Soil organic matter has long been recognized as one of the most important components in maintaining soil fertility, soil quality, and agricultural sustainability. The soil zone strongly influenced by plant roots, the rhizosphere, plays an important role in regulating soil organic matter decomposition and nutrient cycling. Processes that are largely controlled or directly influenced by roots are often referred to as rhizosphere processes. These processes may include exudation of soluble compounds, water uptake, nutrient mobilization by roots and microorganisms, rhizosphere-mediated soil organic matter decomposition, and the subsequent release of CO2 through respiration. Rhizosphere processes are major gateways for nutrients and water. At the global scale, rhizosphere processes utilize approximately 50% of the energy fixed by photosynthesis in terrestrial ecosystems, contribute roughly 50% of the total CO2 emitted from terrestrial ecosystems, and mediate virtually all aspects of nutrient cycling. Therefore, plant roots and their rhizosphere interactions are at the center of many ecosystem processes. However, the linkage between rhizosphere processes and soil organic matter decomposition is not well understood. Because of the lack of appropriate methods, rates of soil organic matter decomposition are commonly assessed by incubating soil samples in the absence of vegetation and live roots with an implicit assumption that rhizosphere processes have little impact on the results. Our recent studies have overwhelmingly proved that this implicit assumption is often invalid, because the rate of soil organic matter decomposition can be accelerated by as much as 380% or inhibited by as much as 50% by the presence of live roots. The rhizosphere effect on soil organic matter decomposition is often large in magnitude and significant in mediating plant-soil interactions.
he rhizosphere is the narrow region of soil or substrate that is directly influenced by root secretions and associated soil microorganisms known as the root microbiome.
The phyllosphere is a term used in microbiology to refer to the total above-ground portions of plants as habitat for microorganisms.
Soil organic matter has long been recognized as one of the most important components in maintaining soil fertility, soil quality, and agricultural sustainability. The soil zone strongly influenced by plant roots, the rhizosphere, plays an important role in regulating soil organic matter decomposition and nutrient cycling. Processes that are largely controlled or directly influenced by roots are often referred to as rhizosphere processes. These processes may include exudation of soluble compounds, water uptake, nutrient mobilization by roots and microorganisms, rhizosphere-mediated soil organic matter decomposition, and the subsequent release of CO2 through respiration. Rhizosphere processes are major gateways for nutrients and water. At the global scale, rhizosphere processes utilize approximately 50% of the energy fixed by photosynthesis in terrestrial ecosystems, contribute roughly 50% of the total CO2 emitted from terrestrial ecosystems, and mediate virtually all aspects of nutrient cycling. Therefore, plant roots and their rhizosphere interactions are at the center of many ecosystem processes. However, the linkage between rhizosphere processes and soil organic matter decomposition is not well understood. Because of the lack of appropriate methods, rates of soil organic matter decomposition are commonly assessed by incubating soil samples in the absence of vegetation and live roots with an implicit assumption that rhizosphere processes have little impact on the results. Our recent studies have overwhelmingly proved that this implicit assumption is often invalid, because the rate of soil organic matter decomposition can be accelerated by as much as 380% or inhibited by as much as 50% by the presence of live roots. The rhizosphere effect on soil organic matter decomposition is often large in magnitude and significant in mediating plant-soil interactions.
he rhizosphere is the narrow region of soil or substrate that is directly influenced by root secretions and associated soil microorganisms known as the root microbiome.
The phyllosphere is a term used in microbiology to refer to the total above-ground portions of plants as habitat for microorganisms.
Mycorrhiza Biofertilizer is also known as VAM (Myco = Fungal + rrhiza = roots) adheres to plants rhizoids leading to development of hyphae. Hyphae boost development and spreading of white root in to soil leading to significant increase in rhizosphere. These hyphae further penetrate and form arbuscules within the root cortical. VAM fungi form a special symbiotic relationship with roots of plant that can enhance growth and survivability of colonized plants. Mycorrhiza Biofertilizer is very useful in organic farming as well as normal commercial farming
It is a biofertilizer that contains symbiotic Rhizobium bacteria which is the most important nitrogen-fixing organism. These organisms have the ability to drive atmospheric Nitrogen and provide it to plants. It is recommended for crops such as Groundnut, Soybean, Red-gram, Green-gram, Black-gram, Lentil, Cowpea, Bengal-gram and Fodder legumes, etc.
