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Lesson A3–1
Understanding Sexual Reproduction
Unit A.
Horticultural Science
Problem Area 3.
Lesson 1.
Plant Propagation
Understanding Sexual Reproduction
New Mexico Content Standard:
Pathway Strand: Plant Systems
Standard: I: Apply principles of anatomy and physiology to produce and manage plants in
both a domesticated and natural environment.
Benchmark: I-C: Explain and use basic methods for reproducing and propagating plants.
Performance Standard: 2. Describe the components and functions of plant reproductive
parts. 3. Identify and practice methods of asexual/sexual propagation.
Student Learning Objectives.
achieving the following objectives:
Instruction in this lesson should result in students
1. Discuss the importance of plant propagation.
2. Explain the difference between sexual and asexual propagation.
3. Identify the major parts of a seed.
4. List the function of each major part of a seed.
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 1.
List of Resources.
The following resources may be useful in teaching this lesson:
Recommended Resources. One of the following resources should be selected to accompany the
lesson:
Schroeder, Charles B., et al. Introduction to Horticulture, Third Edition. Danville,
Illinois: Interstate Publishers, Inc., 2000.
Reiley, H. Edward and Carroll L. Shry, Jr. Introductory Horticulture, Sixth Edition.
Albany, New York: Delmar Publishers, 2002.
Other Resources. The following resources will be useful to students and teachers:
Ball, Vic. Ball RedBook, Sixteenth Edition. Batavia, Illinois: Ball Publishing, 1998.
Biondo, Ronald J. and Jasper S. Lee. Introduction to Plant and Soil Science and Technology, Second Edition. Danville, Illinois: Interstate Publishers, Inc., 2003.
Boodley, James W. The Commercial Greenhouse, Second Edition. Albany, New
York: Delmar Publishers, 1998.
Ingels, Jack E. Ornamental Horticulture: Science, Operations, and Management, Third
Edition. Albany, New York: Delmar Publishers, 2001.
Hill, Lewis. Secrets of Plant Propagation. Pownal, Vermont: Garden Way Publishing,
1985.
List of Equipment, Tools, Supplies, and Facilities
Writing surface
Overhead projector
Transparencies from attached masters
Terms.
The following terms are presented in this lesson (shown in bold italics):
Cotyledon
Cross-pollination
Diploid
Embryo
Endosperm
Epicotyl (plumule)
Fertilization
Gametes
Genes
Haploid
Hybrids
Hypocotyl
Pollination
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 2.
Radicle
Seed
Seed coat
Self-pollination
Sexual reproduction
Zygote
Interest Approach.
Use an interest approach that will prepare the students for the lesson. Teachers often develop approaches for their unique class and student situations. A possible
approach is included here.
Bring samples of various flowering plants to class. Also bring samples of several non flowering foliage
plants that are propagated asexually. Display them to students and ask them what they think the value of
the flower is to the plant? How are plants more successful at reproduction than animals? After a few minutes of discussion, move on to the lesson content.
Summary of Content and Teaching Strategies
Objective 1:
Discuss the importance of plant propagation.
Anticipated Problem: What would happen if plants did not have the ability to reproduce?
I. Plants are essential for life as we know it on earth.
A. Plants are the ecological producers of our planet. They provide food and shelter for
other organisms, produce oxygen to support animal respiration, and enrich our environment.
B. Throughout history people have relied on seeds and plant parts to grow new plants for
food and fiber.
C. In more recent times, knowledge of plant reproduction has resulted in the development
of plant hybrids that have enabled large scale agricultural production of food and fiber
plants.
Use TM: A3–1A to help illustrate the importance of plants to the human diet. Use TM: A3–1B and
TM: A3–1C to help students understand the amount of food and fiber plants that are produced worldwide to support the human population on earth today. Discuss the issue of food production and global
starvation. Be open to related topics of discussion that may arise i.e. genetic manipulation of food crop
plants.
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 3.
Objective 2:
Explain the difference between sexual and asexual propagation.
Anticipated Problem: How is sexual reproduction different from asexual reproduction and what
is the advantage of sexual reproduction?
II. Sexual reproduction occurs when the male sperm carried in the pollen unites with the female egg within a flower.
A. Most plants reproduce their own kind in nature by seeds that are the result of sexual
reproduction. The male sex cell (sperm) and the female sex cell (egg) are known as
gametes. The union of the gametes produces the seed that contains the embryo plant
and stored food.
B. Both the male sperm and female egg contribute genetic information to the new embryo
plant. The union of sperm and egg results in new combinations of genetic information.
These combinations produce new traits that add to the vigor of the offspring.
C. The offspring that result from this new combination of genes are known as hybrids. People have greatly improved agricultural crops through hundreds of years of hybridization.
D. The genes (deoxyribonucleic acid) are located in chromosomes. Normal plant cells contain a pair of chromosomes and are said to be diploid. Reproductive cells, the egg and
the sperm, contain a single chromosome and are said to be haploid.
E. Fertilization unites the single chromosome in the sperm nucleus with the single chromosome in the egg nucleus. This enables the fertilized egg or zygote to have a complete pair
of chromosomes (diploid).
F. Pollination is the transfer of the male sperm carried in the pollen to the female part of
the flower, the stigma. Plants rely on wind and water to transfer the pollen to the stigma.
In addition, plants depend on animals to help with pollination. Birds, insects, bats and
other animals are attracted to brightly colored, scented flowers. These animals transfer
pollen from the anthers of the flowers they visit to the stigmas of other flowers.
