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2. Energy Metabolism of Plants Under
Oxygen Deficiency
Presentation
Plant Ecology -1
Topic

3. Presentation
Made By
Junaid Ahmed
BS Plant Sciences Quaid I Azam
University Islamabad

4. Oxygen is a non-metal element that is a gas at room
temperature. Its molecules contain two oxygen atoms.
Oxygen is vital for respiration, which is the process
that transfers energy from glucose to cells.
Oxygen is necessary for burning to occur. However,
burning will only happen when the mixture of fuel and
oxygen is hot enough.
Oxygen Cycle Elaborates how oxygen circulates in
various forms through nature
What is oxygen?
2OOO 

5. Oxygen occurs freely in the air trapped in the
earth crust as chemical compounds or dissolved
in water.
The circulation of oxygen is through the main
flow system including the air atmosphere the
biosphere, and the earth crust.

7. Function of Oxygen in energy Production
The cellular respiration use oxygen to release energy. The
energy is released in the form of ATP. The oxygen in our
body is used to break down glucose and create the fuel for
your muscles called ATP.
Aerobic Metabolism.
The aerobic metabolic system functions using the Krebs
Cycle, a complex series of chemical reactions that use
oxygen to convert nutrients (carbohydrates, fats, and protein)
to carbon dioxide and adenosine triphosphate (ATP), an
energy-rich compound.
Cellular respiration is the metabolic process through which
nutrient energy is converted into ATP (adenosine triphosphate)
and waste products. ... Foods are oxidized to release the
energy they store, and the released energy is used to
synthesize ATP

8. Cellular respiration is the metabolic process through which
nutrient energy is converted into ATP (adenosine triphosphate)
and waste products. ... Foods are oxidized to release the energy
they store, and the released energy is used to synthesize ATP

11. Anaerobic respiration:
When the plant cells are not provided with
enough oxygen to carry out aerobic respiration .
But still they need energy to stay alive.
So they use an emergency system of respiration,
that is Anaerobic respiration.

13. Fermentation :

14. How plants shift towards fermentation
During their life, plants and algae are exposed to a
range of oxygen concentrations that can vary from a
fully aerobic state (normoxia) to oxygen deficiency
(hypoxia) or the total absence of oxygen (anoxia)
1. Excessive rainfall can lead to soil waterlogging or
even to the complete submergence of plants, with
dramatic consequences for crops. In the context of
climate change, an increased frequency of flooding
has been observed worldwide
2. Under hypoxia or anoxia, a series of rapid and
profound molecular and metabolic responses are
activated to endure such stress.

15. Why fermentation required?
Fermentation is required because the mitochondrial
production of ATP is hampered in the absence of
oxygen.
Under these conditions, plants have to rely on the
small amount of ATP that can still be produced
through glycolysis.
A lack of the mitochondrial re-oxidation of NADH
puts glycolysis at risk of stopping soon after the
low oxygen conditions have been established,
unless an alternative mechanism for NADH re-
oxidation is activated, i.e., fermentation .

17. What is stress
A significant deviation from the conditions optimal
for life and eliciting changes and responses at all
functional levels of organism.

18. How to recognize stress
Alterations in membrane properties
Increased or decreased respiration
Lower fertility
Inhibition of photosynthesis
Decrease of availability of energy

19. Oxygen stress:
Oxygen deficiency in plants is a type of stress which leads
to functional and morphological disturbances.
When plants roots are immersed in stagnant water they
become oxygen deprived and develop root rot.
Hydroponic system work best when the nutrient solution
is oxygenated with an air pump as its delivered to the
plants.
Soil grown plants suffer from oxygen deficiency when
they are over wintered give the soil a chance to dry out
between watering and give your plants only the amount
of water they can absorb in a few hours.
Once a plant suffers from root rot its nearly impossible
to rescue it.

