The Earth’s atmosphere is divided into several layers. The lowest region, the troposphere, extends from the Earth’s surface up to about 10 kilometres (km) in altitude. Virtually all human activities occur in the troposphere. Mt. Everest, the tallest mountain on the planet, is only about 9 km high. The next layer, the stratosphere, continues from 10 km to about 50 km. Most commercial airline traffic occurs in the lower part of the stratosphere. For nearly a billion years, ozone molecules in the atmosphere have protected life on Earth from the effects of ultraviolet rays. It is a form of oxygen (O2). We all know that, oxygen we need to live and breathe. Normal oxygen consists of two oxygen atoms. Ozone, however, consists of three oxygen atoms and has the chemical formula O3.

1. TOPIC
1. Ozone depletion leading to increased ionizing
radiations and its implications on crop growth.
2. UV-B radiation- Effect of UV-B radiation on plant
processes and crop growth.
B.Rachana
RAD/2018-18
Ph.D 1st year
(GPBR)
CP-605 Climate Change and
Crop Growth

2. OZONE
DEPLETION

3. WHAT IS OZONE?
Ozone is a highly reactive gas
composed of three oxygen atoms.
There is only 3 molecules of ozone for every ten
million molecules of air.
WHAT IS THE OZONE LAYER?
The ozone layer is a deep layer of invisible gas
in the stratosphere, encircling the Earth, that has
large amounts of ozone in it.

4. Ozone-Oxygen Cycle
• Free radicals,
like chlorine ,
act as
catalysts to
the
decomposition
step (breaking
down ozone)
• These
catalysts
speed up the
reaction.

5. Where
is the
Ozone
layer?

6. WHAT ARE ULTRAVIOLET (UV)
RAYS?
U.V. rays are the most common and harmful rays
that come to Earth from the sun.
WHY DO WE NEED TO KNOW
WHAT THEY ARE?
They are an important effect of ozone depletion
that has a variety of problems for living
organisms associated with it.

7. WHAT IS OZONE DEPLETION?
Due to human activity, the ozone layer is getting
weaker, causing a hole to appear and
ultraviolet rays to enter into the Earth.

8. CF
C
9%
6%
5%
80%
Ozone depletion is contributed by:

9. The Dobson Unit is the most common unit for measuring ozone concentration
100 Dobson units – Least Amount of Ozone
500 Dobson units – Most Amount

10. CAUSE OF OZONE DEPLETION
• Chlorofluorocarbons (CFC) - a chemical
used to make refrigerators, home
insulation, plastic foam, and throwaway
food containers.
– Discovered in the 1930s by scientist Thomas
Midgley.
– Non-toxic, non-flammable, and non-reactive
with other chemical compounds.
– Made up of chlorine, fluoride, and carbon.

11. Destruction of ozone by chlorine
Molecular oxygen is broken down in the stratosphere by solar
radiation to yield atomic oxygen, which then combines with
molecular oxygen to produce ozone. The ozone is then
destroyed by chlorine atoms.

13.  To humans and
animals
 To
plants
 To Eco-
system
i. Blindness due to UV ray explosion
ii. Undesirable mutation (UV is a physical
mutagen)
iii. Cataracts and other eye related disease
iv. Burning skin extreme bleeding
v. If any human remaining in the surface they
would suffocate by
cancer like deadly diseases
i. UV-B generally reduce size, productivity and
quality of plants
ii. Disturbance in photosynthesis
iii. Destruction of plant cell
i. Carbon concentration will shoot and a
great decrease in
Oxygen concentration
ii. The ice in Antarctica will start to melt
iii. Total collapse in balance of ecosystem

14. SOLUTIONS THAT ADDRESS
OZONE DEPLETION
– Don’t use the air conditioner or use it less often. Open up
windows.
– Don’t open the refrigerator for too long. Get only what you
need, don’t linger.
– Refrain from using aerosol cans. You can use paper towels
to wipe off the dust.
– Fire extinguishers are essential, but to prevent using it, you
can try to prevent fires from occurring.
– Don’t use hairsprays.
– Montreal Protocol: an international agreement to
discontinue products with harmful chemicals affecting the
ozone layer and instead replace them for an ozone friendly
brand.

