Ozone depletion and UV radiations leading to increased ionizing radiations and its implications on crop growth.

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 1 st year (GPBR) CP-605 C limate 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? Your Text Here Ozone layer… here ->

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. CFC 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 Span of Ozone Depletion

10. CAUSE OF OZONE DEPLETION C hloro f luoro c arbons (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.

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

13. 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.

14. 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 regenerate d by 2055

15. UV Radiation

16. 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

17. 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 from 320- 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 the earth} most UVC is absorbed by the ozone layer and does not reach the earth.

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

19. 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.

20. 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

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

22. 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

23. 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.

24. 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

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

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

27. 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

28. 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 .

29. 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.

30. 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