20. Low Oxygen Response In Plants
Low Oxygen Response is Due to Environmental Conditions
affecting Oxygen availability.
The shift from mitochondrial respiration to fermentation is
the hallmark of anaerobic metabolism in most organisms.
The microalga Chlamydomonas reinhardtii responses to
low oxygen seem to have evolved independently of higher
plants, posing questions on how the fermentative
metabolism is modulated.

21. Responses of roots to low O2
Complete submergence not only results in reduced O2
levels in soils and roots, but also in densely packed
shoot tissues, such as meristems, especially when the
flood water is turbid and hampers light penetration.

22. Brown Mushy Roots
Symptoms: Plants roots are brown and mushy rather
than white and firm. Leaves droop and are pale green to
yellow.
Cause: Oxygen Deficiency

23. Responses of shoots to low O2
Complete submergence not only results in reduced O2
levels in soils and roots, but also in densely packed
shoot tissues, such as meristems, especially when the
flood water is turbid and hampers light penetration.
Metabolic shifts upon low O2 in illuminated leaves and
found that low O2 had a negative effect on
photosynthesis and, furthermore, it clearly showed
signs of the typical hypoxia responses.
. Shoot elongation is a common flood response of
many wetland plants and crops, and the elongation
serves to restore contact with the atmosphere so that
internal aeration is sustained

24. Among crops, rice is well known to be exceptionally tolerant
to submergence.
Rice can germinate even in complete absence of O2 and rice
varieties possessing the Sub1A or Snorkel genes can adopt
survival strategies also at the adult stage.
Oriza sativa (Rice)

25. Rice Germination Under Low Oxygen
In Terms of tolerence to low Oxygen
Ricce is considered one of the most interesting
Species.
Unlike the majority of Higher Plants,
Rice is able to germinate under submergence
using the Starchy reserves of the seeds to fuel
the anaerobic metabolism.

26. Functional Disturbances and Patterns
of Injury
Roots are capable of respiring anaerobically,
continuous for some hours irregularities in
metabolism occur.
Partial pressure of Oxygen drops to 1-5 kPa
(Hypoxia)
Alternative respiratory pathway is activate.
The energy status of the adenylate system drops
substantially.
Root growth stops.
Root tips entering the low Oxygen zone die off

27. Adventitious root developed.
Older part of the root systems often develop corky
intumescences and swollen lenticels

28. Total and near total Oxygen deficiency (anoxia)
Respiration switches to anaerobic dissimilation
In the absence of terminal oxidation
Acetaldehyde and ethanol accumulate.
Abscisic acid, ethylene and ethylene precursors are
formed in larger amount.
Evoking in the leaves partial stomatal closure.
Epinasty and often abscission.
Cellular membrane systems brake down.
Mitochondia and microbodies disintegrate and their
enzymesare partially inhibited

30. Auxin and ROS
The plant growth regulator auxin has been well known for
regulating many growth and developmental processes such
as meristem development, cell division, cell elongation and
maintenance of polarity.
recently, auxin’s function has also been connected to plant
defense against stress.
Oxidative stress is a component of many abiotic stress
conditions such as drought,3 high temperature
stress,4 salinity5 and heavy metal stress6 and biotic stress
conditions such as herbivory7 and plant pathogen
interactions.
ROS have additional signaling roles in plant adaptation to
the stress

31. Reactive oxygen species.
Reactive oxygen species are chemically reactive chemical
species containing oxygen.e.g peroxides superoxide,
singlet oxygen species.
During time of environmental stress its level increases
dramatically.
This may result in significant damage to cell structure.
This is known as oxidative stress.

32. Singlet oxygen
Singlet oxygen which is produced as a by-
product of photosynthesis in plants.
Under high light , highly reactive singlet
oxygen can be produced via triple chlorophyll

33. General view on photosynthesis:
Photosynthesis
Light
Independent
Reaction
Light
Dependent
Reaction

34. http://www.quora.com

35. https://en.m.wikipedia.org

36. Damaging effects in plants
The damage caused caused by singlet oxygen is
that it reduced the photosynthetic efficiency of
photosynthesis.
the increased production of singlet oxygen result
in cell death.
Various substances such as carotenoids
,tocopherols and plastoquinone contained in
chproplast quench singlet oxygen and protect
against its toxic effects.

