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PLANTS UNDER STRESS
desert
Arid zone
Salty soil
Antarctic region
What is Stress?
• A significant deviation from the conditions
optimal for life, and eliciting changes and
responses at all functional levels of the
organism.
• Two ways
Temporary stress
Permanent stress
What Happens During Stress?
How to Recognize Stress
Effects of Stress
1. Stressor-specific effect
involve a well- defined target within the
plant.
Ex. Intense radiation causes direct damage to the thylakoid
membrane
2. Non- specific effect
Stress responses within the plant is carried out
by phytohormones.
How to Recognize Stress
• Non- specific effects of stress
a. Alterations in membrane properties
(membrane potential, transport of substances)
b. Increased respiration
c. Inhibition of photosynthesis
d. Growth disturbances
e. Lower fertility
f. Premature senescence
g. Decrease of availability of energy
How to Recognize Stress
• Intracellular decrease in availability of energy.
(Due to metabolic impairment)
• Less ATP is formed.
• It can be calculated as an Adenylate Energy
Charge(AEC).
AEC = (ATP)+ 0.5(ADP)
(ATP)+(ADP)+(AMP)
• AEC < 0.6 indicates deterioration in the vitality
of a plant, and a plant under stress.
Survival of Stress
• Survival = Stress evasion, Resistance, Recovery
Natural Environmental Constraints
• Environmental stress factors
1. Abiotic factors – mainly include
climatic factors.
2. Biotic factors – Due to activity of
animals, microorganisms or human beings.
Multiple Stresses
• In nature frequently multiple stresses are
involved.
Ex. Stress arise due to combination of strong
radiation, overheating, drought in open
habitat.
Radiation Stress
• Two ways of radiation stress
1.Excessive quantities of photosynthetically
active radiation.
2.increased absorption of UV radiation.
Light Stress
• Strong light presents the leaf with more
photochemical energy than can be utilized for
photosynthesis.
• Overloading of the photosynthetic process.
• Extremely high irradiance destroys
photosynthetic pigments and thylokoid
structures is called “photodamage”
• Shade plants may be damaged breif exposure
of strong light.
Light Stress
Conostomum tetragonium exposed to the high light intensity
Photoinhibition
• Inhibition of photosynthesis caused by
excessive radiation.
• Strong light attack photosystem II
• Brake down of Protein sub units
• Photosynthetic electron transport is
interrupted.
• Reduce efficiency of photosystem II
Photoinhibition
As an protective measure,
• Excessive radiation energy is diverted to
fluorescence and heat.
• Surplus reductive capacity in chloroplast is
used by “Xanthophyll Cycle”
Xanthophyll Cycle
Thylakoid membrane
Lumen Stroma
A moss quenches high light energy with the pigment zeaxanthin.
a) Pellia endiviifolia did not
experienced a rise in de-
epoxidized Xanthophyll.
Liverworts
b) Flullania dilatata was a rise
in the concentration of de-
epoxidized xanthophylls
that can protect cell from
chlorophyll damage
a)
b)
Adaptation to Stress from Strong Light
• Positioning leaves at an angle to the incoming
light- Receive less radiation.
• Rolling up the shoots (mosses, pteridophytes)
• Dense coverings of trichomes on the upper
surface of the leaf.
• Thickened walls in the epidermis and hypodermal
tissue-act as diffusive filters (conifer needles &
cacti)
• Presence of Anthocyanin- act as darkening filters
& shields the mesophyll.
Ultraviolet Radiation
• Two types of UV radiation
UV-A (315-400nm)
UV-B (280-315nm)
• UV-A is mainly photooxidative.
• UV-B is in addition to photooxidative action
causes photolesions in biomembranes.
UV Damage
• Breaking down the disulfide bridges in protein
molecules.
• Dimerizing thymine groups of DNA- results in
defective transcription.
• Xanthophyll cycle is disrupted by inhibiting the
violaxanthine-deepoxidase
UV Damage
Can be identified by
• Changes in enzyme activity (increased
peroxidase activity, inhibition of cytochrome
oxidase).
• Poor energy status of the cell.
• Lower photosynthetic yield.
• Disturbed growth (reduced extension growth
& pollen tube elongation).
PLANT STRESS DUE
TO EXTREME
TEMPETURES
24
KINETIC ENERGY OF MOLECULES= HEAT
KINETIC
ENERGY OF
MOLECULES
HIGH ENERGY
LOW ENERGY
HEAT
COLD
25
Temperature balance on earth by,
Solar radiation
air current
Heat and Cold effect
• Metabolic activity
• Growth
• Viability
• Distribution,
of a plant.
26
Critical temperature Thresholds
• Activity limit
(5-25 0C)
• Lethal limit
– Cold
– Heat
27
28
Heat
Highest temperature on earth- 80oC
Lethal limit- 40-70oC
High temperatures arise by,
• Higher solar radiation
• Volcanic phenomena
• Hot pools
• Fires
29
Functional disturbance of heat
• Damage physiochemical state of bio
membranes and the conformations of protein
molecules.
– Disturbance in photosynthesis
– Disturbance in transport
– Disturbance in mitochondrial respiration
30
Heat Tolerance
• Evasion of strong sunlight
– Thick cutine layer
• Heat insulating bark
– Thick fibrous bark
– Rough suberized bark
– Silica in cell walls
– Peripheral cambium layer
• Dense leaf sheaths covering the basal buds
• Withdrawal to underground organs
• Transpirational cooling
31
Most effective form of heat
protection is provide by,
Heat shock proteins
32
Type of heat resistance
Three types
• Heat sensitive species
• Relatively heat resistant eukaryotes
• Heat tolerance prokaryotes
33
Cold
lowest temperature on earth= -90oC
Lethal limit= +5 - -90oC
low temperatures arise by,
• Low solar radiations
34
Functional disturbance of cold
Above the freezing point
By Decrease the speed of chemical reactions
• Uptake of water and nutrients restricted
• Less metabolic energy
• Less biosynthesis
• assimilation reduced
• Growth stops
35
The first main detectable result of
low temperature is,
cessation of cytoplasmic
streaming
36
Mostly effect on chilling sensitive
plants. It happens in stepwise
37
Primary effect:-
LIQUID CRYSTALINE BIO MEMBRANES → SOLID GELL
Initial reversible processes:-
DAMAGE TO THE FUNCTIONALITY OF ORGANS
CLOROPLAST- INHIBIT PHOTOSINTHESIS
MITOCHONDRIA- INCREASE RESPIRATION
Final irreversible processes:-
INSUFFICIENT CARBOHUDRATES
IMPAIRED ION BALANCE
IMBALANCE IN METABOLISM
ACCUMILATION OF TOXIC SUBSTANCES
INJURY AND DEATH OF CELLS
Type of chilling sensitive plants
• Partially sensitive plants
• Totally sensitive plants
38
Below the freezing point
FROST OCCUR PERIODICALLY AND
EPISODICALLY ON EARTH
by the ice formation
• Cytoplasm destroy by ice crystals
• Block the vascular bundles
• Ice nucleation active bacteria attack
39
By ice formation less water in the
plant = Desiccation condition
arise
40
It results,
• Unfrozen solution reach abnormally
high concentration
• Toxic effect
• Enzymes get inactive
• Bio membranes are overtaxed both
osmotically and by the volume reduction
41
Freezing of cells
• intercellular • Extracellular
42
Low temperature tolerance
• No thermal insulation (no heat losses)
– Dense growth surrounding the regenerative buds
– Giant rosette
• Abscission of sensitive organs
• Depression of freezing point
• Super cooling
• Trans located ice formation (extra tissue
freezing)
43
Categories of cold resistance
• Chilling sensitive plants
• Freezing sensitive plants
• Freezing tolerance plants
44
EVOLUTION OF VASCULAR PLANTS
FOR FROST
Happen in a stepwise process
45
First step:
COLD ADAPTATION OF ENZYMES AND MEMBRANES
Second step:
IMPROVING THE SUPERCOOLING CAPACITY
Survival capacity
• Younger plants are more sensitive
• Reproductive organs are more sensitive
• Underground organs are also quite sensitive
• Above ground shoot is the least sensitive part
46
Winter desiccation
Winter conditions may result in damage due to
desiccation.
