title: The activity of nodules of the supernodulating mutant Mtsunn is not limited by photosynthesis under optimal growth conditions.
abstract: Legumes match the nodule number to the N demand of the plant. When a mutation in the regulatory mechanism deprives the plant of that ability, an excessive number of nodules are formed. These mutants show low productivity in the fields, mainly due to the high carbon burden caused through the necessity to supply numerous nodules. The objective of this study was to clarify whether through optimal conditions for growth and CO2 assimilation a higher nodule activity of a supernodulating mutant of Medicago truncatula (M. truncatula) can be induced. Several experimental approaches reveal that under the conditions of our experiments, the nitrogen fixation of the supernodulating mutant, designated as sunn (super numeric nodules), was not limited by photosynthesis. Higher specific nitrogen fixation activity could not be induced through short- or long-term increases in CO2 assimilation around shoots. Furthermore, a whole plant P depletion induced a decline in nitrogen fixation, however this decline did not occur significantly earlier in sunn plants, nor was it more intense compared to the wild-type. However, a distinctly different pattern of nitrogen fixation during the day/night cycles of the experiment indicates that the control of N2 fixing activity of the large number of nodules is an additional problem for the productivity of supernodulating mutants.
authors.affiliation: Department for Crop Science, Section for Plant Nutrition and Crop Physiology, Faculty of Agriculture, University of Goettingen, Carl-Sprengel-Weg 1, Goettingen 37075, Germany. rcabeza@u.uchile.cl.
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Cabeza
authors.affiliation: Department for Crop Science, Section for Plant Nutrition and Crop Physiology, Faculty of Agriculture, University of Goettingen, Carl-Sprengel-Weg 1, Goettingen 37075, Germany. alingne@agr.uni-goettingen.de.
authors.forename: Annika
authors.initials: A
authors.lastname: Lingner
authors.affiliation: Department for Crop Science, Section for Plant Nutrition and Crop Physiology, Faculty of Agriculture, University of Goettingen, Carl-Sprengel-Weg 1, Goettingen 37075, Germany. rebecca.liese@biologie.uni-goettingen.de.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Liese
authors.affiliation: Signaling Pathway Research Unit, RIKEN Center for Sustainable Resource Science, 1-7-22, Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan. s.sulieman@psc.riken.jp.
authors.forename: Saad
authors.initials: S
authors.lastname: Sulieman
authors.affiliation: Institute for Applied Plant Nutrition, Faculty of Agriculture, University of Goettingen, Carl-Sprengel-Weg 1, Goettingen 37075, Germany. msenbay@uni-goettingen.de.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Senbayram
authors.affiliation: Institute for Applied Plant Nutrition, Faculty of Agriculture, University of Goettingen, Carl-Sprengel-Weg 1, Goettingen 37075, Germany. mtraenk@gwdg.de.
authors.forename: Merle
authors.initials: M
authors.lastname: Tränkner
authors.affiliation: Department for Crop Science, Section for Plant Nutrition and Crop Physiology, Faculty of Agriculture, University of Goettingen, Carl-Sprengel-Weg 1, Goettingen 37075, Germany. klaus.dittert@agr.uni-goettingen.de.
authors.forename: Klaus
authors.initials: K
authors.lastname: Dittert
authors.affiliation: Department for Crop Science, Section for Plant Nutrition and Crop Physiology, Faculty of Agriculture, University of Goettingen, Carl-Sprengel-Weg 1, Goettingen 37075, Germany. jschulz2@gwdg.de.
authors.forename: Joachim
authors.initials: J
authors.lastname: Schulze
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry / Q000378:metabolism; D046913:Medicago truncatula / Q000254:growth & development / Q000378:metabolism*; D009584:Nitrogen / Q000737:chemistry / Q000378:metabolism; D009586:Nitrogen Fixation; D010758:Phosphorus / Q000737:chemistry / Q000378:metabolism; D010788:Photosynthesis; D018520:Plant Shoots / Q000378:metabolism; D053204:Root Nodules, Plant / Q000378:metabolism
chemical_list: D002245:Carbon Dioxide; D010758:Phosphorus; D009584:Nitrogen
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