The Effects of Over Exposure to Ultraviolet Radiation on the Growth of
Plants and Bacteria
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Chaffin, Mildred C. Hyde Park Career Acad.HS.
Students should be able to explain the deleterious effects of
ultraviolet radiation on the growth and development of plants and
bacteria. Also students should be able to describe the effect of
ozone on ultraviolet radiation.
String bean and mustard green seeds, ultraviolet lamp, glass apparatus,
potting soil, water trays, pots for the plants, glass plate, slide
projector, autoclave, fluorescent poster board and chalk,
slides, E.Coli bacteria, nutrient media, petri dishes, petri dishes with
nutrient agar, incubator, bunsen burner, test tube racks, NaCl,
cardboard box, ring stand
Two experiments were performed to demonstrate the effect of ultraviolet
radiation on plants and bacteria. Another experiment was performed to
further demonstrate how glass filters ultraviolet radiation. The glass
was used to mimic the effects of ozone on ultraviolet radiation.
1. String bean and mustard green seeds were germinated on cotton in
petri dishes for 3 days. During that time, the seeds were given a
few drops of water daily.
2. On day 4, the germinated seedlings were transferred to the pots
containing potting soil. Each seed type had two test groups and
one control group. Eight plants were used in each group.The two
test groups differed in that one was shielded by glass when
exposed to ultraviolet radiation (u.v.r.) -labeled (SE)- but the other
was not shielded when exposed to u.v.r. and it was labeled
3. From day 5 to day 10 the test groups were exposed to (u.v.r) for 2
1. Expose a fluorescent surface to u.v.r.in a dark room.
2. Expose the fluorescent surface to u.v.r. but this time place a
glass plate in front of the u.v.r. lamp.
1. Grow E.Coli cells in nutrient media for 24 hours.
2. Take out 1 mL of the E.Coli cells to use as the control group. Do
not expose this group to u.v.r..
3. Expose the remainder of the cells to ultraviolet light.
4. At 5, 20, and 60 seconds take out .1 mL of E.Coli cells
Place each group of cells in separate test tubes and label each one.
5. Dilute each group of cells to 10-6 concentration and plate out
.1 mL of cells on nutrient agar then incubate for 24 hrs.
Experiments have shown that ultraviolet radiation damages and
kills the cells of living organisms. The experiments performed
in this project alone demonstrate this. We see examples of its
deleterious effects not only in plants and bacteria but in human
beings as well. Skin cancer is an example of this. It is caused
by ultraviolet radiation being absorbed by our skin cells.There
are, however, protective mechanisms in our bodies and in our
environment that function to minimize or prevent the deleterious
effects caused by over exposure of living organisms to
ultraviolet radiation. Pigment, present in the skin of most
human beings, and ozone, present in the stratosphere, both serve
to absorb ultraviolet radiation.
Regan, James and Parrish, John The Science of Photomedicine.
Plenum Press, New York Medical School.
Biswas, Asit The Ozone Layer Plenum Press.
Giese, Arthur Living With Our Sun's Ultraviolet Rays.
Plenum Press: New York
Ellis, Carlton and Wells, Alfred The Chemical Action of