This happen by,
• Frozen soil
• Snow and ice
47
Effects of winter desiccation
• Plants can not take up enough water and
nutrient
• Loss water by stomatal transpiration
• Xylem transpiration make cavities of the water
columns in the conducting vessels
• Block the passage of water through the xylem
• Chronic damages in plant tissues
48
Harmful effect of long periods beneath
ice or snow
• Low CO2 and O2 permeability of ice sheets
• Stop the gas exchange of plant
• Respiratory CO2 increase and O2 decrease with
in the plant
• Hypoxia
• Toxic substances accumulate
• Pathogenic effect
49
Oxygen Deficiency in the Soil.
Drought
Salt Stress
Oxygen Deficiency in the Soil.
Lack of sufficient oxygen in the soil.
Extensive areas of land are temporarily inundate by
flood waters of large rivers, small rivers or streams
repeatedly overflow their banks.
the plants cover of valley soils is often buried of long
period of times.
Soils are compacted and become impermeable as a result
of construction activities.
The soil atmosphere is low in Oxygen in any
case,
Anaerobic microorganisms take over .
Creating a strongly reducing milieu which Fe2+ ,Mn2+
, H2S, Sulphides ,Lactic acid ,Butyric acid are present in
toxic concentration.
Nitrogen turnover in the soil.
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
Adventitious root developed.
Older part of the root systems often develop corky
intumescences and swollen lenticels.
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 enzymes
are partially inhibited.
Fig. 6.51
Surviving Oxygen Deficiency
Many plants can germinate, roots and grow in oxygen deficient
soil because they have developed certain adaptations to meet
conditions in an toxic environment.
Functional adaptation Morphological
adaptation
Functional adaptation
increase in alcohol dehydrogenase (ADH) during
anaerobiosis.
Protein metabolism is adjusted within a few hours
after gene activation
Morphological adaptation
A hypoxic milieu consist in the development in ventilating
tissue (aerenchyma) with a continuous systems of
intercellular spaces.
The volume of intercellular system in the root parenchyma,
swamp plants – 20%-60%
well-aerated plant – <10%
Well aerated roots may even loss oxygen to the surrounding
soil, It can detoxify harmful reducing substances :
Fe2+ Fe111- oxide.
Aeration is also furthered by temperature gradients.
Plants growing on very dense and poorly aerated soils develop
a system of laterally spreading roots near the surface.
In the flooded regions submerged parts of trunks and
branches put out dense bundles of water roots.
poplar, willow, alder, ash
In mangrove plants,
In the form of lenticels-covered respiratory roots
(pneumatophores) with a large amount of aerenchyma.
Knee roots that produced above the surface of the soil and
standing water.
Drought
A period without appreciable precipitation, during with the
water content of the soil is reduced to such an extent that
plants suffer from lack of water.
Low precipitation and high evaporation.
Strong evaporation caused by dryness of the air and
high levels of radiation.
The dry region of the earth
Functional disturbance and patterns of Injury
Decrease in turgor and a slowing down of growth process
Decrease in cell volume
Most strongly inhibited enzyme is nitrate reductase.
plants that have been treated with nitrogen containing
fertilizer in drought.
Nitrogen fixation is more sensitive to drought.
Increase in concentration of the cell sap.
Progressive dehydration of the protoplasm
Protein metabolism and synthesis of amino acids are
impaired.
Supresses cell division
Slow down mitosis- S phase being affected most.
During pollen development, the meioses exhibit
chromosome anomalies- specially metaphase and anaphase.
Drought lower pollen fertility.
During drought,
Initiate stomatal closer
Under the influence of hormone synthesized in the
leaves and roots in response to drought
Changes occur in the allocation of assimilates
The ratio of shoot to roots growth is altered
Characteristic morphogenetic features develop
Reproductive processes become predominant
Senescence is accelerated
Older leaves dry out and shed
In wilt,
The reduction of cell volume
Increasing concentration of the intercellular solutes-ions
In the final phase preceding cellular disruption
The central vacuole splits up into small fragmentary
vacuoles
The thylakoids in the chloroplasts and the mitochondrial
cristae first of all swell and are later break down
The nuclear membrane becomes distended and the
polyribosome disintegrate
Drought stress in tobacco
Fig. 6.62
Survival of Drought
Drought resistance
the capacity of a plant to withstand period of dryness, and is
a complex characteristics.
xerophytes
Desiccation Avoidance
desiccation is delayed by all those mechanisms
that enable the plant to maintain a favorable tissue water
content as long as possible despite dryness of air and
soil.
uptake of water from the soil
reduced loss of water
Water uptake
extensive root system with a large active surface area is
improved further by rapid growth into deeper soil layer
the seedling of woody plants in dry regions may have
tap roots ten times as long as the shoot
grasses in such places develop a dense root system and
send their threadlike roots to depths of some meters.
Fig 6.64
Reduction of transpiration
Modulative adptation
timely closure stomata
when leaves growing under conditions of water
deficiency develop smaller but more densely distributed
stomata.
Fig 6.65
The leaves have more densely cutinized epidermal walls
Covered with thicker layer of wax.
Stomata are present only on the under side of the leaves
smaller
often hidden beneath dense hair or in depression
Boundary layer resistance is increased and the air outside the
stomata become moisture
Rolling the leaves
Salt stress
Salt stress may have be a first chemical stress
factor encountered during the evolution of life on earth.