Soils give a mechanical support to plants from which they extract nutrients. soil provides shelters for many animal types, from invertebrates such as worms and insects up to mammals like rabbits, moles, foxes and badgers. It also provides habitats colonised by a staggering variety of microorganisms. This module is about the microbial life in soils.
PHOSPHATE SOLUBILIZERS
INTRODUCTION
Phosphate SOLUBILIZERS are a group of beneficial micro-organisms capable of breaking down of organic and inorganic insoluble phosphorous compounds to soluble P form that can easily be assimilated by plants.
Phosphorous (P) is a major growth-limiting nutrient, Plants acquire phosphorus from soil solution as phosphate anion.
TYPES
MECHANISM
ISOLATION
INOCULANT PRODUCTION
INOCULANT APPLICATION
ROLE OF PHOSPHATE SOLUBILIZERS
Introduction :
Mycorrhizae are mutualistic symbiotic associations formed between the roots of higher plants and fungi.
Fungal roots were discovered by the German botanist A B Frank in the last century (1855) in forest trees such as pine.
In nature approximately 90% of plants are infected with mycorrhizae. 83% Dicots,79% Monocots and 100% Gymnosperms.
Convert insoluble form of phosphorous in soil into soluble form.
Microbial interactions are ubiquitous, diverse, critically important in the function of any biological community.
The most common cooperative interactions seen in microbial systems are mutually beneficial. The interactions between the two populations are classified according to whether both populations and one of them benefit from the associations, or one or both populations are negatively affected.
DEFINITION OF PHYLLOSPHERE
PARTS OF PHYLLOSPHERE
MICROORGANISM OF PHYLLOSPHERE
PHYLLOSPHERE MICROORGANISMS OF STEM (CAULOSPHERE)
PHYLLOSPHERE MICROORGANISMS OF LEAVES(PHYLLOPLANE)
PHYLLOSPHERE MICROORGANISMS OF FLOWER (ANTHOSPHERE)
PHYLLOSPHERE MICROORGANISMS OF FRUIT(CARPOSPHERE)
FACTORS INFLUENCING MICROBIAL GROWTH AND ACTIVITIES
POSITIVE EFFECT OF PHYLLOSPHERE MICROORGANISMS
NEGATIVE EFFECT OF PHYLLOSPHERE MICROORGANISMS
Mycorrhiza Biofertilizer is also known as VAM (Myco = Fungal + rrhiza = roots) adheres to plants rhizoids leading to development of hyphae. Hyphae boost development and spreading of white root in to soil leading to significant increase in rhizosphere. These hyphae further penetrate and form arbuscules within the root cortical. VAM fungi form a special symbiotic relationship with roots of plant that can enhance growth and survivability of colonized plants. Mycorrhiza Biofertilizer is very useful in organic farming as well as normal commercial farming
It is a biofertilizer that contains symbiotic Rhizobium bacteria which is the most important nitrogen-fixing organism. These organisms have the ability to drive atmospheric Nitrogen and provide it to plants. It is recommended for crops such as Groundnut, Soybean, Red-gram, Green-gram, Black-gram, Lentil, Cowpea, Bengal-gram and Fodder legumes, etc.
Soils give a mechanical support to plants from which they extract nutrients. soil provides shelters for many animal types, from invertebrates such as worms and insects up to mammals like rabbits, moles, foxes and badgers. It also provides habitats colonised by a staggering variety of microorganisms. This module is about the microbial life in soils.
PHOSPHATE SOLUBILIZERS
INTRODUCTION
Phosphate SOLUBILIZERS are a group of beneficial micro-organisms capable of breaking down of organic and inorganic insoluble phosphorous compounds to soluble P form that can easily be assimilated by plants.
Phosphorous (P) is a major growth-limiting nutrient, Plants acquire phosphorus from soil solution as phosphate anion.
