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NH 3 /NH 4 + ammonia/um -3 N 2 dinitrogen 0 N 2 O nitrous oxide +1 NO nitric oxide +2

Nitrogen has to be reduced. NH 3 /NH 4 + ammonia/um -3 N 2 dinitrogen 0 N 2 O nitrous oxide +1 NO nitric oxide +2 NO 2 - nitrite +3 NO 2 nitrogen dioxide +4 NO 3 - nitrate +5. + N fertilizer. - N fertilizer. nitrification. denitrification.

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NH 3 /NH 4 + ammonia/um -3 N 2 dinitrogen 0 N 2 O nitrous oxide +1 NO nitric oxide +2

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  1. Nitrogen has to be reduced NH3/NH4+ ammonia/um -3 N2 dinitrogen 0 N2O nitrous oxide +1 NO nitric oxide +2 NO2- nitrite +3 NO2 nitrogen dioxide +4 NO3- nitrate +5 + N fertilizer - N fertilizer

  2. nitrification denitrification Soil nitrate is lost by denitrification Ammonium is lost by nitrification

  3. Examples of N containing compounds

  4. Comparison of metabolism

  5. The nitrogenase enzyme The metal cofactors are oxygen labile

  6. Symbiotic N fixation N-deficiency induces nodules (new organ) 3X pea 7X pea See table 16.4 for specific symbiosis of legumes

  7. New organ is produced Communication between bacteria and plants contributes to specificity

  8. symbiosomes Bacteria also differentiate to establish symbiosis

  9. GS-GOGAT cycle Asn, Gln, ureides transported through xylem diCOOH acid in, gln out

  10. Purine synthesis is turned on by NH3 Purine degradation is developmentally determined

  11. Nitrate uptake and reduction Taken up in roots but also leaves Transport driven by H+ gradient H+ gradient established by ATP hydrolysis

  12. Regulation of nitrate uptake depending on availability

  13. Identification of a mutant in nitrate uptake Chlorate resistant plant

  14. After uptake, nitrate is reduced to nitrite first committed step NO3- + NADPH + H+ NO2- + NADP+ + H2O Nitrate reductase is in cytosol has heme, FAD and MoCo Dimers/tetramers -10 mV -272 mV -160 mV Domains combined to form enzyme?

  15. Nitrite is then reduced to ammonia in the plastid NO2- + 6 Fdred + 8 H+ NH4+ + 6 Fdox + 2 H2O NiR is regulated coordinately with NR at tx level From photosynthesis or from NADPH in colorless plastids NADPH + 2 Fdox NADP+ + 2 Fdred + H+ 60-70 kDa with two domains

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