Saline habitats
the presents of an abnormally high content of
readily soluble salt
Aquatic saline habitat: Oceans, salt lakes, saline ponds
In land: saline soil
Effect of high salt concentration on plants
The burden of high salt concentrations for plant is due to
osmotic retention of water and to specific ionic effect on
the protoplasm.
An excess of Na+ and Cl- in the protoplasm lead to
disturbance in the ionic balance
Ion specific effects on enzyme protein and
membrane.
Too little energy is produced by photophosphorylation
and phosphorylation in respiratory chain
Nitrogen elimination is impaired
Protein metabolism is disturbed
Accumulation of diamines such as putrescine
cadaverine,polyamines
Functional disturbance
Photosynthesis is impaired
Stomata closure
Effect of salt in chloroplast in particular on electron
transport and secondary process
Respiration increased or decreased – root
Enzyme system of glycolysis and the tricarboxylic acid
cycle are more sensitive than alternative metabolic
pathways.
When the NaCl content of the soil is high the uptake of
mineral nutrients NO3
- , K+ , Ca2+ is reduced.
Extreme salt stress
Inhibition of root growth
Bud opening is delayed
Shoot are stunted
Leaves are small
Cell die and necrosis appear in roots, buds, leaf margins and
shoot tips
The leaves become yellow and dry before the growing
season has ended and whole portion of the shoot dry out.
Lower level of cytokinin
Increased abscisic acid senescence
Survival of Saline habitats
plant growing in saline habitat cannot evade the
effects of salt and must therefore develop at least some
degree of resistance to it.
Salt resistance is ability of a plant either to avoid,
salt regulation
excessive amount of salt from reaching the
protoplasm
to tolerate the toxic and osmotic effect associated
with the increased ion concentration.
Regulation of the salt content
1. Salt exclusion: In some mangrove- transport barriers of the
roots prevent the salinity of the water in the conducting
system from becoming too high.
Prosopis farcta
crop plants
halophorbic species
2. Salt elimination : A plant can rid itself of excess salt ,
releasing volatile methyl halides –
 exclusion by glands
 excretion of salt at the shoot
 shedding parts heavily loaded with salt
marine phytoplankton
macro algae
3. Salt redistribution:
Na+ and Cl- can be readily translocated in the
phloem , so that the high concentration arising in actively
transpiring leaves can be diluted by throughout the plant.
4. Salt tolerance : the protoplasmic compartment of
resistance to salt stress.
Anthropogenic stress
Man made pollutants and their impact on the
phytosphere.
Due to human activities plants exposed to greater
amounts of harmful substances.
Human activities…
• Results of industrial processes.
• Traffic.
• Chemicals used in agriculture and household,
fertilizers, pesticides.
• Excessive consumption of fossil fuels-
emmission of green house gases.
• Catastrophic accidents-nuclear reactor
activities, oil spills.
• Pollutant
A contaminant of air, water or soil that has an
adverse effect on an organism.
1.Naturally occurring pollutants
2.Anthropogenic pollutants
Instead of one pollutant activity combined
activity of pollutants.
Ex: Photo oxidant complex + SO2 (g),+ heavy
metals
Naturally occurring harmful substances in higher
concentrations.
• SO2 (g),NO2 (g),H2S (g),O3 (g)
• Dust.
• Heavy metals.
Ultimate result is environmental stress.
Ecosystems
Countries
Continents
Entire globe
• High input of pollutants within a short period
of time = acute damages
• Exposure to low concentrated pollutants for a
longer period of time = Chronic damage
Pollution Injury
The extent which vital(physiological &
biochemical) functions are affected.
Visible damage depend on many
factors of the plant.
1. Plant species.
2. Growth form.
3. Age of the plant.
4. Phase of activity.
5. General vigour(physical strength & good health.
6. Climatic and edaptic condition.
7. Chemical nature.
8. Concentration of the pollutant.
9. Time and duration of the action of the pollutant.
Air born pollutants
• SO2 (g),NOx (g), PAN (peroxyacetyl
nitrate),Hydrogen
helides, NH3(g), hydrocarbons, tar
fumes, soot, dust.
Symptoms of damage
• Non specific.
• Many symptoms interact with other plant
stress factors.
• At noon stomata are fully open atmospheric
pollutant concentration is high in noon
damage is higher.
• At night plants recover from the injurious
immisions.
Early recognition of pollution damage
1. Accumulation of toxic compounds/substances in the
plant tissues.
2. Reduction of buffering capacity of tissues.
3. Erosion of epicuticular wax .
4. Decreation /incretion of certain enzyme activities.
5. Qualitative and quantitative shifts among
metabolites.
6. Appearance of stress hormones– Ex: ethylene
7. Respiration incretion/decreation
8. Photosynthetic disturbance.
9. Alteration of stomatal opening and closure.
10. Diminished allocation of photosynthetes to the root
system.
When the pollutant in immediate
vicinity..
1. Occurrence of chlorosis.
2. Leaf discoloration.
3. Tissue necrosis.
4. Death of entire plant.
•Reduce productivity and
defective fertility.
•Less growth in cambial tissues.
•Foliage become sparser.
•Water transpiration interfered.
SO2 (g) –cause most of the damage
Natural sources-volcanic emissions, S containing
ores, biological decay and forest fires.
Man-made sources-fossil fuel combustion,
smelting, manufacture of sulfuric acid.
SO2 (g) is there in the environment since the plants
beginning.-Plants have been adapted to tolerate
SO2 (g) for some extent.
Entry into plants.
1. Enter the leaf through opened stomata.
2. By over-coming the cuticular resistance.(if the
stomata are closed)
Damage by SO2 (g)
SO2 (g)
low external
concentration
Trigger a loss of turgor in
epidermal cells
Stomata open
Transpiration high
• High external
concentration
• Stomata closure
• Low transpiration
• SO2 (g) diffuse similar as CO2 (g) .
Atmospheric SO2 (g)
Dissolved in guard cell wall water SO2 (g) +H2O(l)
HSO3
-
(aq) + SO3
2-
(aq)
Chloroplast: Cytosol: Vacuole
96 : 3 : 1
Sulphur compounds
(SO2(g),H2S (g) )detoxification
01.) SO3
2-
(aq) SO4
2-
(aq)
SO3
2-
(aq) remaining will effected by the
photosynthetic sulphur metabolism
Covert to sulphur containing amino
acids.(cysteine, methionone)
Call wall peroxidases.
Harmful effects of SO2 (g)
1. SO3
2-
(aq) Level in chloroplast rise.
2. SO2(g) ,occupies binding sites in RUBP
carboxylases.
secondary process of photosynthesis inhibits.