TYPES
MECHANISM
ISOLATION
INOCULANT PRODUCTION
INOCULANT APPLICATION
ROLE OF PHOSPHATE SOLUBILIZERS
Introduction :
Mycorrhizae are mutualistic symbiotic associations formed between the roots of higher plants and fungi.
Fungal roots were discovered by the German botanist A B Frank in the last century (1855) in forest trees such as pine.
In nature approximately 90% of plants are infected with mycorrhizae. 83% Dicots,79% Monocots and 100% Gymnosperms.
Convert insoluble form of phosphorous in soil into soluble form.
Microbial interactions are ubiquitous, diverse, critically important in the function of any biological community.
The most common cooperative interactions seen in microbial systems are mutually beneficial. The interactions between the two populations are classified according to whether both populations and one of them benefit from the associations, or one or both populations are negatively affected.
DEFINITION OF PHYLLOSPHERE
PARTS OF PHYLLOSPHERE
MICROORGANISM OF PHYLLOSPHERE
PHYLLOSPHERE MICROORGANISMS OF STEM (CAULOSPHERE)
PHYLLOSPHERE MICROORGANISMS OF LEAVES(PHYLLOPLANE)
PHYLLOSPHERE MICROORGANISMS OF FLOWER (ANTHOSPHERE)
PHYLLOSPHERE MICROORGANISMS OF FRUIT(CARPOSPHERE)
FACTORS INFLUENCING MICROBIAL GROWTH AND ACTIVITIES
POSITIVE EFFECT OF PHYLLOSPHERE MICROORGANISMS
NEGATIVE EFFECT OF PHYLLOSPHERE MICROORGANISMS
Nitrogen is important element of life. In importance it comes only next to carbon, hydrogen, and oxygen. The composition of protein, nucleic acid, growth hormones, and vitamins requires Nitrogen. Leaves consist of about 1 to 15% nitrogen of their dry weight but lesser % in another vegetative organ.
• The N2 is present in the atmosphere, in the form of gas. It is about 78%.
• Green plants unable to use this N2 directly in their metabolism. Only some micro-organism can convert this N2 gas directly into organic form.
• The N2 present in the soil is called soil nitrogen. The plants growing in the soil, mainly utilize the soil N2 for their metabolic requirements.
• In the soil the nitrogen is present in the form of nitrate nitrogen (NO3, NO2), ammonia nitrogen (ammonia, ammonium salt), organic nitrogen and molecular nitrogen (N2).
• The converging of the free nitrogen, by natural or physical process is called nitrogen fixation… when any biological system is involved in this process, then it is called as biological nitrogen fixation……
Roles of microbes in nitrogen cycle aritriyaaritriyajana
There are many presentation on nitrogen cycle.but in my case i have to make a ppt on microbes role in nitrogen cycle.so i made it.and then upload it if anyone get help from it i will be pleased. Aritriya Jana(F.F.Sc)
Nitrogen is a universally occurring element in all living beings.
It is a predominant element, present in nucleic acid, alkaloids, some vitamins and chlorophyll pigments of the plants.
Thus, nitrogen plays a very important and fundamental role in metabolism, growth, reproduction, and heredity
• Nutrient cycles referred to as biogeochemical cycles
• Gaseous forms of carbon, oxygen, and nitrogen occur in the atmosphere and cycle globally
• Less mobile elements, including phosphorous, cycle on a more local level
• Still, gains and losses from outside of the ecosystem are generally small when compared to the rate at which nutrients are cycled within the system.
nitrogen is the most abundant atmospheric gas,yet is a limiting factor. this presentation is a bird's eye view, of nitrogen cycle, its fixation, uptake and assimilation in plants
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
1. PLANT NUTRITION AND CROP
PRODUCTIVITY
Said H. Marzouk
RHIZOSPHERE EFFECT ON MINERAL
NUTRITION OF PLANTS WITH EMPHASIS ON
BNF, NUTRIENT SOLUBILIZATION AND
UPTAKE
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2. Rhizosphere • The zone of soil immediately
adjacent to roots that supports high
levels of microbial activity.
