caa a22 4500 47711198X CHVBK 20180405111611.0 cr unu---uuuuu 170330e19960501xx s 000 0 eng 10.1007/BF00011003 doi (NATIONALLICENCE)springer-10.1007/BF00011003 Denitrification in lucerne nodules is not involved in nitrite detoxification [Elektronische Daten] [J. García-Plazaola, C. Arrese-Igor, A. González, P. Aparicio-Tejo, J. Becerril] Dissimilatory reduction of ionic nitrogen oxides to gaseous forms such as nitrous oxide or nitrogen can be carried out by free living or symbiotic forms of some strains of Rhizobium meliloti. In this paper we investigate whether bacteroid denitrification plays a role in the alleviation of the inhibitory effects of nitrate on nitrogen fixation both in bacteroid incubations as in whole nodules. The presence of a constitutive nitrate reductase (NR) activity in isolated bacteroids caused nitrite accumulation in the incubation medium, and acetylene reduction activity in these bacteroids was progressively inhibited, since nitrite reductase (NiR) activity was unable to reduce all the nitrite produced by NR and denitrification occurred slowly. Even nodules infiltrated with nitrate and nitrite failed to increase gaseous forms of nitrogen substantially, indicating that nitrite availability was not limiting denitrification by bacteroids. In spite of the low rates of bacteroidal denitrification, the effect of nodule denitrification on the inhibition of nitrogen fixation by nitrate in whole plants was tested. For that purpose, lucerne plants (Medicago sativa L. cv. Aragon) were inoculated with two Rhizobium meliloti strains: 102-F-65 (non denitrifying) and 102-F-51 (a highly denitrifying strain). After a seven days nitrate treatment, both strains showed the same pattern of inhibition, and it occurred before any nitrate or nitrite accumulation within the nodules could be detected. This observation, together with the lack of alleviation of the ARA inhibition in the denitrifying strain, and the limited activity of dissimilatory nitrogen reduction present in these bacteroids, indicate a role other than nitrite detoxification for denitrification in nodules under natural conditions. Kluwer Academic Publishers, 1996 denitrification nationallicence lucerne nationallicence Medicago sativa nationallicence nitrite detoxification nationallicence Rhizobium meliloti nationallicence García-Plazaola J. Department of Plant Biology and Ecology, University of the Basque Country/EHU, Aptd 644, E-48080, Bilbao, Spain aut Arrese-Igor C. Department of Environmental Sciences, Public University of Navarra, Campus de Arrosadia, E-31006, Pamplona, Spain aut González A. Department of Environmental Sciences, Public University of Navarra, Campus de Arrosadia, E-31006, Pamplona, Spain aut Aparicio-Tejo P. Department of Environmental Sciences, Public University of Navarra, Campus de Arrosadia, E-31006, Pamplona, Spain aut Becerril J. Department of Plant Biology and Ecology, University of the Basque Country/EHU, Aptd 644, E-48080, Bilbao, Spain aut Plant and Soil Kluwer Academic Publishers; gopher://gopher.wkap.nl 182/1(1996-05-01), 149-155 0032-079X 182:1<149 1996 182 11104 https://doi.org/10.1007/BF00011003 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00011003 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- García-Plazaola J. Department of Plant Biology and Ecology, University of the Basque Country/EHU, Aptd 644, E-48080, Bilbao, Spain aut NATIONALLICENCE 700 1- Arrese-Igor C. Department of Environmental Sciences, Public University of Navarra, Campus de Arrosadia, E-31006, Pamplona, Spain aut NATIONALLICENCE 700 1- González A. Department of Environmental Sciences, Public University of Navarra, Campus de Arrosadia, E-31006, Pamplona, Spain aut NATIONALLICENCE 700 1- Aparicio-Tejo P. Department of Environmental Sciences, Public University of Navarra, Campus de Arrosadia, E-31006, Pamplona, Spain aut NATIONALLICENCE 700 1- Becerril J. Department of Plant Biology and Ecology, University of the Basque Country/EHU, Aptd 644, E-48080, Bilbao, Spain aut NATIONALLICENCE 773 0- Plant and Soil Kluwer Academic Publishers; gopher://gopher.wkap.nl/ 182/1(1996-05-01), 149-155 0032-079X 182:1<149 1996 182 11104 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer