title: Long-term non-invasive and continuous measurements of legume nodule activity.
abstract: Symbiotic nitrogen fixation is a process of considerable economic, ecological and scientific interest. The central enzyme nitrogenase reduces H(+) alongside N2 , and the evolving H2 allows a continuous and non-invasive in vivo measurement of nitrogenase activity. The objective of this study was to show that an elaborated set-up providing such measurements for periods as long as several weeks will produce specific insight into the nodule activity's dependence on environmental conditions and genotype features. A system was developed that allows the air-proof separation of a root/nodule and a shoot compartment. H2 evolution in the root/nodule compartment can be monitored continuously. Nutrient solution composition, temperature, CO2 concentration and humidity around the shoots can concomitantly be maintained and manipulated. Medicago truncatula plants showed vigorous growth in the system when relying on nitrogen fixation. The set-up was able to provide specific insights into nitrogen fixation. For example, nodule activity depended on the temperature in their surroundings, but not on temperature or light around shoots. Increased temperature around the nodules was able to induce higher nodule activity in darkness versus light around shoots for a period of as long as 8 h. Conditions that affected the N demand of the shoots (ammonium application, Mg or P depletion, super numeric nodules) induced consistent and complex daily rhythms in nodule activity. It was shown that long-term continuous measurements of nodule activity could be useful for revealing special features in mutants and could be of importance when synchronizing nodule harvests for complex analysis of their metabolic status.
authors: Section for Plant Nutrition and Crop Physiology, Faculty of Agriculture, Department of Crop Science, University of Goettingen, Carl-Sprengel-Weg 1, Goettingen, 37075, Germany; Facultad de Ciencias Agronómicas, Departamento de Ingeniería y Suelos, Universidad de Chile, Av. Santa Rosa 11315, La Pintana, Santiago, Chile.
authors: Ricardo A
authors: RA
authors: Cabeza
authors: Rebecca
authors: R
authors: Liese
authors: Stephanie A
authors: SA
authors: Fischinger
authors: Saad
authors: S
authors: Sulieman
authors: Ulrike
authors: U
authors: Avenhaus
authors: Annika
authors: A
authors: Lingner
authors: Hans
authors: H
authors: Hein
authors: Beke
authors: B
authors: Koester
authors: Vanessa
authors: V
authors: Baumgarten
authors: Klaus
authors: K
authors: Dittert
authors: Joachim
authors: J
authors: Schulze
mesh_terms: D002940:Circadian Rhythm; D046913:Medicago truncatula / Q000502:physiology*; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000032:analysis*; D053204:Root Nodules, Plant / Q000502:physiology*; D013696:Temperature
chemical_list: D009591:Nitrogenase
keywords: CO2 concentration; H2 evolution; Medicago truncatula; N2 fixation; Nodule; legumes; nitrogen fixation; nitrogenase; technical advance