37. Oxygen deficiency in plants
Oxygen deficiency in plants, brought about by
waterlogging of the root system is a very common
event in nature.
Under oxygen deficiency, glycolysis and
fermentation can exceed the aerobic metabolic rate
and become the only pathway for energy
production.

38. Flooding a main cause of oxygen
DEFICIENCY
Cytoplasmic acidosis as a determinant of
flooding intolerance in plants.
Cytoplasmic acidosis is cause of meristematic
death in hypoxic root tips of maize and pea
seedlings.
Usually leakage of acid from vacuole is
responsible for cytoplasmic acidosis.

39. Epinasty
An abiotic, non
infectious disorder
called epinasty, the
downward growth of
leave.
It is caused by
production of
ethylene.
Ethylene precursor,1-
aminocyclopropane-1-
carboxylic acid.
http://www.gardenanswers.com

40. low oxygen stress as a sensor
Low oxygen stress impairs diverse plant cellular
functions, including those in the
cytosol,nucleus,mitochondria,and endoplasmic
reticulum(ER).
Actually molecular oxygen is among the most
utilized molecules in eukaryotic cellular metabolism
with more than 350 oxygen dependent reactions.
Thus , decreasing oxygen levels might be indirectly
sensed due to an impairment of various metabolic
pathways when cellular oxygen concentration
changes.

41. Germination under Hypoxic Condition
Dry Cereal seeds contain carbohydrates mainly starch to
germinate they require catabolising enzyme α- and β- amylase ,
amylopectin – debranching enzyme α- glucosidases.
Neither wheat nor barley seeds are able to germinate under
anaerobic conditions….But Rice Can….
It depends upon the activation of enzyme α- and β- amylase.
If starch catabolising enzyme is available than degradation
products become available for further metabolism
predominantly as Glucose -6-P and Fructose -6-P

42. Metabolic Events affected by Oxygen
Deficiency
Oxygen deficiency in plants, brought about by
waterlogging of the root system is a very
common event in nature.
Its consequences vary from the increase in
biomass of the shoot in relation to the root to the
loss of plants, due to seasonal flooding.
The relative reduction in root biomass and the
shift in allocation of metabolites to the shoot
during flooding

43. are probably the result of a metabolic adaptation
aimed at diminishing the demand for oxygen by the
root system

44. Reduction in Photosynthetic Activity
consequence of waterlogging and can be
attributed to several factors
lower water potential and stomatal conductance;
lower activities of photosynthetic enzymes;
impaired transport of photoassimilates due to
lower sink activity; and lower chlorophyll content.
Under oxygen deficiency, glycolysis and
fermentation can exceed the aerobic metabolic
rate and become the only pathway for energy
production.

45. Due to oxygen deficiency the mitochondrial
respiration stops as a result generation of ATP falls
from 36 to 2 moles per mole of Glucose metabolised
Although the coupling of glycolysis with
fermentation allows only limited synthesis of ATP, by
substrate level phosphorylation, it regenerates
NAD+ and removes excess protons.

46. Carbohydrate Regulation and Energy
Metabolism
The supply of carbohydrates and the regulation of
carbohydrate and energy metabolism are
important for enduring hypoxic stress.
Phloem transport is inhibited by hypoxia such that
the supply of carbohydrates to the roots
diminishes.
The roots of many plants accumulate sugars,
amino acids and reserves, such as starch and
fructans, when subjected to oxygen deficiency

47. Ozone layer affecting the Plants
Ozone affects sensitive vegetation and ecosystems,
including forests, parks, wildlife refuges and wilderness
areas. Ozone can especially cause damage during the
growing season.
Plant species that are sensitive to the effects of ozone on
their growth include trees found in many areas of the U.S.,
such as:black cherry
black cherry
quaking aspen
tulip poplar
white pine
ponderosa pine
red alder.

