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.

Yield of micropropagated sugarcane varieties in different soil types following inoculation with diazotrophic bacteria

Abstract: It is well described that the beneficial interactions between plants and bacteria are genotype and site specific. Brazilian sugarcane varieties can obtain up to 70% of their nitrogen requirement from biological nitrogen fixation (BNF), and this contribution is related to the Brazilian breeding and selection processes, by example of the variety SP70-1143. In this study the effect of two inoculation mixtures containing diazotrophic bacteria in our earlier pot experiment was evaluated with two sugarcane varieties, a known responder, SP70-1143, and a newly selected variety, SP81-3250, to investigate the sugarcane genotype effect and the role of the mixtures. The sugarcane varieties SP70-1143 and SP81-3250 were grown under commercial field conditions at three sites with contrasting soil types: an Alfisol, an Oxisol and an Ultisol that means a low, medium and high natural fertility respectively. The stem yield and BNF contribution in response to bacterial inoculation were influenced by the strain combinations in the inoculum, the plant genotype, and the soil type and nitrogen fertilization, confirming the genetic and environmental influence in PGP-bacteria interactions. Inoculation effects on the BNF contribution and stem yield increased in the variety SP70-1143 grown in the Alfisol without nitrogen fertilization for three consecutive crops, and it was equivalent to the annual nitrogen fertilization. The plants grown in the Oxisol showed small increases in the productivity of the variety SP70-1143, and in the Ultisol the sugarcane plants presented even decreases in the stem productivity due to inoculation with diazotrophic bacteria mixtures. The results demonstrate the feasibility of the inoculation technology using diazotrophic bacteria in micropropagated sugarcane varieties grown in soils with low to medium levels of fertility. In addition, the results also indicated that specific plant – bacteria – environment combinations are needed to harness the full benefits of BNF.

Global Changes in the Transcript and Metabolic Profiles during Symbiotic Nitrogen Fixation in Phosphorus-Stressed Common Bean Plants

Abstract: Phosphorus (P) deficiency is widespread in regions where the common bean (Phaseolus vulgaris), the most important legume for human consumption, is produced, and it is perhaps the factor that most limits nitrogen fixation. Global gene expression and metabolome approaches were used to investigate the responses of nodules from common bean plants inoculated with Rhizobium tropici CIAT899 grown under P-deficient and P-sufficient conditions. P-deficient inoculated plants showed drastic reduction in nodulation and nitrogenase activity as determined by acetylene reduction assay. Nodule transcript profiling was performed through hybridization of nylon filter arrays spotted with cDNAs, approximately 4,000 unigene set, from the nodule and P-deficient root library. A total of 459 genes, representing different biological processes according to updated annotation using the UniProt Knowledgebase database, showed significant differential expression in response to P: 59% of these were induced in P-deficient nodules. The expression platform for transcription factor genes based in quantitative reverse transcriptase-polymerase chain reaction revealed that 37 transcription factor genes were differentially expressed in P-deficient nodules and only one gene was repressed. Data from nontargeted metabolic profiles indicated that amino acids and other nitrogen metabolites were decreased, while organic and polyhydroxy acids were accumulated, in P-deficient nodules. Bioinformatics analyses using MapMan and PathExpress software tools, customized to common bean, were utilized for the analysis of global changes in gene expression that affected overall metabolism. Glycolysis and glycerolipid metabolism, and starch and Suc metabolism, were identified among the pathways significantly induced or repressed in P-deficient nodules, respectively.

The utilization of the Azolla - Anabaena complex as a nitrogen fertilizer for rice

Abstract: Because it contains nitrogen fixing blue-green algae Anabaefa azota in its fronds, AzoZla grows on a nitrogen-free solution, doubles its mass in 3 or 5 days, and accumulates 30 or 40 kg of N/ha in 2 weeks. A calcium or phosphorus deficiency in the Azolla culture solution produces severe deterioration on growth. The optimum solution pH for Azolia is 5.5; a higher pH produces iron deficiency. Azolia is sensitive to a temperature higher than 310C (350 day which causes reddish-brown discoloration and reduces vigor...

Impact of 25 years of inorganic fertilization on diazotrophic abundance and community structure in an acidic soil in southern China

Abstract: Although diazotrophs are important in the nitrogen (N)-cycle and contribute to the pool of plant available N, the population response to long-term inorganic fertilization is largely unknown. Here, we investigated the diazotrophic populations in both the bulk and rhizosphere soils of maize grown in an acidic farmland soil that experienced 25 years of inorganic fertilization. The fertilization regimes included unfertilized control, N fertilizer alone, N fertilizer with quicklime, phosphorus (P) and potassium (K) fertilizers, N + P + K fertilizers, and N + P + K fertilizers with quicklime. Quantitative PCR and high-throughput pyrosequencing of the nifH gene were used to analyze diazotrophic abundance and community composition. All of the fertilizer treatments improved soil nutrient availability, but those without quicklime caused soil acidification. Maize biomasses and nifH copy numbers were significantly lower under N and N + P + K treatments but increased under P + K fertilization. Quicklime applications effectively alleviated the inhibitory effect of N input. Fertilization led to decreases in operational taxonomic unit richness and shifts in diazotrophic community composition. Soil pH and nutrient availability had a cooperative effect on diazotrophic abundance, while soil nutrient availability appeared to be the main factor shaping diazotrophic community structure. Rhizosphere effects increased the nifH gene copy number but did not obviously change the diazotrophic community composition on the current research scale. Overall, the long-term inorganic fertilization affected both diazotrophic abundance and community composition, and the fertilizer treatment had a greater influence than quicklime remediation or crop cultivation on community composition.

Occurrence, physiological and molecular analysis of endophytic diazotrophic bacteria in gramineous energy plants

Abstract: Endophytic diazotrophic bacteria could be isolated from the energy plants Pennisetum purpureum, Miscanthus sinensis, Miscanthus sacchariflorus and Spartina pectinata using semisolid nitrogen free media. Higher levels of diazotrophic bacteria were found if no nitrogen fertilizer was applied. The bacteria were characterized on the basis of typical morphology, physiological tests, and the use of phylogenetic oligonucleotide probes. They belong partially to the species Azospirillum lipoferum and Herbaspirillum seropedicae while others supposedly represent a new species of Herbaspirillum. Using PCR-fingerprinting techniques a limited genetic diversity of these isolates was found which may indicate an adaptation to the specific conditions of the interior of these plants.