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Nitrogen fixation and photosynthetic oxygen evolution ..

cyanobacteria; differentiation; nitrogen fixation; pattern formation; cell communication

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Simultaneous Nitrogen-Fixation and Photosynthesis in Trichodesmium

For example, Azospirillum species have been shown to fix nitrogen when growing in the root zone (rhizosphere) or tropical grasses, and even of maize plants in field conditions.

Biological fixation of nitrogen is done by specialized organisms like microorganisms like , , and .

In a symbiotic relationship with the soil bacteria known as 'rhizobia', legumes form nodules on their roots (or stems, see figure below) to 'fix' nitrogen into a form usable by plants (and animals). The process of biological nitrogen fixation was discovered by the Dutch microbiologist Martinus Beijerinck. Rhizobia (e.g., Rhizobium, Mesorhizobium, Sinorhizobium) fix atmospheric nitrogen or dinitrogen, N2, into inorganic nitrogen compounds, such as ammonium, NH4+, which is then incorporated into amino acids, which can be utilized by the plant. Plants cannot fix nitrogen on their own, but need it in one form or another to make amino acids and proteins. Because legumes form nodules with rhizobia, they have high levels of nitrogen available to them. Their abundance of nitrogen is beneficial not only to the legumes themselves, but also to the plants around them. There are other sources of nitrogen in the soil, but are not always provided at the levels required by plants, making the symbiotic relationship between legumes and rhizobia highly beneficial. In return for the fixed nitrogen that they provide, the rhizobia are provided shelter inside of the plant's nodules and some of the carbon substrates and micronutrients that they need to generate energy and key metabolites for the cellular processes that sustain life (Sprent, 2001). Nodulation and nitrogen fixation by rhizobia is not exclusive to legumes; rhizobia form root nodules on Parasponis Miq., a genus of five species in the Ulmaceae (see 'Rosales').

Plant Nutrition - Photosynthesis | Nitrogen Cycle, Fixation

Foster RA, Kuypers MMM, Vagner T, et al. (2011) Nitrogen fixation and transfer in open ocean diatom‐cyanobacterial symbioses. The ISME Journal 5: 1484–1493.

Fredriksson C, Malin G, Siddiqui PJA and Bergman B (1998) Aerobic nitrogen fixation is confined to a subset of cells in the non‐heterocystous cyanobacterium Symploca PCC 8002. New Phytologist 140: 531–538.

The Relationship Between Photosynthesis and Nitrogen Fixation * E

Under nitrogen fixing conditions the two cell types rely on each other and exchange metabolites and signalling molecules, presumably via protein‐complex‐mediated cell‐to‐cell contact or the continuous periplasmic space that surrounds all cells of the multicellular filament.

Gallon JR and Hamadi AF (1984) Studies on the effects of oxygen on acetylene reduction (nitrogen fixation) in Gloeothece sp. ATCC 27152. Journal of General Microbiology 130: 495–503.

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  • Nitrogen Fixation in Cyanobacteria

    Böhme H (1998) Regulation of nitrogen fixation in heterocyst‐forming cyanobacteria. Trends in Plant Science 3: 346–351.

  • Stal, Lucas J(Dec 2015) Nitrogen Fixation in Cyanobacteria

    Wyatt JT and Silvey JKG (1969) Nitrogen fixation by Gloeocapsa. Science 165: 908–909.

  • Nitrogen fixation and photosynthetic oxygen evolution in ..

    Zehr JP (2011) Nitrogen fixation by marine cyanobacteria. Trends in Microbiology 19: 162–173.

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Mini-review Nitrogen fixation and photosynthetic oxygen ..

Alfalfa (Medicago sativa L.) plants were inoculated with Sinorhizobium meliloti Tn-5 mutants featuring various nitrogen-fixing effectiveness and then grown in sand culture to study relations between CO2 exchange, plant productivity, and nitrogen fixation. At the flowering stage, the relationship between nitrogen fixation and photosynthesis of whole alfalfa plants was described with the logarithmic curve. At the same stage of plant development, a close relationship was observed between nitrogen fixation rate and plant weight; this relationship showed a trend toward saturation at high rates of nitrogen fixation. The increase in nitrogenase activity of root nodules was accompanied by stimulation of root respiration; the relation of respiration to nitrogen-fixing activity was manifested stronger than its relation to the total root weight. It is concluded that highly effective strains of root nodule bacteria can realize their potential only in combination with complementary plant genotypes featuring active photosynthesis that provides a balanced supply of assimilates for both the symbiotic apparatus and growth processes in the macrosymbiont.

Nitrogen fixation and nitrogen metabolism - PEOI

Typically, nitrogen-fixing microorganisms do not fix free atmosphericnitrogen to a usable form in one step. Usually one set of organisms converts free nitrogen (N) to ammonia (NH). This ammonia is accompanied by its ammonium ion (NH), which some plants can use. However, mostflowering plants need nitrogen in yet another form, which microorganisms provide byconverting the ammonia to usable nitrate (NO).

Nitrogen fixation and photosynthesis in high arctic …

Nitrogenase is the enzyme responsible for N2 fixation and allows the organism to live from sunlight, air (carbon dioxide and N2) and some minerals.

Coupling between photosynthesis and nitrogen fixation.

The nitrogen cycle (shown below) describes the series of processes by which the element nitrogen, which makes up about 78% of the Earth’s atmosphere, cycles between the atmosphere and the biosphere. Plants, bacteria, animals, and manmade and natural phenomena all play a role in the nitrogen cycle. The fixation of nitrogen, in which the gaseous form dinitrogen, N2) is converted into forms usable by living organisms, occurs as a consequence of atmospheric processes such as lightning, but most fixation is carried out by free-living and symbiotic bacteria. Plants and bacteria participate in symbiosis such as the one between legumes and rhizobia or contribute through decomposition and other soil reactions. Bacteria like Rhizobium, or the actinomycete Frankia which nodulates members of the plant families Rosaceae and Betulaceae, utilize atmospheric nitrogen and convert it to an inorganic form (usually ammonium, NH4+) that plants can use. The plants then use the fixed nitrogen to produce vital cellular products such as proteins. The plants are then eaten by animals, which also need nitrogen to make amino acids and proteins. Decomposers acting on plant and animal materials and waste return nitrogen back to the soil. Human-produced fertilizers are another source of nitrogen in the soil along with pollution and volcanic emissions, which release nitrogen into the air in the form of ammonium and nitrate gases. The gases react with the water in the atmosphere and are absorbed by the soil with rain water. Other bacteria in the soil are key components in this cycle converting nitrogen containing compounds to ammonia, NH3, nitrates, NO3-, and nitrites, NO2-. Nitrogen is returned back to the atmosphere by denitrifying bacteria, which convert nitrates to dinitrogen gas.

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