3.The tertiary structure of the enzymes are
disturbed.
4. SO3
2-
(aq) SO4
2-
(aq)
Super oxide radicals generate, if not excluded
rapidly chlorophyll will be destroyed.
photooxidation
Mechanisms of resistance of SO2 (g)
stress
* can be passive or active processes
Passive
Non specific, not usually related
to a particular pollutant.
1. Regular development of new
leaves with short functional
life span.
Ex:
deciduous
woody plants
• Thallophytes also have
structural, chemical
characteristics reduce the
entry of SO2
Active
Stressor specific processes.
1. High buffering capacity-from
increased uptake of alkali &
alkali earth cations.
2. Binding to 2ry products of
metabolism.
3. Metabolic use of Sulphur and
detoxifying oxidative
reactions.
4. C4 syndrome.
Ever
green
trees with
needles
Ever green tree s with needles Deciduous woody plants
C4 syndrome
C4 grass
1.Miscanthus sinensis
2.Andropogon virginicus
Moderate resistant C3
1.Polygonaceae
2.Metrosideros collina in Hawaii
Some plants have the
ability to grow in the
vicinity of volcanic
vents
Species-specific sensitivity to immissions.
• Different species
• Individual varieties and ecotypes
• Different life stages
SO2 (g) Resistant plant species introduce to
polluted areas.
Highly sensitive plants to SO2 (g) Indicator
organisms to
indicate SO2 (g)
pollution.
Atmospheric oxidants and secondary
photooxidants.
• O3(g) ,NOX(g) (NO(g) ,NO2(g)),peroxy radicals.
• NO2(g) NO(g) + O.
(g)
• O.
(g) + O2 O3(g)
• NO(g) + O3(g) NO2 (g) + O2(g)
Peroxy radicals +
hydro carbon compounds
UV 300-400 nm
Peroxyacetyl nitrtes.
Peroxybutyl nitrates.
Peroxybenzyl nitrates.
Uptake by the plant
• Through opened stomata.
• NO2(g) diffuse through cuticle, much faster
than SO2(g) .
• O3 (g) dissociate to O2(g) in the outer wall of the
epidermis.
• NO(g) ,NO2 (g) NO3
-
(aq) ,NO2
-
(aq) with water
taken up actively by living cells
Events within the cell.
• NO3
-
(aq) amino acids.
* SO2 (g) inhibit the action
of Nitrite reductase.
• Additional source of nitrates-advantageous.
• Acidification of cells/leaves-disadvantageous.
Nitrite reductase enzyme
Toxicity of nitrates
O3(g)
• O3(g) O2(g) + O.
• Peroxides,
-effect on plasma membrane.
-other bio membranes.
Transfer process
impaired.
Necrosis,growth
reduction,less
yields
Heavy metal
contamination of soil,
water
Create long term problems
metals = Zn,Pb,Ni,Co,Cr,Cu
Metalloids = Mn,Cd,Se,AS
Accumulation in
organisms, circulate
in food chains.
Common heavy metal sources
1. Industrial zones.
2. Heavy vehicle traffic.
3. Sewage sludge.
4. Emissions of dust from metal processing
industries.
5. Waste water-Cd,Zn,Fe,Pb,Cu,Cr,Hg
Uptake and toxic effects
• Uptake is mainly by roots.
-can’t stop the enter of heavy metal completely.
-need to plants as micro elements.
Toxicity due to..
1. Interference with electron transport in
respiration an photosynthesis.
2. Inactivation of vital enzymes.
Possible mechanisms of resistance
• Natural heavy metal exposures, plants growing on,
a. Metal ores.
b. Serpentine soils.
c. Strongly acidic soils.
Adaptations.
1. Immobilization in cell wall.
2. Obstruct permeation across the cell membrane.
3. Formation of chelates.
4. Compartmentalization in vacuoles.
5. Active export.
6. Characteristic patterns of iso-enzymes-
element specific resistance.
7. Genetic plasticity, with several resistance
genes-resistant to several heavy metals.
*these plant can be used to re-vegetation of strongly
heavy metal contaminated area.
Ex:
Agrostis tenuis Festuca ovina Silene vulgaris
Bioindicators of pollution impact
• Bioindicators are organisms or communities of
organisms that are sensitive to pollution stress and
respond by alteration in their vital processes or by
accumulation of the pollutant.
Bioindicators
•Indicator organisms- respond to their
surroundings, depending on their specific requirements
•Test organisms- high degree of sensitivity to certain
pollutants.
•Monitor organisms- specific responses to pollutants can be
con be used for qualitative & quantitative detection of
stress situations.
Indicator organisms
Accumulation of heavy metals influenced
by ..
1. Meteorological factors
2. Edaphic factors -Influenced by the soil rather than by the
climate.
3. Habitat related factors- growth form and rooting pattern.
Heavy metal indicators= metallophytes.
Ex: Eichhornia crassipes
Reasons for forest decline
1. Ageing of the stand.
2. Episodic damage by pests.
3. Extremes of climate.
4. Inappropriate management.
5. Interruption of mineral recycling.
6. Exhaustion of soil nutrients.
7. Toxicity caused by identifiable local emitters.
forest decline
• Depend on the,
1. Tree species.
2. Growth form.
3. The site.
4. Type of the soil.
5. Geological origin.
6. Superimposition of various stress types.
Symptoms of forest decline
1. Anomalous growth.
2. Discoloration of needles and leaves.
3. Necrosis of isolated areas of needles, leaves,
branches.
4. Shedding of leaves.(thinning of crown, bareness
of the hanging branches).
5. Dieback of leader and branch tips.
6. Increasing the shallowness of the root system.
Causes of forest decline.
• Acidic effect of precipitations.
Direct acid damage
1. necrosis of margin of leaf
2. destruction of the cuticle and cuticular waxes.
3. acidification of the apoplast– affect the distribution
of phytohormornes.
4. fine root chromosome anormalities during cell
division.
5. cells damage dissolution of cell walls tissue
disruption.
Effect of atmospheric pollutants on the
ecosystems and at the global level.
1. Acid precipitations
Green house effect
• provides temperature necessary to support
the life on earth.
• Green house gases
1. CO2(g)
2. H2O(g)
3. CH4(g)
4. O3(g)
5. N2O(g)
Green house effect
References:
1. http://www.hindawi.com/journals/jb/2012/872875/
(15.10.2012)
2. http://lqma.ifas.ufl.edu/Publication/BB-02.pdf (15.10.2012)
3. http://www.hokkaido-
ies.go.jp/seisakuka/acid_rain/Acidrain-e.html (15.10.2012)
4. Larcher W., Physiological plant ecology, 3rd edition,Springer
publications,Berlin. pp 321-449.
