The document discusses various types of plant stress including temperature stress, radiation stress, and anthropogenic stress from air, water, and soil pollution. It provides details on how each type of stress can damage or inhibit plant functions like photosynthesis, enzyme activity, and membrane structure through processes like protein denaturation from high heat or heavy metal absorption from polluted soil. Adaptation mechanisms are also described such as heat shock proteins that help plants tolerate temperature fluctuations.

1. P L A N T
S T R E S S A N D B I O I N D I C A T O R S
Ishan Vinay
Shah
40504210007
MSc1
C006

2. C O N T E N T S
1. Temperature stress
2. Radiation stress
3. Anthropogenic stress
4. Bioindicators of stress

3. I N T R O D U C T I O N
What is stress?
Any physicochemical or environment factor capable of
producing an injurious effect in the living organism.
John (1989) defined stress as an overpowering pressure
of some adverse forces that prevent or decrease the
normal system of functioning.

4. 1 . T E M P E R AT U R E
S T R E S S
• They are divided into two types :
• 1. High temperature stress and
• 2. Low temperature stress

5. H I G H
T E M P E R AT U R E
S T R E S S
• At extremely high temperature beyond the limit of
survival life is destroyed by losing control on chemical
reactions, proteins undergo denaturation along with
physical changes detrimental to the organism.
• Temperature vary for each and every plants such
as higher plants cannot withstand temp. Above 50°C
but plants like cactus can survive at 55°C.

6. The temperature has large effects on enzyme substrate
affinities. Because the specific shape of the active site is
stabilized by temperature-sensitive interactions within
enzyme protein, which in turn influences the attraction
between enzyme and substrate.
At high temperature proteins will be denatured with the
loss in catalytic activity.
It has been observed that exposure of leaves to elevated
temperature 35-50°C in the biologically relevant range,
CO2 assimilation, O2 evolution and
photophosphorylation are generally inhibited.
PS-ii gets inactivated because PS-ii polypeptides gets
denatured and the inhibition of the oxygen evolving
complex as a result of Mn2+ ions.

7. • As we saw how temperature can affect the PS-ii system, but PS-I
components are more thermostable.
• At high temperature chlorophyll contents decreases and
leaf senescence process begins.
• Photophosphorylation is one process that is inhibited by high
temperature owing to thermal uncoupling.
• Heat stress has also been reported to cause prominent
ultrastructural changes in the nucleus, mitochondria, ER and
plastids.
• Fatty acids change from long chain unsaturated to short chain
saturated ones.

8. A D A P TAT I O N
• Several Araceae family members show
a special kind of respiration that is
cyanide-resistant and thermogenic.
• Since energy conservation is less the
tissue produces much waste heat as
the energy that is not conserved as
ATP.

9. H E AT S H O C K
P R O T E I N S
• The response to heat shock is one of the very well-
known environmental responses at the molecular level.
• Transcription and translation of small set of HSP is
initiated when seedlings are kept in temperature 5 or
more degrees above the optimal growing temperature.
• This was first discovered in Drosophila.

10. • Ubiquitin is also referred as a HSP because its
synthesis increases during heat stress
• It is a highly conserved protein composed of 76 amino
acids. It has protease activity and hence help in
removal of denatured or nonfunctional proteins.
• They are molecular chaperones.

11. L O W
T E M P E R AT U R E
S T R E S S
• It includes chilling as well as freezing stress.
• Chilling stress appears above 0°C and freezing stress
appears below 0°C
• Chilling stress affect several functions in plants
includingmembrane structure and function, changes in
nucleic and protein synthesis, water and nutrient
balances, cellular cytoskeletal structure,photosynthetic
and respiratory mechanism.