48. ozone exposure do to sensitive plants
When sufficient ozone enters the leaves of a sensitive plant, it
can:
Reduce photosynthesis, which is the process that plants use to
convert sunlight to energy to live and grow.
Slow the plant's growth.
Increase sensitive plants'
risk of:
diseasetulip poplar
damage from insects
effects of other pollutants
harm from severe weather.

49. Burning
If the temperature is high enough, many substances will burn in
oxygen.
When a substance burns, it reacts with oxygen: this happens in
wood fires and also in car engines, which burn petrol. The chemical
reaction transfers energy in order to make the engine work.
The scientific word for burning is combustion.

50. Ozone affects sensitive vegetation and ecosystems, including
forests, Ground-level ozone is one of the most widespread air
pollutants. Naturally-occurring ozone in the upper
atmosphere forms a layer that absorbs the sun's harmful
ultraviolet rays and protects all life on earth. But, ground-
level ozone can harm plants as well as human health.
Uper ozone layer protects the life from damaging by
absorbing harmful radiation.
Ozone

51. Oxygen used in Medicine
Medical oxygen is used to: provide a basis for virtually all
modern anaesthetic techniques. restore
tissue oxygen tension by improving oxygen availability in a
wide range of conditions such as COPD, cyanosis, shock,
severe hemorrhage, carbon monoxide poisoning, major
trauma, cardiac/respiratory arrest. Aid.
Doctors regulate the amount of oxygen in these areas as
excessive amounts of it can damage newborns, though it is
still a necessary element in these scenarios. Oxygen also
finds use in other medical areas: doctors enrich gaseous
anaesthetics with it to ensure a patient survives, for
instance.

52. Oxygen as an Ecological Indicator
study the oxygen content of a lake as a means of determining
how healthy it is, or is not. In some cases, such as algal
blooms where fertilizer run-off reaches a body of water, the
amount of oxygen in said body can be too high, and it ends
up harming the ecosystem, in some cases killing fish.
However, a certain level of it is necessary for life to grow in
water, as many species require it for life, and, in turn, other
species rely on them.

53. Industrial Uses of Oxygen
During the forging process, workers blow highly pressurized
oxygen to increase the volatile nature, and thus removal, of
undesirable compounds in steel.
It also finds use in welding, where it can increase the
temperature of a flame, allowing it to melt and weld
substances that have a higher resistance to heat.
Similarly, oxygen-rich air finds use in the creation of
acetylene and methanol, among others.

54. Some plant tissues tolerate anaerobic
conditions
Some plants can tolerate exposure to strictly anaerobic
conditions for an extended period ie weeks or months.
These include the rhizomes (underground horizontal stems)
of schoenoplectus lacustris,scripus maritimus(salt marsh
bulrush) and typha angustifolia (narrow leaved cattail)
which can survive for several months and expand their
leaves in an aerobic atmosphere.
The embryo and coleoptile of rice and echinochloa crus –
galli var.oryzicola (rice grass) can also survive weeks of
anoxia

55. Rhizome
In nature rhizomes overwinter in anaerobic mud at
the edges of lakes.
In spring once the leaves have expanded above the
mud or water surface ,o2 diffuses down through
arenchyma into the rhizome.
Metabolism then switches from anaerobic to
(fermentative )to an aerobic mode ,and roots begin to
grow using the available oxygen

56. Coleoptile
During germination of paddy (wetland ) rice and
of rice grass ,the coleoptile breaks the water
surface and becomes a diffusion pathway (a
snorkel) for O2 to the rest of the plant .
Even though rice is a wetland specie its roots are
intolerant of anoxia as those of maize .

57. Strategies to tolerate choronic anoxia
The ability of organs of wetland plants to tolerate
chronic anoxia may depend on strategies similar those
just described ,but they are clearly employed to
greater effect.
Critical features appear to be
•Control of cytoplasmic pH
•Continued generation of ATP by glycolysis and
fermentation
•And sufficient storage of fuel for anaerobic respiration
over extended periods