Plants under stress

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Plants under stress

  • 3. What is Stress? • A significant deviation from the conditions optimal for life, and eliciting changes and responses at all functional levels of the organism. • Two ways Temporary stress Permanent stress
  • 5. How to Recognize Stress Effects of Stress 1. Stressor-specific effect involve a well- defined target within the plant. Ex. Intense radiation causes direct damage to the thylakoid membrane 2. Non- specific effect Stress responses within the plant is carried out by phytohormones.
  • 6. How to Recognize Stress • Non- specific effects of stress a. Alterations in membrane properties (membrane potential, transport of substances) b. Increased respiration c. Inhibition of photosynthesis d. Growth disturbances e. Lower fertility f. Premature senescence g. Decrease of availability of energy
  • 7. How to Recognize Stress • Intracellular decrease in availability of energy. (Due to metabolic impairment) • Less ATP is formed. • It can be calculated as an Adenylate Energy Charge(AEC). AEC = (ATP)+ 0.5(ADP) (ATP)+(ADP)+(AMP) • AEC < 0.6 indicates deterioration in the vitality of a plant, and a plant under stress.
  • 8. Survival of Stress • Survival = Stress evasion, Resistance, Recovery
  • 9. Natural Environmental Constraints • Environmental stress factors 1. Abiotic factors – mainly include climatic factors. 2. Biotic factors – Due to activity of animals, microorganisms or human beings.
  • 10.
  • 11. Multiple Stresses • In nature frequently multiple stresses are involved. Ex. Stress arise due to combination of strong radiation, overheating, drought in open habitat.
  • 12. Radiation Stress • Two ways of radiation stress 1.Excessive quantities of photosynthetically active radiation. 2.increased absorption of UV radiation.
  • 13. Light Stress • Strong light presents the leaf with more photochemical energy than can be utilized for photosynthesis. • Overloading of the photosynthetic process. • Extremely high irradiance destroys photosynthetic pigments and thylokoid structures is called “photodamage” • Shade plants may be damaged breif exposure of strong light.
  • 14. Light Stress Conostomum tetragonium exposed to the high light intensity
  • 15. Photoinhibition • Inhibition of photosynthesis caused by excessive radiation. • Strong light attack photosystem II • Brake down of Protein sub units • Photosynthetic electron transport is interrupted. • Reduce efficiency of photosystem II
  • 16. Photoinhibition As an protective measure, • Excessive radiation energy is diverted to fluorescence and heat. • Surplus reductive capacity in chloroplast is used by “Xanthophyll Cycle”
  • 18. A moss quenches high light energy with the pigment zeaxanthin.
  • 19. a) Pellia endiviifolia did not experienced a rise in de- epoxidized Xanthophyll. Liverworts b) Flullania dilatata was a rise in the concentration of de- epoxidized xanthophylls that can protect cell from chlorophyll damage a) b)
  • 20. Adaptation to Stress from Strong Light • Positioning leaves at an angle to the incoming light- Receive less radiation. • Rolling up the shoots (mosses, pteridophytes) • Dense coverings of trichomes on the upper surface of the leaf. • Thickened walls in the epidermis and hypodermal tissue-act as diffusive filters (conifer needles & cacti) • Presence of Anthocyanin- act as darkening filters & shields the mesophyll.
  • 21. Ultraviolet Radiation • Two types of UV radiation UV-A (315-400nm) UV-B (280-315nm) • UV-A is mainly photooxidative. • UV-B is in addition to photooxidative action causes photolesions in biomembranes.
  • 22. UV Damage • Breaking down the disulfide bridges in protein molecules. • Dimerizing thymine groups of DNA- results in defective transcription. • Xanthophyll cycle is disrupted by inhibiting the violaxanthine-deepoxidase
  • 23. UV Damage Can be identified by • Changes in enzyme activity (increased peroxidase activity, inhibition of cytochrome oxidase). • Poor energy status of the cell. • Lower photosynthetic yield. • Disturbed growth (reduced extension growth & pollen tube elongation).
  • 24. PLANT STRESS DUE TO EXTREME TEMPETURES 24
  • 25. KINETIC ENERGY OF MOLECULES= HEAT KINETIC ENERGY OF MOLECULES HIGH ENERGY LOW ENERGY HEAT COLD 25
  • 26. Temperature balance on earth by, Solar radiation air current Heat and Cold effect • Metabolic activity • Growth • Viability • Distribution, of a plant. 26
  • 27. Critical temperature Thresholds • Activity limit (5-25 0C) • Lethal limit – Cold – Heat 27
  • 28. 28
  • 29. Heat Highest temperature on earth- 80oC Lethal limit- 40-70oC High temperatures arise by, • Higher solar radiation • Volcanic phenomena • Hot pools • Fires 29
  • 30. Functional disturbance of heat • Damage physiochemical state of bio membranes and the conformations of protein molecules. – Disturbance in photosynthesis – Disturbance in transport – Disturbance in mitochondrial respiration 30
  • 31. Heat Tolerance • Evasion of strong sunlight – Thick cutine layer • Heat insulating bark – Thick fibrous bark – Rough suberized bark – Silica in cell walls – Peripheral cambium layer • Dense leaf sheaths covering the basal buds • Withdrawal to underground organs • Transpirational cooling 31
  • 32. Most effective form of heat protection is provide by, Heat shock proteins 32
  • 33. Type of heat resistance Three types • Heat sensitive species • Relatively heat resistant eukaryotes • Heat tolerance prokaryotes 33
  • 34. Cold lowest temperature on earth= -90oC Lethal limit= +5 - -90oC low temperatures arise by, • Low solar radiations 34
  • 35. Functional disturbance of cold Above the freezing point By Decrease the speed of chemical reactions • Uptake of water and nutrients restricted • Less metabolic energy • Less biosynthesis • assimilation reduced • Growth stops 35
  • 36. The first main detectable result of low temperature is, cessation of cytoplasmic streaming 36
  • 37. Mostly effect on chilling sensitive plants. It happens in stepwise 37 Primary effect:- LIQUID CRYSTALINE BIO MEMBRANES → SOLID GELL Initial reversible processes:- DAMAGE TO THE FUNCTIONALITY OF ORGANS CLOROPLAST- INHIBIT PHOTOSINTHESIS MITOCHONDRIA- INCREASE RESPIRATION Final irreversible processes:- INSUFFICIENT CARBOHUDRATES IMPAIRED ION BALANCE IMBALANCE IN METABOLISM ACCUMILATION OF TOXIC SUBSTANCES INJURY AND DEATH OF CELLS
  • 38. Type of chilling sensitive plants • Partially sensitive plants • Totally sensitive plants 38
  • 39. Below the freezing point FROST OCCUR PERIODICALLY AND EPISODICALLY ON EARTH by the ice formation • Cytoplasm destroy by ice crystals • Block the vascular bundles • Ice nucleation active bacteria attack 39
  • 40. By ice formation less water in the plant = Desiccation condition arise 40
  • 41. It results, • Unfrozen solution reach abnormally high concentration • Toxic effect • Enzymes get inactive • Bio membranes are overtaxed both osmotically and by the volume reduction 41
  • 42. Freezing of cells • intercellular • Extracellular 42
  • 43. Low temperature tolerance • No thermal insulation (no heat losses) – Dense growth surrounding the regenerative buds – Giant rosette • Abscission of sensitive organs • Depression of freezing point • Super cooling • Trans located ice formation (extra tissue freezing) 43
