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1. Nusrat Jahan Shimmi
ID: 1502036
Faculty of Agriculture
Sylhet Agricultural University

3. The process by which free nitrogen from the air is
combined with other elements to form organic
compounds that plants can use as nutrients.
Cyanobacteria and certain other
forms of bacteria,especially those
that live in the roots of legumes,
convert gaseous , nitrogen
into organic compounds.
The conversion of nitrogen
gas to nitrates by some
bacteria.

11. 1. Rhizobia attracted to
root
2. Rhizobia attach to root
hairs
3. Root hair curling
4. Infection thread
formation

12. 5. Root cortical cell
division
6. Rhizobia invade
cortical cells
7. The nodule grows
8. Fully functional
nodule

13. Biological nitrogen fixation was discovered by the German
agronomist Hermann Hellriegel and Dutch microbiologist
Martinus Beijerinck.
Biological nitrogen fixation can be represented by the
following equation, in which two moles of ammonia are
produced from one mole of nitrogen gas, at the expense
of 16 moles of ATP and a supply of electrons and protons
(hydrogen ions):
N2 + 8H+ + 8e– + 16 ATP = 2NH3 + H2 + 16ADP + 16 Pi
This reaction is performed exclusively by prokaryotes (the
bacteria and related organisms), using an enzyme complex
termed Nitrogenase. This enzyme consists of two proteins
– an iron protein and a molybdenum-iron protein.

14. Nitrogen fixing bacteria (Rhizobium) that fix atmospheric Nitrogen

15.  Glucose-6-phosphate acts as a electron donor
 Glucose-6-phosphate is converted to
phosphogluconic acid
 NADPH donates electrons to ferrodoxin. Protons
released and ferrodoxin is reduced
 Reduced ferrodoxin acts as electron carrier.
Donate electron to Fe-protein to reduce it.
Electrons released from ferrodoxin thus oxidized
Sucrose
(synthesize
d in leaves)
Sucrose (
in roots )
Glucose
and
fructose
Glucose-6-
phosphate

16.  Reduced Fe-protein combines with ATP in the
presence of Mg +2
 Second sub unit is activated and reduced
 It donates electrons to N2 to NH3
 Enzyme set free after complete reduction of
N2 to NH3