asparagine (Asn) pourrait induire une inhibition de la dégradation des uréides dans les feuilles, et par conséquent, leur accumulation dans les différents tissus de la plante. Ces résultats soutiennent l'hypothèse de l'intervention de Asn comme signal de régulation du métabolisme des uréides et de la fixation symbiotique de N 2 sous déficit hydrique.

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“…The sucrose concentration was determined according to the manual "Methods of Biochemical Analysis" published by Boehringer Mannheim GmbH in 1989 (Mannheim, Germany). Nitrate was determined as described in Hartwig et al [13].…”

Section: Chemical Analysismentioning

confidence: 99%

“…There are indications that nitrogenase activity may be down-regulated after defoliation as a result of a temporarily reduced N sink in the plant [13]. Thus this study was conducted to test the hypothesis of an N feedback mechanism that regulates nitrogenase activity after defoliation.…”

Section: Introductionmentioning

confidence: 99%

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Increase in the concentrations of amino acids in the vascular tissue of white clover and white lupin after defoliation: an indication of a N feedback regulation of symbiotic N₂ fixation

Hartwig

Trommler

2001

Agronomie

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Abstract -Defoliation, particularly experienced by pasture and forage legumes, is associated with a fast and dramatic decrease in the nitrogenase activity (C 2 H 2 reduction, H 2 evolution in Ar/O 2 ). Since the plant's N demand is temporarily reduced after defoliation, the nitrogenase activity may be down-regulated through a N feedback mechanism. To test this hypothesis, the concentrations of free amino acids in the xylem of white clover and in the phloem of white lupin were measured before and after defoliation. The concentrations of free asparagine, glutamine and aspartate were the highest of all the amino acids before defoliation. The concentrations of these amino acids increased three-fold in the xylem of white clover and two-fold in the phloem of white lupin within one to three hours after defoliation. The results are consistent with the concept of a N feedback mechanism that regulates nitrogen fixation in legume plants, in which free amino acids, cycling in the vascular tissue, act as trigger molecules. Trifolium repens / Lupinus albus / xylem / phloem / nitrogen feedbackRésumé -Accroissement de la concentration d'acides aminés dans le tissu vasculaire du trèfle blanc et du lupin blanc après défoliation : une indication de la régulation par rétroaction de la fixation symbiotique d'azote. La défoliation subie plus particulièrement par les légumineuses fourragères pâturées ou fauchées, est suivie par une décroissance rapide et spectaculaire de l'activité de la nitrogénase (réduction de C 2 H 2 , évolution de H 2 dans Ar/O 2 ). Puisque la demande d'azote de la plante est temporairement réduite après la défoliation, l'activité de la nitogénase devrait être abaissée grâce à un mécanisme de rétroaction de l'azote. Pour tester cette hypothèse, la concentration de trois acides aminés dans la xylème du trèfle blanc et dans le phloème du lupin blanc a été mesurée avant et après la défoliation. La concentration de l'asparagine de la glutamine et de l'aspartate libres était la plus élevée de toutes celles des acides aminés avant la défoliation. Elles ont triplé dans le xylème du trèfle blanc et doublé dans le phloème du lupin blanc dans une période comprise entre une et trois heures après la défoliation. Ces résultats sont en bon accord avec le concept d'un mécanisme de rétroaction de l'azote qui régule la fixation de l'azote dans les légumineuses, dans lequel les acides aminés libres, circulant dans le tissu vasculaire, agissent comme des molécules de déclenchement.

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The nitrogen-sink is involved in the regulation of nitrogenase activity in white clover after defoliation

Cited by 7 publications

References 0 publications

Genotypic difference in the short-term response of nitrogenase activity (C₂H₂ reduction) to salinity and oxygen in the common bean

Genotypic difference in the short-term response of nitrogenase activity (C₂H₂ reduction) to salinity and oxygen in the common bean

Feedback regulation of symbiotic N₂ fixation under drought stress

Increase in the concentrations of amino acids in the vascular tissue of white clover and white lupin after defoliation: an indication of a N feedback regulation of symbiotic N₂ fixation

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The nitrogen-sink is involved in the regulation of nitrogenase activity in white clover after defoliation

Cited by 7 publications

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Genotypic difference in the short-term response of nitrogenase activity (C2H2 reduction) to salinity and oxygen in the common bean

Genotypic difference in the short-term response of nitrogenase activity (C2H2 reduction) to salinity and oxygen in the common bean

Feedback regulation of symbiotic N2 fixation under drought stress

Increase in the concentrations of amino acids in the vascular tissue of white clover and white lupin after defoliation: an indication of a N feedback regulation of symbiotic N2 fixation

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Genotypic difference in the short-term response of nitrogenase activity (C₂H₂ reduction) to salinity and oxygen in the common bean

Genotypic difference in the short-term response of nitrogenase activity (C₂H₂ reduction) to salinity and oxygen in the common bean

Feedback regulation of symbiotic N₂ fixation under drought stress

Increase in the concentrations of amino acids in the vascular tissue of white clover and white lupin after defoliation: an indication of a N feedback regulation of symbiotic N₂ fixation