  • 44. Categories of cold resistance • Chilling sensitive plants • Freezing sensitive plants • Freezing tolerance plants 44
  • 45. EVOLUTION OF VASCULAR PLANTS FOR FROST Happen in a stepwise process 45 First step: COLD ADAPTATION OF ENZYMES AND MEMBRANES Second step: IMPROVING THE SUPERCOOLING CAPACITY
  • 46. Survival capacity • Younger plants are more sensitive • Reproductive organs are more sensitive • Underground organs are also quite sensitive • Above ground shoot is the least sensitive part 46
  • 47. Winter desiccation Winter conditions may result in damage due to desiccation. This happen by, • Frozen soil • Snow and ice 47
  • 48. Effects of winter desiccation • Plants can not take up enough water and nutrient • Loss water by stomatal transpiration • Xylem transpiration make cavities of the water columns in the conducting vessels • Block the passage of water through the xylem • Chronic damages in plant tissues 48
  • 49. Harmful effect of long periods beneath ice or snow • Low CO2 and O2 permeability of ice sheets • Stop the gas exchange of plant • Respiratory CO2 increase and O2 decrease with in the plant • Hypoxia • Toxic substances accumulate • Pathogenic effect 49
  • 50. Oxygen Deficiency in the Soil. Drought Salt Stress
  • 51. Oxygen Deficiency in the Soil. Lack of sufficient oxygen in the soil. Extensive areas of land are temporarily inundate by flood waters of large rivers, small rivers or streams repeatedly overflow their banks. the plants cover of valley soils is often buried of long period of times. Soils are compacted and become impermeable as a result of construction activities.
  • 52. The soil atmosphere is low in Oxygen in any case, Anaerobic microorganisms take over . Creating a strongly reducing milieu which Fe2+ ,Mn2+ , H2S, Sulphides ,Lactic acid ,Butyric acid are present in toxic concentration. Nitrogen turnover in the soil.
  • 53. 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.
  • 54. Root growth stops. Root tips entering the low Oxygen zone die off Adventitious root developed. Older part of the root systems often develop corky intumescences and swollen lenticels.
  • 55.
  • 56. 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 enzymes are partially inhibited.
  • 58. Surviving Oxygen Deficiency Many plants can germinate, roots and grow in oxygen deficient soil because they have developed certain adaptations to meet conditions in an toxic environment. Functional adaptation Morphological adaptation
  • 59. Functional adaptation increase in alcohol dehydrogenase (ADH) during anaerobiosis. Protein metabolism is adjusted within a few hours after gene activation
  • 60. Morphological adaptation A hypoxic milieu consist in the development in ventilating tissue (aerenchyma) with a continuous systems of intercellular spaces. The volume of intercellular system in the root parenchyma, swamp plants – 20%-60% well-aerated plant – <10% Well aerated roots may even loss oxygen to the surrounding soil, It can detoxify harmful reducing substances : Fe2+ Fe111- oxide. Aeration is also furthered by temperature gradients.
  • 61. Plants growing on very dense and poorly aerated soils develop a system of laterally spreading roots near the surface. In the flooded regions submerged parts of trunks and branches put out dense bundles of water roots. poplar, willow, alder, ash
  • 62. In mangrove plants, In the form of lenticels-covered respiratory roots (pneumatophores) with a large amount of aerenchyma. Knee roots that produced above the surface of the soil and standing water.
  • 63. Drought A period without appreciable precipitation, during with the water content of the soil is reduced to such an extent that plants suffer from lack of water. Low precipitation and high evaporation. Strong evaporation caused by dryness of the air and high levels of radiation.
  • 64. The dry region of the earth
  • 65. Functional disturbance and patterns of Injury Decrease in turgor and a slowing down of growth process Decrease in cell volume Most strongly inhibited enzyme is nitrate reductase. plants that have been treated with nitrogen containing fertilizer in drought. Nitrogen fixation is more sensitive to drought. Increase in concentration of the cell sap. Progressive dehydration of the protoplasm
  • 66. Protein metabolism and synthesis of amino acids are impaired. Supresses cell division Slow down mitosis- S phase being affected most. During pollen development, the meioses exhibit chromosome anomalies- specially metaphase and anaphase. Drought lower pollen fertility.
  • 67. During drought, Initiate stomatal closer Under the influence of hormone synthesized in the leaves and roots in response to drought Changes occur in the allocation of assimilates The ratio of shoot to roots growth is altered Characteristic morphogenetic features develop Reproductive processes become predominant Senescence is accelerated Older leaves dry out and shed
  • 68. In wilt, The reduction of cell volume Increasing concentration of the intercellular solutes-ions In the final phase preceding cellular disruption The central vacuole splits up into small fragmentary vacuoles The thylakoids in the chloroplasts and the mitochondrial cristae first of all swell and are later break down The nuclear membrane becomes distended and the polyribosome disintegrate Drought stress in tobacco
  • 70. Survival of Drought Drought resistance the capacity of a plant to withstand period of dryness, and is a complex characteristics. xerophytes
  • 71. Desiccation Avoidance desiccation is delayed by all those mechanisms that enable the plant to maintain a favorable tissue water content as long as possible despite dryness of air and soil. uptake of water from the soil reduced loss of water
  • 72. Water uptake extensive root system with a large active surface area is improved further by rapid growth into deeper soil layer the seedling of woody plants in dry regions may have tap roots ten times as long as the shoot grasses in such places develop a dense root system and send their threadlike roots to depths of some meters.
  • 74. Reduction of transpiration Modulative adptation timely closure stomata when leaves growing under conditions of water deficiency develop smaller but more densely distributed stomata.
  • 76. The leaves have more densely cutinized epidermal walls Covered with thicker layer of wax. Stomata are present only on the under side of the leaves smaller often hidden beneath dense hair or in depression Boundary layer resistance is increased and the air outside the stomata become moisture Rolling the leaves
  • 77. Salt stress Salt stress may have be a first chemical stress factor encountered during the evolution of life on earth. Saline habitats the presents of an abnormally high content of readily soluble salt Aquatic saline habitat: Oceans, salt lakes, saline ponds In land: saline soil
  • 78. Effect of high salt concentration on plants The burden of high salt concentrations for plant is due to osmotic retention of water and to specific ionic effect on the protoplasm. An excess of Na+ and Cl- in the protoplasm lead to disturbance in the ionic balance Ion specific effects on enzyme protein and membrane.