(Rovira and Davey, 1973)
Two major systems
1. Shoot system =
photosynthesis
2. Root system =
water and
minerals uptake
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3. Rhizosphere effects
• Rhizosphere is strongly adhering dense layer and
consists of root hairs, soil particles, and soil microbes.
• The effects of the biological, chemical, and physical
changes in the Rhizosphere soils that occur because of
root exudates and rhizodeposition is known as
Rhizosphere effects (REs)
• The root exudates acts as a signaling messenger that
initiates biological communication between the soil
microbes and plant roots
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4. Microbes in the
Rhizosphere
• Microbial community, including
endophytes, pathogens and
beneficial microbes
• Beneficial microbes are classified
into two broad groups based on
their effects:
I. Plant growth-promoting
microbes, PGPM)
II. Biological control agents (BCA)
Endophytes
• provide
metabolites that
promotes plant
growth and help in
adapt better
environment
• Protect plant
against biotic and
abiotic stress
• Alleviate metal
toxicity
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5. Plant growth-promoting rhizobacteria (PGPM)
• Group of beneficial microbes capable of colonizing the
rhizosphere and able to benefit plants by improving their
productivity and immunity.
(i) Synthesis of substances that can be assimilated directly
by plants
(ii) Mobilization of nutrients
(iii) Prevention of plant diseases
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6. Factors affecting microbes in Rhizosphere
Soil PH/ Rhizosphere PH:
• pH of the rhizosphere decreases due to root
respiration.
• Acidification of rhizosphere decrease number of
microbes in the rhizosphere
• Rhizosphere effect for bacteria and protozoa is more
in slightly alkaline soil and for that of fungi is more
in acidic soils.
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7. • Proximity of root with Soil:
• The number of rhizospheric organisms is greater
near the root and their number continuously
decreases with increase in distance from the root.
• It is because concentration of organic matter
released by root in exudates decreases with
increases in distance from the root.
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8. Temperature and light intensity:
• Low temperature and low light intensity decreases
the rate of exudate secretion from the root so that
number of rhizospheric organisms decreases.
• On the other hand number of microbes in
rhizosphere increases when temperature and light
intensity increases as multiplication rate is high.
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9. Depth of root:
• In general number of rhizosphere microorganisms
decrease with increase in depth of root, which is
mainly due to anaerobic condition.
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10. Plant Species:
• Amounts and types of exudates secretion differ
with plant species, that influence growth of
rhizosphere microbes.
• For example some plant roots releases
antimicrobial chemicals such as glycosides,
hydrocyanic acids, and several antifungal agents
that inhibit rhizospheric microbes
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11. Root exudates :
• Root exudates mostly include sugars, amino acids,
peptides, vitamins, nucleotides, organic acids, enzymes,
fungal stimulants, and also some other compounds which
help in plant water uptake, plant defense, and stimulation
(Pate et al., 2001)
• It is the main factor that influence microbial community
• Different microbial community were influenced by
different root exudates
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12. Mineral solubilization
• Mineral solubilization is ability of M.O to convert
insoluble forms of minerals to soluble form that can be
absorbed by plants
• Different microbial species have mineralization and
solubilization potential for organic and inorganic minerals
(Hilda and Fraga, 2000)
• Solubilizing activity is determined by the ability of
microbes to release metabolites such as organic acids,
which through their hydroxyl and carboxyl groups chelate
the cation bound to metals and converted to soluble forms
(Sagoe et al., 1998).
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13. Phosphorous
• Phosphorous is a major growth limiting nutrient.
• As like nitrogen, there is no large atmospheric source that
can be made biologically available
• Soil P precipitated as orthophosphate and adsorbed by Fe
and Al oxides.
• P also precipitated and adsorbed by Ca in alkaline soils
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14. Phosphate solubilization cont…
• Numerous soil micro-flora were reported to solubilize
insoluble phosphorous complexes into solution and make
it possible for its use by the plant (Tripura et al. 2005).
• Several groups of fungi and bacteria, popularly called as
phosphate-solubilizing micro-organisms (PSMs) assist
the plants in mobilization of insoluble forms of
phosphate.
• Some bacterial species have mineralization and
solubilization potential for organic and inorganic
phosphorus.
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15. • Phosphorus solubilizing activity is determined by the
ability of microbes to release metabolites such as organic
acids
• OA through their hydroxyl and carboxyl groups chelate
the cation bound to phosphate, the latter being converted
to soluble forms (Sagoe et al., 1998).
• Symbiotic relationship between PSB and plants is
synergistic in nature as bacteria provide soluble
phosphate and plants supply sugars that can be
metabolized for bacterial growth (Pérez et al., 2007)
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16. Phosphate solubilization
• A significant increase in the grain yield was observed for
rice, soybean, cowpea and also an increase in the
phosphate uptake in the potato tubers was observed
when Pseudomonas striata, Aspergillus
awamori and Bacillus polymyxa were used (Gaur and
Ostwal, 1972).
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17. Organic acids produced by PSMs that aid in P solubilization
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18. Biological nitrogen fixation
• Nitrogen is one of the most important macronutrient
• N2 gas are found 78.084% in the atmosphere as N≡N
• Biological nitrogen fixation is a specific process in which
the atmospheric nitrogen is converted to ammonia by an
enzyme called nitrogenase
• BNF is mostly accomplished by microorganisms called
diazotrophs or N2 fixers.
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19. Biological nitrogen
• Diazotrophs includes some species of bacteria,
fungi, blue green algae (Cyanobacteria), lichens
etc.
• The enzyme nitrogenase fix atmospheric nitrogen
to NH3
• Only microorganism with nitrogenase enzyme are
able to fix N2
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20. Types of Biological Nitrogen Fixers
• Biological nitrogen fixers are classified based on
fixing microorganisms.
• They are usually two types as follows:
1. Symbiotic
2. Non-symbiotic
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21. Factors affecting N2 fixation
1. Presence of nitrate or ammonium
2. Presence of certain inorganic substances Ca, Co, Mo –
influence N2 fixation along with P.
3. Availability of energy source – addn. of C source
increase N2 fixation.
4. pH : Neutral – favours Azotobacter – Acidic Beijerinkia
5. Soil moisture : Adequate is good for fixation.
6. Temperature: Mesophilic – 30°C.
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22. • There are three ways that nitrogen gets “fixed”
• Industrial N2 fixation
• Non biological N2 fixation
• biological N2 fixation
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23. • Industrial N2 fixation
• Accomplished by Haber -Bosch process
• Developed in Germany 1914 by Fritz haber & Karl bosch
• Process- N2 and H2 react with each other in presence of
• Industrial catalyst( nickel / iron)
• High temperature about 500 ͦ c High pressure – 200 atm
To form NH3
• Source of H2 - is methane (natural gas)
• Industrial production of fertilizers and explosives
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24. • Non biological N₂ fixation
• Non biological / physico chemical N2 fixation involves
the photochemical & electro chemical conversion of atm.
N₂ to soil NO2, NO3, NH3.
• It is brought about by ionizing phenomena such as
cosmic radiations, meteor trails ,lightning, thunderstorms,
volcanic eruptions etc.
• These provides high energy for breaking N≡N & also for
the formation of free N₂ with oxygen or hydrogen of atm
H₂0
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25. • combination of N₂ with o₂ forms nitrous and nitric oxides.
• Combination of N₂ with hydrogen forms NH3 Nitrous and
nitric oxides get hydrated with atm. Water vapour and
forms nitrous and nitric acids
• Rain water bring these acids and NH3 to soil surface
• There ,the acids react with metallic ions and form metallic
nitrates.
• These nitrates and NH3 enrich the surface soil
• Non biological N₂ fixation amounts to only ˂ 10% of the
natural N₂ fixation
• It is common in some tropical regions, where thunder bolt
are frequent
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27. • Biological Nitrogen Fixation
• Biological nitrogen fixation was discovered by the
German agronomist Hermann Hellriegel and Dutch
microbiologist Martinus Beijerinck.
• Biological nitrogen fixation (BNF) occurs when
atmospheric nitrogen is converted to ammonia by an
enzyme called nitrogenase
• The reaction for BNF is:
N2+16ATP+8H++8 e − → 2 NH3+H2+16ADP+16Pi
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28. 2) Theory of Burris and Wilson
Hydroxylamine is the central compound of N fixation from
which ammonia is formed through reduction.
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29. Special features of diazotrophs
• Free living –bacteria like Azotobacter, rhodopseudomonas
fix atm. N₂ & also protects nitrogenase enzyme –
sensitive to 0₂
• They produce exopolysaccharides (slime) which retains
water and prevents diffusion of 0₂ inside cell during N₂
fixation
• Azotobacter have exceedingly high rate of respiratory
metabolism thus preventing 0₂ retention inside the cell
• Blue green algae –are of 2 kinds
• One that possess heterocyst
• Other that devoid of it ( non heterocystous)
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30. • Filamentous cyanobacteria contain pale , thick walled , hollow
cells called heterocyst
• Heterocyst are the site of N₂ fixation
• They lack PSII and photosynthetic bile proteins
• Non heterocystous N₂ fixing BGA like (oscillatoria) - the
filaments are arranged clumps and N₂ fixation takes place in
internally organized cell having reduced conditions
•
• Azospirillum peplum survive in microaerophilic conditions
associated with the rhizosphere ( area surrounding the roots )
of paddy plants - fix atm. N₂ in the rhizosphere.
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31. Site and mechanism of nitrogen fixation in nodules
Site
• Bacteroids -site of N-fixation.
Mechanism
1) Theory of Virtanen
• N fixation in roots appear immediately after nodule
formation.
• young plants fix N than the old plants.
• A great part of N- converted to-L-aspartic acid and
Lglutamic acid.
• Apart from this alpha-alanine present in nodule-
produced from L-aspartic acid by decarboxylation.
• small amount of Oxime-N and nitrite-N are also
present.
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32. 2) Theory of Burris and Wilson – hydroxylamine is
the central compound of N fixation from which
ammonia is formed through reduction.
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33. Biochemistry of nitrogen fixation
• N₂ fixers utilize atm. N₂ to synthesize NH3
• In this process , N₂ is first split up into free N₂ atoms by
breaking the triple bond , with help of enzyme
nitrogenase.
• This reaction is endergonic (energy consuming), it
requires an input of nearly 160kcal energy.
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34. Free nitrogen combines with hydrogen forming NH3
This reaction is exergonic (energy releasing)
Mediated by enzyme hydrogenase and it releases nearly 13
kcal energy.
BNF requires a net input of 147 kcal energy & an
expenditure of nearly 16 mols of ATP per each molecule of
nitrogen.
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36. Nitrogenase Complex
• Two protein components:
• Nitrogenase reductase and Nitrogenase
• Nitrogenase reductase is a 60 kD homodimer
with a single 4Fe-4S cluster
• Very oxygen-sensitive
• Binds Mg ATP
• 4 ATP required per pair of electrons transferred
• Reduction of N2 to 2NH3 + H2 requires 4 pairs
of electrons, so 16 ATP are consumed per N2
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38. • Nitrogenase
• A 220 kD heterotetramer
• Each molecule of enzyme contains 2 Mo, 32 Fe, 30
equivalents of acid-labile sulfide (Fe8S 7-8clusters, etc)
• Four 4Fe-4S clusters plus two Fe, Mo, Co, an iron-
molybdenum cofactor (Fe 7 S9 Mo homocitrate)
Nitrogenase is slow - 12 e- pairs per second, i.e., only
three molecules of N2 per second
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40. Pathway of nitrogen fixation in root nodules
• Glucose-6-phosphate acts as a electron donor
• Glucose-6-phosphate is converted to phosphogluconic
acid
Glucose-6-phosphate + NADP+ + H2O 6-phosphogluconic acid + NADPH + H+
• NADPH donates electrons to ferredoxin. Protons
released and ferredoxin is reduced.
• Reduced ferredoxin acts as electron carrier.
• Donate electron to Fe-protein to reduce it. Electrons
released from ferredoxin thus oxidized
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41. • 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
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43. Genes involved in Nitrogen fixation
• Genes involved in root nodule formation - called
nodulin genes ( nod genes)
• Nodulin genes essential for infection of plant root and
nodule formation by symbiotic N₂ fixing bacteria -
divided into 2 classes
1) include genes that specify biochemical composition of
bacterial cell surface.
• such as gene determining the synthesis of
exopolysaccharides ( exo genes) • Lipopolysaccharides
(lps gene)
• Capsular polysaccharides or K antigen & β 1,2 glucans
(ndu genes)
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44. • exo & lps genes - play a role in determining host
specificity
2) consist of nodulation genes (nod or nol)
• nod genes are involved in nodulation of particular host -
called host specific nod (hsn) genes.
• Fast growing rhizobium sps - nod genes are located on
large sym plasmids
• Slow growing brady rhizobium sps – carry late nod gene
on the bacterial chromosome.
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45. Symbiotic N2 Fixers
• Fixation of free nitrogen by micro-organisms living
symbiotically with plants.
• The term ‘symbiosis’ was first introduced by a biologist
named Debary.
These can be discussed under the following three heads
1. Nodule formation in leguminous plants.
2. Nodule formation in non-leguminous plants.
3. Non nodulation
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46. Nodule formation in Leguminous plants
• More than 2500 species of the family Leguminosae
produce root nodules with Rhizobium spp.
• Examples are Pea, Soya bean, Clover, and alfalfa
• They fix nitrogen only inside the root nodules.
• The host plants provides food and shelter to the bacteria.
• The bacteria supply fixed nitrogen to the plant.
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47. Nodule formation in non-leguminous plants
• Besides leguminous plants, some other plants also found
to form root nodules.
• Actinorhizal plants have the ability to develop an
endosymbiosis with the nitrogen-fixing soil
actinomycetes Frankia.
• The establishment of the symbiotic process results in the
formation of root nodules in which Frankia provides
fixed nitrogen to the host plant in exchange for reduced
carbon.
• Actinorhizal plants are woody shrubs and trees
• Some examples include, Causuarina, Myrica gale etc.
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49. Azolla anabaena
• Is a symbiotic relationship between cyanobacteria and
floating fern Azolla
• Anabaena is a genus of filamentous cyanobacteria, or
blue-green algae
• It is known for its nitrogen fixing abilities.
• They form symbiotic relationship with certain plants,
such as the mosquito ferns
• Anabaena has filamentous structure
• The filaments are either straight or circulate or irregular
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50. • Filamentous structure consist two type of cells
• Vegetative cell and heterocyst
• heterocyst is a differentiated Cyanobacterial cell that
carries out nitrogen fixation.
• The heterocyst function as the site for nitrogen fixation
under aerobic conditions
• Vegetative cell have high oxygen affinity and it function
as a site for photosynthesis
• Bacteria provide nitrogen to the fern, and plant provide
habitat for bacteria
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51. Non symbiotic nitrogen fixers
• Non-symbiotic N2 fixers are also known as free living
nitrogen fixers.
• They inhabit both in terrestrial and aquatic conditions.
• Fixation carried out by free living micro-organisms
which are categorized into three different groups such as
Aerobic, Anaerobic and blue green algae.
1. Free living aerobic : Azotobacter
2. Free living anaerobic : Clostridium.
3. Blue green algae
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52. Mycorrhizal
• In mycorrhizal SYMBIOSIS fungus provides to the host
plant with nutrients, such as phosphate and nitrogen.
• In return, it gets photo synthetically fixed carbon from
the host.
• They form two types of mycelium, The mycelium that is
formed within the root, the intraradical mycelium (IRM)
differs morphologically and functionally from the
extraradical mycelium (ERM), the mycelium that grows
into the soil.
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53. • Mycorrhizal plants can take up nutrients from the soil via
two pathways:
• The ‘plant pathway’ that involves the direct uptake of
nutrients from the soil by the root epidermis and its root
hairs.
• The ‘mycorrhizal pathway’ that involves the uptake of
nutrients via the extraradical mycelium of the fungus.
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It has also been defined as the zone that includes the soil influenced by the root along with the root tissues
Major substance in plants next to water. 2. Constituents elements of: a. Chlorophyll b. Cytochromes c. Alkaloids d. Many vitamins 3. Plays important role in metabolism, growth, reproduction and heredity.