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Titre :
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Photoassimilate partitioning in nodulated soybean III. The effect of changes in nodule activity shows that carbon supply to the nodule is not linked to nodule nitrogen metabolism
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Auteurs :
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K. Walsh ;
M. Thorpe ;
P. Minchin
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Type de document :
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article/chapitre/communication
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Année de publication :
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1998
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Format :
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1827-1834
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Langues:
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= Anglais
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Mots-clés:
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C-11
;
nitrogen fixation
;
nodule
;
photoassimilate partitioning
;
soybean
;
Repartition d'assimilats
;
Fixation symbiotique
;
Nodosite
;
Marquage isotopique
;
Azote
;
Carbone
;
Relation source puits
;
Glycine max
;
Leguminosae
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Résumé :
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The hypothesis that photoassimilate partitioning to the soybean nodule is controlled by the rate of N export (via an effect on the turgor of the unloading pathway) was tested. Cessation of N-2 fixation due to exposure of the nodulated root to Ar:O-2 for over 3 h did not affect the partitioning of photoassimilate to the nodule. In contrast, anaerobic conditions (100% N-2) resulted in a temporary cessation or marked slowing of carbon import into the nodule and root organs, reflecting an O-2 requirement of the unloading process. Carbon accumulation by the nodulated root was less affected by a rhizosphere treatment of 2% O-2, although partitioning was decreased over a period of hours. Treatment with 100% O-2 also caused an immediate diversion of photoassimilate from the root to the shoot system, although the extent of this diversion was variable. Treatment with stepped increases in O-2 did not affect partitioning. It is concluded that the unloading kinetics of the nodule were not disturbed by changes in nodule N metabolism, and therefore that control of assimilate partitioning to the nodule is not influenced by a turgor mechanism involving a balance between the primary export and import solutes. However, photoassimilate import was matched to the respiratory demand of the root system.
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Source :
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Journal of Experimental Botany - 0022-0957, vol. 49, n° 328
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