  • 79. Too little energy is produced by photophosphorylation and phosphorylation in respiratory chain Nitrogen elimination is impaired Protein metabolism is disturbed Accumulation of diamines such as putrescine cadaverine,polyamines
  • 80. Functional disturbance Photosynthesis is impaired Stomata closure Effect of salt in chloroplast in particular on electron transport and secondary process Respiration increased or decreased – root Enzyme system of glycolysis and the tricarboxylic acid cycle are more sensitive than alternative metabolic pathways. When the NaCl content of the soil is high the uptake of mineral nutrients NO3 - , K+ , Ca2+ is reduced.
  • 81. Extreme salt stress Inhibition of root growth Bud opening is delayed Shoot are stunted Leaves are small Cell die and necrosis appear in roots, buds, leaf margins and shoot tips The leaves become yellow and dry before the growing season has ended and whole portion of the shoot dry out. Lower level of cytokinin Increased abscisic acid senescence
  • 82. Survival of Saline habitats plant growing in saline habitat cannot evade the effects of salt and must therefore develop at least some degree of resistance to it. Salt resistance is ability of a plant either to avoid, salt regulation excessive amount of salt from reaching the protoplasm to tolerate the toxic and osmotic effect associated with the increased ion concentration.
  • 83. Regulation of the salt content 1. Salt exclusion: In some mangrove- transport barriers of the roots prevent the salinity of the water in the conducting system from becoming too high. Prosopis farcta crop plants halophorbic species 2. Salt elimination : A plant can rid itself of excess salt , releasing volatile methyl halides –  exclusion by glands  excretion of salt at the shoot  shedding parts heavily loaded with salt marine phytoplankton macro algae
  • 84. 3. Salt redistribution: Na+ and Cl- can be readily translocated in the phloem , so that the high concentration arising in actively transpiring leaves can be diluted by throughout the plant. 4. Salt tolerance : the protoplasmic compartment of resistance to salt stress.
  • 85. Anthropogenic stress Man made pollutants and their impact on the phytosphere. Due to human activities plants exposed to greater amounts of harmful substances.
  • 86. Human activities… • Results of industrial processes. • Traffic. • Chemicals used in agriculture and household, fertilizers, pesticides. • Excessive consumption of fossil fuels- emmission of green house gases. • Catastrophic accidents-nuclear reactor activities, oil spills.
  • 87. • Pollutant A contaminant of air, water or soil that has an adverse effect on an organism. 1.Naturally occurring pollutants 2.Anthropogenic pollutants Instead of one pollutant activity combined activity of pollutants. Ex: Photo oxidant complex + SO2 (g),+ heavy metals
  • 88. Naturally occurring harmful substances in higher concentrations. • SO2 (g),NO2 (g),H2S (g),O3 (g) • Dust. • Heavy metals. Ultimate result is environmental stress. Ecosystems Countries Continents Entire globe
  • 89. • High input of pollutants within a short period of time = acute damages • Exposure to low concentrated pollutants for a longer period of time = Chronic damage Pollution Injury The extent which vital(physiological & biochemical) functions are affected.
  • 90. Visible damage depend on many factors of the plant. 1. Plant species. 2. Growth form. 3. Age of the plant. 4. Phase of activity. 5. General vigour(physical strength & good health. 6. Climatic and edaptic condition. 7. Chemical nature. 8. Concentration of the pollutant. 9. Time and duration of the action of the pollutant.
  • 91. Air born pollutants • SO2 (g),NOx (g), PAN (peroxyacetyl nitrate),Hydrogen helides, NH3(g), hydrocarbons, tar fumes, soot, dust. Symptoms of damage • Non specific. • Many symptoms interact with other plant stress factors.
  • 92. • At noon stomata are fully open atmospheric pollutant concentration is high in noon damage is higher. • At night plants recover from the injurious immisions.
  • 93. Early recognition of pollution damage 1. Accumulation of toxic compounds/substances in the plant tissues. 2. Reduction of buffering capacity of tissues. 3. Erosion of epicuticular wax . 4. Decreation /incretion of certain enzyme activities. 5. Qualitative and quantitative shifts among metabolites. 6. Appearance of stress hormones– Ex: ethylene 7. Respiration incretion/decreation 8. Photosynthetic disturbance. 9. Alteration of stomatal opening and closure. 10. Diminished allocation of photosynthetes to the root system.
  • 94. When the pollutant in immediate vicinity.. 1. Occurrence of chlorosis. 2. Leaf discoloration. 3. Tissue necrosis. 4. Death of entire plant. •Reduce productivity and defective fertility. •Less growth in cambial tissues. •Foliage become sparser. •Water transpiration interfered.
  • 95. SO2 (g) –cause most of the damage Natural sources-volcanic emissions, S containing ores, biological decay and forest fires. Man-made sources-fossil fuel combustion, smelting, manufacture of sulfuric acid. SO2 (g) is there in the environment since the plants beginning.-Plants have been adapted to tolerate SO2 (g) for some extent. Entry into plants. 1. Enter the leaf through opened stomata. 2. By over-coming the cuticular resistance.(if the stomata are closed)
  • 96. Damage by SO2 (g) SO2 (g) low external concentration Trigger a loss of turgor in epidermal cells Stomata open Transpiration high • High external concentration • Stomata closure • Low transpiration
  • 97. • SO2 (g) diffuse similar as CO2 (g) . Atmospheric SO2 (g) Dissolved in guard cell wall water SO2 (g) +H2O(l) HSO3 - (aq) + SO3 2- (aq) Chloroplast: Cytosol: Vacuole 96 : 3 : 1
  • 98. Sulphur compounds (SO2(g),H2S (g) )detoxification 01.) SO3 2- (aq) SO4 2- (aq) SO3 2- (aq) remaining will effected by the photosynthetic sulphur metabolism Covert to sulphur containing amino acids.(cysteine, methionone) Call wall peroxidases.
  • 99.