12. Pyruvate P1 diakineses and phosphofructokinase are inactivated by chilling
temperature as a result of converting them from tetramers to dimers.
K-mediated ATPase also gets affected.
It inhibits photosynthesis
Chilling sensitive plants can be acclimated or hardened to
low temperature by gradually reducing the temperature over an interval of
time.
To avoid freezing stress sometimes plants take the heat during day and
gradually dissapitate during cooling period

13. • Tolerance mechanism include processes thbat permits ice to form in
plant tissues without producing any damage.
• If ice formation is intracellular it can lead to cell death.
• When extracellular ice formation happens, it leads to dehydration of
cell and accumulation of solutes in the cytoplasm. This has the
advantage of lowering the freezing point of cytoplasm, which in
turns reduces the possibility of intracellular freezing.
• Plants that grow in clod temperature have developed
convenient strategies such as they grow slowly but their photosynthesis
rate is as same as that of plants growing in tropical climate.
• Photorespiration is kept to minimum.
• Carbohydrates reserves are stored underground organs and
allocate largeportions of photosynthates to the maintenance and
replenishment of roots and underground organs.

14. 2 . R A D I A T I O N
S T R E S S
• Depletion of ozone layer allows harmful radiation to fall on earth
surface which is absorbed by plants, and they gets affected.
• They alter growth and metabolism rate of plants.

15. • It causes the slowing of plant growth, damages the photosynthetic
pigments, lowers the carbon assimilation, altering the biomass
allocation ultimately results in a reduction of biomass and
productivity.
• Some plant develop defenses such as increased thickness of
leaves, production of more flavonoids, stimulation of the
antioxidant formation; activation of the reactive species to quench
free radicals.
• It also leads to epidermal deformation, changes in stomatal
conductance, changes in the ultrastructure of leaves, reduction in
the percentage of pollen germination, biomass reduction.
• Result of UV-B stress, initially bronzing, cupping, glazing of leaves
are observed which is followed by the development of irregular
patches and with prolonged exposure, these patches get converted
into brown spots and die.
• Broadleaf plants are more sensitive in comparison to narrow-leaf
plants.

16. • The members of the family Cucurbitaceae and Brassicaceae are more
sensitive.
• Reduction in leaf area occurs due to destruction of photosynthetic
pigments but to cope with the situation and to increase photosynthesis,
the number of leaves increases into the affected plants, which
ultimately leads to an increased number of branching in dicots and
increased number of tillers in monocots.
• Most of the energy is lost in repair mechanisms, leading to the
reduction in flowering and fruiting.
• The main target of UV-B is PS-II. It is made up of 2 proteins D1 & D2,
so when UV-B falls on the leaf it starts degradation of the proteins as
they are very sensitive towards UV-B leading to impairment of PS-II.
• Other changes produced by elevated UV-B include more trichomes on
the abaxial leaf surface, a reduction in the number and diameter of
xylem tubes, decreased stomatal frequency and distorted leaf area.

17. • UV-B exposure generally results in the decline in stomatal
apertures, plants that display the most rapid stomatal
closure in response to UV-B are often reported to be
resistant.
• Increased levels of UV-B radiations are responsible for the
increased reflectivity of the plant's surface i.e., the leaves
become more shiny and glabrous because of the
increased deposition of waxy material. It is a common type
of defense mechanism acquired by the plants to protect
them from harmful UV-B radiation.
• Excess UV-B exposure also induces the bronzing and
reddening of leaves, due to more production of
polyphenolic compounds like flavonoids.

18. 3 . A N T H R O P O G E N I C
S T R E S S
• There are many anthropogenic activities that leads
to plant stress, but we are going to see three
examples I.e.,
A. Air pollution
B. Water pollution
C. Soil pollution

19. A . A I R P O L L U T I O N
They damage the plants because the plants come in contact with harmful chemicals such as sulfur
nitrogen oxide and carbons. Plants physically showing the damage in a variety of ways, for
instance through stunted growth, necrotic lesions, and changes in colors.
 Destruction by the ozone in the lower atmosphere restricts respiration, obstructs stomata,
prevents photosynthesis and stunts plant growth.
Plants absorb pollutants from the air, making the air cleaner. With a build-up of too many
pollutants, plants may fail to grow as they should, including being unable to perform
photosynthesis. This, in turn, will mean plants will fail to have fewer yields than they should.
With air pollution affecting plants and their leaves, it means they will be unable to absorb carbon
dioxide as they should. This means more carbon dioxide will escape into the atmosphere, which
will further damage the ozone layer, and cause a build-up of more greenhouse gases.

