This document provides an overview of the nitrogen and phosphorus cycles. It begins with the student's name, course details, and introduction to the topic. For nitrogen, it discusses the history of discoveries in the cycle. It then defines the steps of the cycle including nitrogen fixation, assimilation, ammonification, nitrification, denitrification, and sedimentation. For both nitrogen and phosphorus, it discusses biological and non-biological processes, important molecules and enzymes involved, and the impacts of human activity on accelerating the cycles.
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Nitrogen and phosphorous cycle
1. ASSIGNMENT TOPIC:NITROGEN AND PHOSPHOROUS CYCLE
Name Hafiz M Waseem
ROLL NO. Mcf-1901171
Semester 2nd (E)
Department Zoology
Subject Ecology
Submitted to Dr.Nazish mazhar Ali
Submission date 31-04-2020
3. Discovery of nitrogen cycle
ī Wilfrath and Hellreigal first discovered the fact that legumes fix the
atmospheric nitrogen in the soil.
ī The fixed N2 is directly consumed by cereals during crop-rotation.
ī Beijerinck in 1922 first isolated the bacteria from the root nodules of
leguminous plants and named it Rhizobium leguminosarum.
Plants need
atmospheric
nitronen
4. Discovery of nitrogen cycle
ī Later a large number of organisms were reported for their N2-fixing
capacity.
ī The research workers of the Central Research Laboratory in the USA
first isolated an enzyme nitrogenase from the bacteria Closteridium
pasieurianum in the year 1960.
ī Later, in 1966 Dilworth and Schollhorn discovered the activities of
nitrogenase in N2 fixation.
5. Introduction
ī Nitrogen is abundantly present (78%) in the atmosphere.
ī But green plants can not utilize the atmospheric N2 directly.
ī Plants can take up N2 only from the soil.
ī N2 present in the soil can be ultimately tracked back to the atmosphere.
ī N2 is very important for plants, as it is a constituent of proteins, nucleic acids and a variety of
compounds.
ī Mostly plants obtain N2 from the soil as nitrates and ammonium salts.
ī As plants continuously absorb nitrate and ammonium salts, the soil gets depleted of fixed
nitrogen.
6. introduction
ī Besides this the leaching effect of rain and denitrifying action of some bacteria lower the nitrogen content of
the soil.
ī This loss is compensated by the processes of lightning and nitrogen fixation
ī N2 is supplied in the form of fertilizers to agricultural crops.
ī The crop rotation with cereals and legumes has been practiced for a long time to increase the N2 content of
the soil.
ī This is done because legumes fix the atmospheric N2 in the soil.
Plants not break
triple bond
between2 nitrogen
Bacteria
breake 3 bont
by chemical
7. Define
ī the process by which nitrogen is converted between its various chemical forms.
īThis transformation can be carried out through both
ī biological and
ī physical processes.
ī The conversion of molecular N2 of the atmosphere is accomplished by 2
methods
1. Lightning or Atmospheric N2-fixation (or) Non-biological N2 fixation
2. Biological Nitrogen Fixation
8. Forms of Nitrogen :ī a) organic nitrogen as
īammonium (NH4+),
ī nitrite (NO2-)
ī, nitrate (NO3-),
ī nitrous oxide (N2O)
ī, nitric oxide (NO) or b)
ī inorganic nitrogen as nitrogen gas (N2).
phytoplan
kton
Nitrogen
cycle in
water
9. Steps of nitrogen fixation
âĸ Nitrogen cycle consists of the following steps
âĸ 1. Nitrogen Fixation
âĸ 2. Nitrogen assimilation
âĸ 3. Ammonification
âĸ 4. Nitrification and
âĸ 5. Denitrification
âĸ 6. Sedimentation
12. Nitrogen fixation
īThe conversion of free nitrogen of atmosphere
into the biologically acceptable form or
nitrogenous compounds.
īThere are following ways to convert N2 into more
chemically reactive forms:
a) Biological Nitrogen fixation
b) Physiocochemical nitrogen fixation
c) Industrial nitrogen fixation
14. Physiocochemical or Non-biological nitrogen
fixation :âĸ In this process, atmospheric nitrogen
âĸ combines with oxygen (as ozone ) during lightning or
âĸ electrical discharges in the clouds and produces different
âĸ nitrogen oxides :
15. Non biological nitrogen fixation
ī The nitrogen oxides get dissolved in rain water and on
ī reaching earth surface they react with mineral
ī compounds to form nitrates and other nitrogenous
ī compounds :
16. Industrial nitrogen fixation
Haber-Bosch process.
īUnder great pressure, at a temperature of 600 temperature
and with the use of an iron catalyst, hydrogen and atmospheric
nitrogen can be combined to form ammonia (NH3) in the
17. Biological Nitrogen fixation
ī some symbiotic bacteria , blue-green algae and some free-living bacteria are
able to fix nitrogen as organic nitrogen.
e.g
īsymbiotic bacteria : Rhizobium symbiotic
ī blue-green algae : species of Nostoc, Anabaena , etc
ī free-living bacteria : Azotobacter, Clostridium, Derxia,
Rhodospirillium, etc
Sym
bioti
c
relat
ions
hip
18. Biological Nitrogen fixation
Nitrogen assimilation : In this process ,
Inorganic nitrogen in the form of
ī nitrates ,
īnitrites , and
īammonia
īIt is absorbed by the green plants via their
roots and then it is converted into
nitrogenous organic compounds.
īNitrates are first converted into ammonia
which combines with organic acids to form
aminoacids . Aminoacids are used in the
systhesis of
īproteins,
ī enzymes,
ī chlorophylls,
ī nucleic acids, etc.
19. Biological Nitrogen fixation
Ammonification :
ī It is the process of releasing ammonia by
certain microorganisms utilizing organic
compounds derived from the dead organic
remains of plants and animals and excreata
of animals .
īThe microorganisms especially involved are
īactinomycetes,
ī bacilli ( Bacillus ramosus , B. vulgaris, B.
mesenterilus )
20. Nitrification :
ī Nitrification is a process of enzymatic oxidation of ammonia to nitrate by
certain microorganisms in soil and ocean.
īNitrosomonas ammonia to nitrites
ī (NO2Nitrobacter oxidation of the nitrites into nitrates (NO3-).
21. 6. Sedimentation :
īSometimes , nitrates of soil are locked up in the rocks while they are
washed down to the sea or leached deeply into the earth along with
percolating water.This phenomena is known as sedimentation.
22. Nitrogenase complex
īNitrogen is a highly un reactive molecule, which generally requires red-hot Mg
for its reduction.
ī But under physiological temperature, N2 is made into its reactive form by an
enzyme catalyst, nitrogenase.
ī The research workers of Central Research Laboratory first isolated the enzyme
from the bacteria C. pasieurianum.
ī They are the bacteria inhabiting the soil; they prefer anerobic environment for
their proper growth and development.
23. Nitrogenase complex
īThe researchers prepared the extract of these bacteria and searched for the N2
reducing property of the extract.
ī The extract converts N2 into NH3.
ī The researchers also used radio active labelled N15 in its molecule. Since
then, Dilworth & Schollhorn et al (1966) have discovered that the enzyme
nitrogenase reduces not only the N2 into NH3 but also acetylene into ethylene.
ī The ethylene is measured by using gas chromatographic methods.
24. groups of inhibitors which inhibit the activity
of Nase
ī 1. Classical inhibitors: include diff kinds of substrates which compete for the
Nase against N2
ī Eg: Cyclopropane, HCN, Nitrogen azide, CO are competitive inhibitors
ī2. Regulatory inhibitors: O2 and ATP N itself inhibits the Nase axn.
25. Rol of protein in nase activity
īNase also requires some globular pro for its normal N reducing activity.
ī 2 types of proteins participates in Nase activity namely legHbs & nodulins.
ī 1. Leghaemoglobins: Heme protein- facilitates the free diffusion of O2 from the
cytoplasm â it creates anaerobic environment for the axn of Nase.
īâ1st isolated from the root nodules of legumes.
26.
27. Nodulin
īAnother globular protein found in the root nodules of plants infected with
Rhizobium.
ī It is produced before the root nodule starts to fix the N from the atmosphere.
ī Facilitates the proper utilization of NH3 released during N fixation. Induces
activation of a no of enzymes like uricase, glutamine synthetase, ribokinase
28. Aerobic nitrogen fixation
ī The aerobic mos produce carbohydrates
especially polysaccharides.
ī PSs hinder the free diffusion of O2 into cells.
ī PSs pretect the Nase against the oxidizing
property of O2.
ī Thus the PS permit the Nase activity in
aerobic micro organisms.
ī The aerobic mos also have some adaptations
for the protection
of Nase against the damaging agencies in the
cell.
29. Important adaptation
ī Enzyme protein association
ī Rapid respiratory metabolism
ī Association with rapid oxygen consumers
ī Association with acid lovers
ī Time specific Nase activity
ī Protection through colonization of bacteria
ī Special separation of the N2 fixing system
30. Anaerobic nitronen fixation
ī Anaerobic microbes actively reduce N into NH3
ī This NH3 is widely used in the metabolism of plants.
ī In general, Nase is denatured when it is exposed to the O2 present in the
atmosphere
ī But the Nase of Closteridium shows high rate of tolerance of O2.
ī So the organisms like Closteridium fix N2 even under aerobic condition.
ī Microbes ---fix N2 -----in association with the root
31. Symbiotic nitrogen fixation
ī Microbes ---fix N2 -----in association with the roots of higher plants.(
symbiotic N2 fixers).
īThey fix the N2 either under aerobic / anerobic
ī Eg: Rhizobium leguminosarum, R. japonicum, R.trifolli, etc,
ī They invade the roots of leguminous plants and nonleguminous
plants like Frankia, Casurina etc, for their growth & multiplication
ī After the establishment of symbiotic association, they start to fix the
atmosphere N in the soil.
32. Effect of field effect of nitrogen fixation
ī 1. Soil moisture:- moderate( â and â moisture of the soil reduce the rate
of N fixation in soil)
ī 2. Effect of Drought:- the increased water deficiency causes decrease in
the conc of legHb in the root nodules. (âN fixation)
ī 3. Oxygen tension:- â O2 tension in the soil causes â in the rate of N
fixation by microbes.
ī 4. Effect of the pH of the soil solution:
ī An â in the soil salinity â the rate of N fixation.
ī 5. Light intensity:- In photosynthetic microbes, light induces a high rate of
Photosynthesis resulting in high rate of N fixation.
ī During N fixation, the microbes
33.
34. Phosphorus history
Phosphorus was discovered
īby Hennig Brand at 1669 in
īGermany. Origin of name:
īfrom the Greek word
ī"phosphoros" meaning
ī"bringer of light"
īBrand kept his process
īa secret, phosphorus
īwas discovered
īindependently in 1680
īby an English chemist,
īRobert Boyle.
35. Phosphorus used
īWhite Phosphorus is used
īin some explosives,
īincluding rockets. This
īcaused an uproar because of
īsafety concerns.
īRed Phosphorus is used
īin match heads. You can
īsee the texture of a match
īhead next to the matches.
īFertilizer; Phosphorus is
īknown for being
īessential to DNA and to a
īlesser extent fertilizer
36. Importance of phasphoras
ī It is an essential nutrient for plants and animals.
ī It is a part of DNA-molecules and
īRNA-molecules, molecules that store
īenergy (ATP and ADP)
ī It is also a building block of certain
īparts of the human and animal body,
īsuch as the bones and teeth.
37. function of phosphoras
ī Ecological Function
ī Phosphorus is an essential nutrient for
īplants and animals.
ī Limiting nutrient for aquatic
īorganisms.
īForms parts of important lifesustaining
īmolecules that are very
īcommon in the biosphere.
38. Biological Function
ī The primary biological
īimportance of phosphates is as a
īcomponent of nucleotides, which
īserve as energy storage within cells
ī(ATP) or when linked together, form
īthe nucleic acids DNA and RNA..
39. Phosphorous cycle
īThe biogeochemical cycle that describes the
īmovement of phosphorus through
īthe lithosphere, hydrosphere, and biosphere.
īUnlike many other biogeochemical cycles,
īthe atmosphere does not play a significant
īrole in the movement of phosphorus, because
īphosphorus and phosphorus-based
īcompounds are usually solids at the typical
īranges of temperature and pressure found
īon Earth.
40.
41.
42. phosphorous cycle
1. Reservoir â
īerosion transfers phosphorus to
īwater and soil; sediments and
rocks
īthat accumulate on ocean floors
īreturn to the surface as a result of
īuplifting by geological processes
2. Assimilation â
īplants absorb inorganic PO4
ī(phosphate) from soils; animals
īobtain organic phosphorus.
3. Release â
īplants and animals release
īphosphorus when they
decompose;
īanimals excrete phosphorus in
their
īwaste products
43. Effect of human activity on phosphoras cycle
īWe remove large amounts of phosphate
īfrom the earth to make fertilizer.
īWe reduce phosphorous in tropical soils
īby clearing forests.
īWe add excess phosphates to aquatic
īsystems from runoff of animal wastes and
īfertilizers. (causes eutrophication)
45. Phosphoras cycle
īWhen rocks high in
īphosphorus are exposed to
īwater, the rock weathers
īout and goes into solution
ī2. Autotrophs absorb this
īphosphorus and use it in
īmany different ways,
ī3. Then the plant is eaten
īby a heterotroph and
īobtains phosphorus from
īthe plant
ī4. Then the phosphate
īleaves the body, and
īdecomposers move the
īphosphorus into the soil or
īwater then another plant
īwill absorb this
īphosphorus.
46.
47. Human Impacts on the Phosphorus Cycle
ī Like nitrogen, increased use of fertilizers increases phosphorus runoff into our
waterways
īand contributes to eutrophication.
ī Humans have greatly influenced the P cycle by mining P, converting it to fertilizer, and
īby shipping fertilizer and products around the globe.
ī Transporting P in food from farms to cities has made a major change in the global P
īcycle.
ī Waters are enriched in P from farms run off, and from effluent that is inadequately
treated
ībefore it is discharged to waters.
ī Natural eutrophication is a process by which lakes gradually age and become more
īproductive and may take thousands of years to progress.
ī Cultural or anthropogenic eutrophication, however, is water pollution caused by
īexcessive plant nutrients, which results in excessive growth in algae population