15. MONTREAL PROTOCOL
Agreement established to protect the
ozone layer by reducing the
production and consumption of
harmful substances in 1987. It
entered into force 1989 and if all
countries commit to its goal, the
ozone layer will be completely
regenerated by 2055

16. UV
Radiation

18. Ultraviolet
radiation
• Ultraviolet radiation (UVR) covers a small part of
electromagnetic spectrum lying between visible light and
X ray region
• UVR are invisible to the human eyes
• Natural source of UVR is sun

19. Types of
UVR
• 1. UVA (Long UV) – 400 – 315nm. {penetrates to dermis,
Responsible for development of slow natural tan}
• UVA is further divided into two wave ranges, UVA I,which
measures 340-400 nanometers , and UVA II which extends
from320- 340 nanometers
• 2. UVB (medium UV,erythemal UV) –
315 – 280nm. {Produces new pigment formation, sunburn, Vitamin D
synthesis.
Responsible for inducing skin cancer}
• 3. UVC (short UV,germicidal UV) –
280 – 100nm {Does not reach the surface of theearth}
most UVC is absorbed by the ozone layer and does not reach the
earth.

21. How do we measure UV
radiation levels?
oWe use the UV Index Scale.
oReported on a scale of 1 -11+.
oTake special care when the UV
Index is 5-6 or higher.

22. Positive effects of UVB
Triggers vitamin D – helps strengthen bones,
muscles and the body’s immune system.
Helps some animals’ vision – Some animals
(including birds, bees and reptiles) are able to
see into the near UV light to locate many ripe
fruits, flowers and seeds that stand out more
strongly from the background.
Aids some insects navigation – Many insects use
UV emissions from celestial objects as
references for navigating in flight.

23. EFFECT ON
MICROBES
• Sterilizing effect
• Both UV B and UV C may induce T=T dimer
formation in DNA strands
• Visible light and UV A influence recovery
from UV B injury
EFFECT OF UV B ON
BIOLOGICAL SYSTEM

24. EFFECT ON
MARINE
• Large sensitivity of most phytoplankton
organisms towards UV B.
• Seem to be under UV stress
• Affect growth, photosythesis, nitrogen
incorporation and enzyme activity

25. EFFECT ON
HUMAN
•UVA/B rays make it through our
atmosphere
•UVB rays cause sunburns.
•UVA rays go deeper in the skin
and cause wrinkles.
•All UV rays damage skin
increasing the risk of skin
cancer

26. •Solar UV radiation is 95% UVA
& 5% UVB.
•UVA causes tanning, aging &
skin cancer.
•UVB causes burning & skin
cancer.
•Tanning beds emit 2-3 times
more UVA than the sun.
•UV A does not produce vitamin
D.

27. EFFECT OF UV B ON
PLANTS
• Direct effect
• DNA damage
• Cyclobutane dimer formation
• Photosynthesis
• Disturbance for photosystem 1
• Thylakoid membrane disfunctioning
• Stomatal functioning altered
• Membrane functioning
• Peroxidation of unsaturated fatty acids
• Damage to membrane proteins

28. • Indirect effect
• Plant morphogenic effect
• Leaf thickness
• Leaf angle
• Plant architecture
• Plant phenology
• Senescence
• Flowering
• Reproduction
• Chemical composition of plant
• Tannin
• Lignin
• flavonoids

29. The influence of the UV-B radiation on plant process.

30. DNA & UV-B
• DNA absorbs UV-B radiation
• Changes shape in DNA
– Changes in the DNA molecule mean
that enzymes cannot “read” the DNA
code
– Results in mutated cells or the cells
die
• Cells have developed the ability to
repair DNA
– A special enzyme arrives at the
damage site
– removes the damaged section of
DNA
– replaces it with the proper
components
• This makes DNA somewhat
resilient to damage by UV-B

31. Flowering
• UV-B radiation can alter
both the time of flowering
as well as the number of
flowers in certain species.
• Differences in timing of
flowering may have
important consequences
for the availability of
pollinators.

32. • Physiological and developmental processes of plants are
affected by UVB radiation, even by the amount of UVB in
present-day sunlight.
• A number of economically important species of plants,
such as rice, depend on cyanobacteria residing on their
roots for the retention of nitrogen. Cyanobacteria are
sensitive to UV light and they would be affected by its
increase.
• Thinning of the ozone layer also interfere with the
photosynthetic process of plants.
• Many species of crops like sweet corn, soybean, barley,
oats, cow peas, carrots, cauliflower, tomato, cucumber,
peas and broccoli are highly sensitive to UV-B radiation.
As a result, food production could be reduced by 10% for
every 1% increase of UV-B radiation.

33. Can plants protect themselves against increased UV-
B?
• The reproductive parts of plants, such as pollen
and ovules are well shielded from solar UV-B
radiation.
• Only a small proportion of the UV-B radiation
striking leaf penetrates into the inner tissues.
• Increased thickness of leaves reducing the
proportion of inner tissues exposed to UV-B
radiation.
• Have repair mechanisms in plants
–includes repair systems for DNA damage