20. Necrosi
s

21. B . W AT E R
P O L L U T I O N
• Plants require specific nutrients, which they get from
the soil, water and air. Polluted waters might kill some
of those nutrients, further denying the plant the ability
to get them.
• Water pollution will introduce toxins that are harmful
to plants. An accumulation of such toxins in the water
will poison the soils even for other crops or plants.
This will in turn negatively affect the solubility of
essential nutrients and ions, like Mg, Ca and K, which
are particularly vital for proper plant growth.
• Water pollution changes the growing conditions of
plants, including eroding necessary nutrients and
bringing in new and hazardous ones.

22. C . S O I L P O L L U T I O N
• Toxins will enter the soil and poison it, causing a chain
reaction. The result will be an alteration in the soil’s
biodiversity, reduction in the soil’s organic matter, as well
as its capacity to act as a filter.
• Soil pollution increases the salinity of the soil making it
unfit for vegetation, thus making it useless and barren.
• Land pollution through oil spills, pesticides, landfills, illegal
dumping and many other sources results in chemicals
seeping into the soil and eventually into the plants.
• Soil pollution, affects plants, meaning they will absorb the
pollutants. If we feed on such plants or crops, like
vegetables, we inadvertently end up poisoning ourselves.

23. 6 . B I O I N D I C AT O R S O F
S T R E S S
• Bioindicators include biological processes, species, or communities
and are used to assess the quality of the environment and how it
changes over time.
• Not all biological processes, species, or communities can serve as
successful bioindicators
• Bioindicator species effectively indicate the condition of the
environment because of their moderate tolerance to environmental
variability.
• Rare species (or species assemblages) with narrow tolerances are
often too sensitive to environmental change or too infrequently
encountered, to reflect the general biotic response.
• Ubiquitous species (or species assemblages) with very broad
tolerances are less sensitive to environmental changes which
otherwise disturb the rest of the community.

24. • Biological processes within an individual can act as
bioindicators.
• Cutthroat trout inhabit cold-water streams of the
western United States. Most individuals have an
upper thermal tolerance of 20°–25°C; thus, their
temperature sensitivity can be used as a bioindicator
of water temperature.
• Lead to local extinctions, causing compositional
shifts to warm water fisheries.

25. • In common usage, the terms "biomonitoring" and
"bioindication" are interchangeable, but in the scientific
community, these terms have more specific meanings.
• Bioindicators qualitatively assesses biotic responses to
environmental stress (e.g., presence of the lichen,
Lecanora conizaeoides, indicates poor air quality) while
Bio monitors quantitatively determine a response (e.g.,
reductions in lichen chlorophyll content or diversity
indicates the presence and severity of air pollution).
• There are three main functions of bioindicators:
1. To monitor the environment
2. To monitor ecological processes
3. To monitor biodiversity.

26. • Lichens and bryophytes are often used to assess
air pollution.
• The most common application of
macroinvertebrates as bioindicators, due to their
speciose nature, is at the community scale.
• macroinvertebrate communities have been
frequently used as environmental, ecological, and
biodiversity indicators. Currently, all 50 states of
the United States use aquatic macroinvertebrates
to assess the biological health of streams and
rivers.

27. C H A R A C T E R I S T I C P R O P E R T I E S
O F B I O I N D I C AT O R
1. Provide measurable response.
2. Response reflects the whole population/community/ecosystem response.
3. Respond in proportion to the degree of contamination or degradation .
4. Adequate local population density.
5. Common, including distribution within area of question.
6. Relatively stable despite moderate climatic and environmental variability .
7. Ecology and life history well understood.
8. Easy and cheap to survey .