  • 100. Harmful effects of SO2 (g) 1. SO3 2- (aq) Level in chloroplast rise. 2. SO2(g) ,occupies binding sites in RUBP carboxylases. secondary process of photosynthesis inhibits. 3.The tertiary structure of the enzymes are disturbed. 4. SO3 2- (aq) SO4 2- (aq) Super oxide radicals generate, if not excluded rapidly chlorophyll will be destroyed. photooxidation
  • 101. Mechanisms of resistance of SO2 (g) stress * can be passive or active processes Passive Non specific, not usually related to a particular pollutant. 1. Regular development of new leaves with short functional life span. Ex: deciduous woody plants • Thallophytes also have structural, chemical characteristics reduce the entry of SO2 Active Stressor specific processes. 1. High buffering capacity-from increased uptake of alkali & alkali earth cations. 2. Binding to 2ry products of metabolism. 3. Metabolic use of Sulphur and detoxifying oxidative reactions. 4. C4 syndrome. Ever green trees with needles
  • 102. Ever green tree s with needles Deciduous woody plants
  • 103. C4 syndrome C4 grass 1.Miscanthus sinensis 2.Andropogon virginicus Moderate resistant C3 1.Polygonaceae 2.Metrosideros collina in Hawaii Some plants have the ability to grow in the vicinity of volcanic vents
  • 104. Species-specific sensitivity to immissions. • Different species • Individual varieties and ecotypes • Different life stages SO2 (g) Resistant plant species introduce to polluted areas. Highly sensitive plants to SO2 (g) Indicator organisms to indicate SO2 (g) pollution.
  • 105. Atmospheric oxidants and secondary photooxidants. • O3(g) ,NOX(g) (NO(g) ,NO2(g)),peroxy radicals. • NO2(g) NO(g) + O. (g) • O. (g) + O2 O3(g) • NO(g) + O3(g) NO2 (g) + O2(g) Peroxy radicals + hydro carbon compounds UV 300-400 nm Peroxyacetyl nitrtes. Peroxybutyl nitrates. Peroxybenzyl nitrates.
  • 106. Uptake by the plant • Through opened stomata. • NO2(g) diffuse through cuticle, much faster than SO2(g) . • O3 (g) dissociate to O2(g) in the outer wall of the epidermis. • NO(g) ,NO2 (g) NO3 - (aq) ,NO2 - (aq) with water taken up actively by living cells
  • 107. Events within the cell. • NO3 - (aq) amino acids. * SO2 (g) inhibit the action of Nitrite reductase. • Additional source of nitrates-advantageous. • Acidification of cells/leaves-disadvantageous. Nitrite reductase enzyme Toxicity of nitrates
  • 108. O3(g) • O3(g) O2(g) + O. • Peroxides, -effect on plasma membrane. -other bio membranes. Transfer process impaired. Necrosis,growth reduction,less yields
  • 109. Heavy metal contamination of soil, water Create long term problems metals = Zn,Pb,Ni,Co,Cr,Cu Metalloids = Mn,Cd,Se,AS Accumulation in organisms, circulate in food chains.
  • 110. Common heavy metal sources 1. Industrial zones. 2. Heavy vehicle traffic. 3. Sewage sludge. 4. Emissions of dust from metal processing industries. 5. Waste water-Cd,Zn,Fe,Pb,Cu,Cr,Hg
  • 111. Uptake and toxic effects • Uptake is mainly by roots. -can’t stop the enter of heavy metal completely. -need to plants as micro elements.
  • 112. Toxicity due to.. 1. Interference with electron transport in respiration an photosynthesis. 2. Inactivation of vital enzymes.
  • 113. Possible mechanisms of resistance • Natural heavy metal exposures, plants growing on, a. Metal ores. b. Serpentine soils. c. Strongly acidic soils. Adaptations. 1. Immobilization in cell wall. 2. Obstruct permeation across the cell membrane. 3. Formation of chelates. 4. Compartmentalization in vacuoles. 5. Active export.
  • 114.
  • 115. 6. Characteristic patterns of iso-enzymes- element specific resistance. 7. Genetic plasticity, with several resistance genes-resistant to several heavy metals. *these plant can be used to re-vegetation of strongly heavy metal contaminated area. Ex: Agrostis tenuis Festuca ovina Silene vulgaris
  • 116. Bioindicators of pollution impact • Bioindicators are organisms or communities of organisms that are sensitive to pollution stress and respond by alteration in their vital processes or by accumulation of the pollutant. Bioindicators •Indicator organisms- respond to their surroundings, depending on their specific requirements •Test organisms- high degree of sensitivity to certain pollutants. •Monitor organisms- specific responses to pollutants can be con be used for qualitative & quantitative detection of stress situations.
  • 118. Accumulation of heavy metals influenced by .. 1. Meteorological factors 2. Edaphic factors -Influenced by the soil rather than by the climate. 3. Habitat related factors- growth form and rooting pattern. Heavy metal indicators= metallophytes. Ex: Eichhornia crassipes
  • 119. Reasons for forest decline 1. Ageing of the stand. 2. Episodic damage by pests. 3. Extremes of climate. 4. Inappropriate management. 5. Interruption of mineral recycling. 6. Exhaustion of soil nutrients. 7. Toxicity caused by identifiable local emitters.
  • 120. forest decline • Depend on the, 1. Tree species. 2. Growth form. 3. The site. 4. Type of the soil. 5. Geological origin. 6. Superimposition of various stress types.
  • 121. Symptoms of forest decline 1. Anomalous growth. 2. Discoloration of needles and leaves. 3. Necrosis of isolated areas of needles, leaves, branches. 4. Shedding of leaves.(thinning of crown, bareness of the hanging branches). 5. Dieback of leader and branch tips. 6. Increasing the shallowness of the root system.
  • 122.
  • 123. Causes of forest decline. • Acidic effect of precipitations. Direct acid damage 1. necrosis of margin of leaf 2. destruction of the cuticle and cuticular waxes. 3. acidification of the apoplast– affect the distribution of phytohormornes. 4. fine root chromosome anormalities during cell division. 5. cells damage dissolution of cell walls tissue disruption.
  • 124. Effect of atmospheric pollutants on the ecosystems and at the global level. 1. Acid precipitations
  • 125.
  • 126. Green house effect • provides temperature necessary to support the life on earth. • Green house gases 1. CO2(g) 2. H2O(g) 3. CH4(g) 4. O3(g) 5. N2O(g)
  • 127.
  • 129.
  • 130. References: 1. http://www.hindawi.com/journals/jb/2012/872875/ (15.10.2012) 2. http://lqma.ifas.ufl.edu/Publication/BB-02.pdf (15.10.2012) 3. http://www.hokkaido- ies.go.jp/seisakuka/acid_rain/Acidrain-e.html (15.10.2012) 4. Larcher W., Physiological plant ecology, 3rd edition,Springer publications,Berlin. pp 321-449.

Editor's Notes

  1. Atmosphere is not the only medium which gessoes pollutants effectsAtm gas– dissolve—water(hydrosphre)--- acidification of soil/acid rains/heavy metal &amp; fertilizer move into ground water.Interest should be centered on the interaction of combinations of pollutants and their inter-relationships, between different spheres of the environment.