Nitrogen fixation is the process by which nitrogen in the atmosphere is converted into nitrogen compounds that can be used by plants. This can occur through non-biological means involving lightning and radiation, or through biological nitrogen fixation. Biological nitrogen fixation is performed by symbiotic and non-symbiotic bacteria and blue-green algae. Symbiotic nitrogen fixation occurs through root nodules formed by legumes via their symbiotic relationship with Rhizobia bacteria, and by some non-leguminous plants with actinomycetes. The bacteria in the nodules produce the nitrogenase enzyme which converts atmospheric nitrogen into ammonia that is used by the plant.

1. NITROGEN FIXATION
Presented By: Muhammad Uzair Siddique

2. NITROGEN GAS
 Transparent
 Odorless
 Diatomic gas
 Triple bond
 78 % by volume in air we breath.

3. ROLE OF NITROGEN IN PLANTS
 Healthy plants contain 3 to 4 percent nitrogen
 Major substance in plants next to water
 Important in plant growth, development and reproduction
 Constituent element of
»Chlorophyll
»Amino acids
»Alkaloids
»Many vitamins
 And the building blocks of protein

4. NITROGEN
FIXATION
The conversion of free
nitrogen into nitrogenous
salts to make it available
for absorption of plants

5. TYPES OF NITROGEN FIXATION
Nitrogen fixation
Non biological Biological
Non - symbiotic Symbiotic

6. NON-BIOLOGICAL NITROGEN FIXATION
 Also known as electro chemical or photochemical nitrogen fixation.
 The conversion of atmospheric nitrogen into NO2, NO3, NH3 with help of
`lightning and radiation.
 These lightning and radiations splits the molecular nitrogen into nitrogen
atom.
 It then combines with hydrogen or oxygen of atmospheric water forming the
ammonia or nitric oxides or nitrous oxides.
 These oxides then get hydrated and form nitrous and nitric acid, these acids
and ammonia is washed of along with rain into the soil. There these acids
combine with metallic ions to form metallic nitrites or nitrates.

7. BIOLOGICAL NITROGEN FIXATION
Biological nitrogen fixation (BNF) is the term used for a process in which
nitrogen gas (N2) from the atmosphere is incorporated into the tissue of
certain plants with the help of micro-organisms
BNF
Symbiotic Non-Symbiotic

8. NON SYMBIOTIC NITROGEN FIXATION
 The fixation of free nitrogen of the soil by all the microorganisms living freely
or outside the plant cell is called non-symbiotic biological Nitrogen fixation.
 It is performed by the aerobic and anaerobic bacteria and blue green algae

9. SYMBIOTIC NITROGEN FIXATION
Fixation of free nitrogen by micro-organisms in soil living
symbiotically inside the plants
Three categories
Nodule formation in leguminous plants
Nodule formation in non-leguminous plants
Non nodulation

10. NITROGEN FIXATION THROUGH NODULE
FORMATION IN NON-LEGUMINOUS PLANTS
 There are many plants belonging non- Leguminous families, specially
shrubs and plants produce root nodules. i.e. by actinomycetes in
angiosperms

11. NITROGEN FIXATION THROUGH NON-
NODULATION
 In some plants root nodules are not formed but symbiotic nitrogen fixation
takes place.
 Example:- Lichens live as symbiotic relationship with photosynthetic
cyanobacteria

12. NODULE FORMATION IN LEGUMINOUS PLANTS
 2500 species of family leguminosae ( Cicer arientium, Pisum,
Cajanus, Arachis) produce root nodules with Rhizobium spp.
 Root nodules are formed due to infection of Rhizobium
 Free living bacteria growing near root of legumes unable to fix
nitrogen in free condition
 Roots of the legumes secrete some growth factors helps in fast
multiplication of bacteria (E.g.) Pisum sativum secretes
carbohydrate containing Lectins over their surface

13.  Rhizobial cells have carbohydrate receptor on their surface
 Lectins interact with the carbohydrate receptor of rhizobial cells
 This helps in recognition and attachment of rhizobial cells
 Bacteria enter the roots through soft infected root hairs
 Tips are deformed and curved
 Tubular infection thread is formed in the root hair cell and bacteria enters into it

15.  After entry, new cell wall is formed and Bacteria starts multiplication.
 It grows much and reaches the inner layers of cortex
 It induces the cortical cells to multiply which result in the formation of nodule
on the surface
 The bacterial cells multiplies and colonize in the multiplying host cells
 After host cells are completely filled, bacterial cells becomes dormant
 In response to the roots being colonized by nitrogen-fixing bacteria a reddish
pigment leghaemoglobin is produced in cytoplasm of host cells

17.  Nitrogenous compounds synthesized is translocated through vascular tissues
 The rhizobia create ammonia from nitrogen in the air, which is used by the plant
to create amino acids and nucleotides. The plant provides the bacteria with
sugars.

18. NITROGENASE AND HYDROGENASE
ENZYME
Nitrogenase
 Plays key role
 Active in anaerobic condition
 Nitrogenase is used to separate nitrogen gas, N2, and transforms it into
ammonia, NH3 in the reaction
Hydrogenase
• Hydrogen produced is catalyzed into protons and electrons by
hydrogenase

19. H2 2H+ + 2e-
N2 + 6H+ + 6e- 2NH3

21. CROP LB/ACRE NITROGEN
Alfalfa 196
Ladino Clover 178
Sweet Clover 116
Red Clover 112
White Clover 103
Soybeans 98
Cowpeas 89
Lespedeza 85
Vetch 80
Garden Peas 71
Winter Peas 54
Peanuts 42

22. ADVANTAGES
 Nitrogen is a very essential component of photosynthesis process
 Plants with efficient nitrogen would have better seeds and better fruiting
 Nitrogen is also very essential in metabolic activities in plants
 In humans Nitrogen is important, as it is used to make proteins, good
immune system and even making hormones
 It is also a part of DNA

23. DISADVANTAGES
Slower process in producing fertility
Increases a possible source of vegetative competition among
other crop species