Nitrogen fixation

About: Nitrogen fixation is a research topic. Over the lifetime, 7940 publications have been published within this topic receiving 232921 citations. The topic is also known as: GO:0009399.

Iron-deficiency specifically limits nodule development in peanut inoculated with Bradyrhizobium sp

Abstract: Severely iron-deficient peanuts (Arachis hypogaaea L.) grown on calcareous soils in central Thailand failed to nodulate until given foliar iron applications. Glasshouse experiments were conducted on two cultivars (Tainan 9 and Robut 33-1) to identify which stage of the nodule symbiosis was most sensitive to iron-deficiency. Iron-deficiency did not limit growth of soil or rhizosphere populations of peanut liradyrhizobium. Similar numbers of root nodule initials formed in the roots of both control and iron-sprayed plants, showing that iron-deficiency did not directly affect root infection and nodule initiation. Plants sprayed with iron produced greater numbers of excisable nodules and carried a greater nodule mass than untreated plants. Five days after iron application, nodules on sprayed plants of CV. Tainan 9 contained 200-fold higher bacteroid numbers per unit weight and 14-fold higher concentrations of leghaemoglobain. The onset of nitrogenase activity was also delayed by iron deficiency in both cultivars. Tainan 9 appeared more sensitive to iron-deficiency than Robut 33-1 in terms of nodule mass produced, but both cultivars showed the same effect of iron-deficiency on nitrogenase activity per plant. It is concluded that the failure of the infecting rhizobia to obtain adequate amounts of iron from the plant results in arrested nodule development and a failure of nitrogen fixation.

Ontogenetic Interactions between Photosynthesis and Symbiotic Nitrogen Fixation in Legumes

Abstract: Photosynthetic data collected from Pisum sativum L. and Phaseolus vulgaris L. plants at different stages of development were related to symbiotic N2 fixation in the root nodules. The net carbon exchange rate of each leaf varied directly with carboxylation efficiency and inversely with the CO2 compensation point. Net carbon exchange of the lowest leaves reputed to supply fixed carbon to root nodules declined in parallel with H2 evolution from root nodules. The decrease in H2 evolution also coincided with the onset of flowering but preceded the peak in N2 fixation activity measured by acetylene-dependent ethylene production. A result of these changes was that the relative efficiency of N2 fixation in peas increased to 0.7 from an initial value of 0.4. The data reveal that attempts to identify photosynthetic contributions of leaves to root nodules will require careful timing and suggest that the relative efficiency of N2 fixation may be influenced by source-sink relationships.

Developmental aspects of the Rhizobium-legume symbiosis.

Abstract: In the plant kingdom a great variety of pathogenic, saprophytic and symbiotic interactions between plants and microorganisms occur, and several of these interactions have been the subject of intensive research. One of the best studied interactions is the symbiosis of Rhizobium, Bradyrhizobium or Azorhizobium bacteria with legume plants, which results in the formation of root nodules, in which bacteria are able to fix atmospheric nitrogen into ammonia. This process of symbiotic N2 fixation is the major naturally occurring mechanism by which nitrogen is reduced and the ecological and agricultural importance of this process has been an important incentive to study this plant-microbe relation. The process of symbiotic N2 fixation has been discussed in several recent reviews [33].

N2-Fixing Microbial Consortia Associated with the Ice Cover of Lake Bonney, Antarctica.

Abstract: Nitrogen (N) availability is a key nutritional factor controlling microbial production in Antarctic freshwater and soil habitats Since there are no significant sources of biologically available N entering these ecosystems, nitrogen fixation may be a major source of ``new'' N supporting primary and secondary production The role of N2 fixation was examined in cyanobacteria-dominated microbial aggregates embedded in the permanent ice cover of Lake Bonney, McMurdo Dry Valley (Victoria Land) lakes area, and in cyanobacterial mats found in soils adjacent to the ice edge Nitrogenase activity was extremely low compared to temperate and tropical systems, but N2 fixation was found at all study sites N2 fixation occurred under both dark and light conditions, indicating the potential involvement of both phototrophic and heterotrophic diazotrophs Nitrogenase activity measurements (acetylene reduction assay) and molecular characterization (PCR amplification of nifH fragments) demonstrated a diverse and periodically active (when liquid water is present) diazotrophic community in this arid, nutrient-limited environment As a result of the close proximity to other microorganisms and the nutritional constraints of this environment, these diazotrophs may be involved in mutually beneficial consortial relationships that enhance their growth when water is available

Characterization of Rhizobium from root nodules of leguminous trees growing in alkaline soils

Abstract: High temperature, pH, and salt stresses in tropical alkaline soils limit nodulation and dinitrogen fixation by strains of Rhizobium from the root nodules of nitrogen fixing trees (NFTs). This study...