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Plant Parts and Their Diseases
Lesson Plan
Part I: Why
plants are important
The objectives for Part
I are:
1. To show how
certain plants are very important to us.
2. To show that
healthy plants are important to keep people healthy.
The instructor can ask
children why plants are important to people. Six areas can be discussed:
1. Food: Children can
be asked what they had for breakfast. Example: If a child says “Pop Tarts,”
explain that flour comes from grains and jam comes from fruits. Example: If a
child says “ham and eggs,” explain that these animals were fed corn, oats,
etc.
2. Air: Ask the
children where the oxygen that we breathe comes from. When leaves make their
food with sunlight, they release oxygen.
3. Building
Materials: Ask the children what pencils, desks, and houses are made of. Wood
comes from trees (plants).
4. Clothing: Ask a
child wearing a cotton shirt if s/he knows what it is made of. Ask a child
what linen sheets are made from (flax). Many dyes originally came from plants.
5. Gifts, Beauty,
Recreation: Ask the children if they give flowers or plants on Mother’s Day,
or enjoy planting flower gardens, or playing in parks or sports fields.
6. Medicines: Many
medicines come from plants. Example: Aspirin was first found in the bark of
willow trees.
Part II:
Plant Parts - their function and diseases
The objectives for Part
II are:
1. To teach the major
parts of a plant (root, stems, leaves, flowers, fruit and seeds) and their
basic functions.
2. To teach that each
part of a plant can become diseased.
3. To show that plant
pathologists are needed to keep plants healthy.
The instructor should
discuss the six major parts of a plant. Roots, stems, leaves, flowers, fruits,
and seeds.
Each plant part has
major functions:
1. Roots absorb
minerals and water, and anchor the plants. Show examples of edible roots:
carrots, radishes, turnips, or sweet potatoes. Show photographs of how roots can
become diseased and not grow well (Figure 3).
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Figure 3. Root-knot
nematode damage on carrots. (Pathogen = nematodes; nematodes are
microscopic parasitic worms that can attack plants.) Click
image for an enlarged printout view.
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2. Stems carry
nutrients and water up and down the plant, and support the leaves. Show examples
of edible stems: asparagus, celery, or rhubarb. Stems may become diseased (Figure
4).
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Figure 4. Sclerotinia pink
rot of celery. (Pathogen = fungus; fungi are usually microscopic
multicellular organisms that can be beneficial or harmful to plants.) Click
image for an enlarged printout view.
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3. Leaves make
food (energy from the sun + CO2 + H2O = sugar). Show examples of edible leaves:
lettuce, spinach, onion, garlic, or cabbage. Leaves may become diseased (Figure
5).
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Figure 5. Bacterial soft
rot of lettuce. (Pathogen = bacterium; bacteria are single-celled
microscopic organisms.) Click image
for an enlarged printout view.
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4. Flowers
provide nectar, attract insects, and produce fruits and seeds. Show examples of
edible flowers: rose hips, broccoli florets and artichokes. Flowers may become
diseased (Figure 6).
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Figure 6. Downy mildew of
broccoli. (Pathogen = fungus; fungi are microscopic multicellular
organisms that can be beneficial or harmful to plants.) Click
image for an enlarged printout view.
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5. Fruits have
the seeds inside. Show examples of edible fruits: apples, oranges, green
peppers, or cucumbers. Explain that although cucumbers, tomatoes, green peppers
and pumpkins are grown and sold as vegetables, they are actually fruits because
they are produced from flowers and contain seeds. Fruits may become diseased (Figure
7).
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Figure 7. Cucumber belly
rot. (Pathogen = fungus; fungi are microscopic multicellular organisms
that can be beneficial or harmful to plants.) Click
image for an enlarged printout view.
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6. Seeds are
produced by plants in order to make new plants for the next generation. Show
examples of edible seeds. Sunflower seeds, popcorn (avoid nuts). Seeds may
become diseased (Figure 8).
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Figure 8. Common smut of
corn. (Pathogen = fungus; fungi are microscopic multicellular organisms
that can be beneficial or harmful to plants.) Click
image for an enlarged printout view.
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Lab exercise
The lesson objectives
for the lab exercise are:
1. To become familiar
with the various parts of plants by eating samples of each.
2. To appreciate the
value of different plant parts as food.
3. To appreciate how
the world would be different if plant pathologists did not keep plants
healthy.
Ask children to line up
and receive a piece of carrot (root), celery (stem), lettuce (leaf), broccoli
(flower and stem), cucumber (fruit), and popcorn (seed). Provide Ranch dressing
and have the children return to their seats and eat each plant part. While they
are eating, the instructor can ask what plant part they are eating. Ask the
children how their lives would be different if there were no plant pathologists
to keep their food healthy.
Discussion Questions
1. Why are plants
important to people?
2. Name a root, stem,
leaf, flower, fruit, and seed that you like to eat.
3. Do plants get
diseased? Why?
4. Why is a tomato a
fruit?
5. What are plant
pathologists and what do they do?
6. What would happen if
we could not prevent plant diseases?
Answers to Discussion
Questions
1. Why are plants
important to people?
They provide air,
food, medicines, clothing, flowers, recreation, and building materials.
2. Name a root, stem,
leaf, flower, fruit, and seed that you like to eat.
Carrot, celery,
lettuce, broccoli, cucumber, and popcorn, respectively or other suggestions.
3. Do plants get
diseased? Why?
Yes, they get
diseases, just as people do, because organisms called pathogens infect them.
4. Why is a tomato a
fruit?
Fruits have seeds
inside even though they are sold as vegetables.
5. What are plant
pathologists and what do they do?
Plant pathologists are
scientists who study plant diseases. They help growers prevent and treat diseases on their plants.
6. What would happen if
we could not prevent plant diseases?
The amount and
quality of food, building materials, clothing, ornamentals, and medicines
would be reduced.
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