G. When the pollen of a plant pollinates a flower on the same plant, it is called self-pollination. Many plants have this ability to self pollinate, others do not. When the pollen of a
plant pollinates the flower on another plant of the same species, it is said to be cross-pollination.
H. Fertilization occurs when the nucleus of the sperm unites with the nucleus of the egg.
Plant fertilization is unique because the sperm contains two nuclei. Flowering plants
have a double fertilization. One sperm nucleus unites with the egg nuclei to produce a
zygote. The second sperm nucleus unites with the nuclei of the embryo sac that develops
into the endosperm.
Use TM: A3–1D to discuss the reproductive structures of the parts of the flower. Use TM: A3–1E to
illustrate pollination. Discuss agents of pollination. Ask what problems arise from the use of substances in
our environment that destroy the honey bee populations? Use TM: A3–1F to discuss the double fertilization that results from pollination.
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 4.
Objective 3:
Identify the major parts of a seed
Anticipated Problem: What are the major parts of a seed and where are they located within the
seed?
III. A seed is a living entity that serves as a bridge between generations of a plant. It is formed in
the pistil of the flower and develops from the ovule following fertilization. As the fertilized
egg (zygote) grows and develops, it becomes the embryo of the seed.
The zygote grows and develops to become the embryo of the seed. The embryo has the parts
(root, stem, leaf) of a complete plant. In addition, the seed contains stored food to support
the development and growth of the embryo. This food is stored in the area of the seed
known as either the endosperm or the cotyledon. The embryo root is the radicle, the stem is
the hypocotyl, and the leaf is the epicotyl (plumule). The embryo and endosperm (cotyledon
in some plant species) is surrounded by the protective seed coat.
Use TM: A3–1G of the monocot and dicot seed to identify seed structures. Use pre-soaked seeds to
examine the parts of the seed.
Objective 4:
List the function of each major part of a seed.
Anticipated Problem: What is the function of each major part of a dicot seed and a monocot
seed?
IV. Each part of a seed has a specific function to help ensure that a healthy new plant will
emerge from the seed.
A. The seed is a living entity which contains the embryo plant and everything necessary for
its growth and development. Dicot plants (soybean, pea, oak) have two cotyledons or
seed leaves in its seed. Monocot plants (corn, coconut, lilies) have one cotyledon in its
seed.
B. The radicle is the lower end of the hypocotyl that forms the first root of the plant. It is
the radicle that emerges from the seed first as germination begins.
C. The hypocotyl of the embryo plant develops into the true stem.
D. The epicotyl above the hypocotyl develops into a pair of small leaves. The tip of the
epicotyl may also be known as the plumule. The plumule is the terminal bud of the first
shoot to emerge from the seed.
E. The endosperm found in monocot plants is an area of high concentration of food which
is used as a food source for the embryo plant.
F. The cotyledons store food absorbed from the endosperm when the seed was formed. The
cotyledon provides the energy that permits the embryo to grow and emerge from the soil
so that it can begin to manufacture its own food through photosynthesis.
G. The seed coat surrounds the seed and protects it from injury and dehydration.
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 5.
Use TM: A3–1H of the developing embryo plant to discuss the function of each structural part. Make a
master chart to review with the students seed structures and their function.
Review/Summary.
Focus the review and summary of the lesson around the student
learning objectives. Review the diagram of seed structure. Discuss and review the vocabulary of
reproduction and the function of each seed structure.
Application.
Application can involve the following student activity: Students may dissect
pre-soaked seeds of corn and lima beans. A hand lens may be used to assist in locating the seed
embryo and other seed structures.
Evaluation.
Evaluation should focus on student achievement of the lesson objectives. Various techniques can be used, such as student performance on the application activities. The
self-check section at the end of each chapter in the suggested references will be helpful. A sample
written test is attached.
Answers to Sample Test:
Part One: Matching
1. h
2. e
3. c
4. a
5. b
6. f
7. i
8. d
9. g
10. j
Part Two: Completion
1.
2.
3.
4.
5.
diploid, haploid
seed coat
embryo
cotyledon
endosperm
Part Three: Short Answer
1. Sexual reproduction gives the plant species the means to change with a changing environment. Every time sexual reproduction occurs there is a recombining of genetic material. Most genetic changes are beneficial because they enable plants to adapt to a
changed environment and therefore survive.
2. Pollination occurs when the male pollen is transferred to the female part of the plant.
3. Pollen may be transferred by wind, water or animals to the ovary of the flower where the
nuclei of the sperm and egg unite to form a seed that contains the embryo plant.
Self-pollination is the pollination of a flower on the same plant. Cross-pollination is the
pollination of the flower on another plant.
4. Sexual propagation involves the reproduction of plants with the use of seeds. Asexual
propagation is the reproduction of new plants from the stems, leaves or roots of a parent
plant.
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 6.
Sample Test
Name_____________________________________
Test
Lesson A3–1: Understanding Sexual Reproduction
Part One: Matching
Instructions. Match the term with the correct response. Write the letter of the term by the definition.
a.
b.
c.
d.
sexual reproduction
gamete
self-pollination
radicle
e. fertilization
f. zygote
g. genes
h. hybrid
i. hypocotyl
j. epicotyl
_______ 1. Offspring of genetically different parents.
_______ 2. Process within flowering plants that results in a zygote and endosperm.
_______ 3. When pollen of a plant pollinates a flower on the same plant.
_______ 4. Propagation involving male and female reproductive cells.
_______ 5. A male or female reproductive cell.
_______ 6. A fertilized egg resulting from the union of nuclei of sperm and egg cells.
_______ 7. The embryo plant part that develops into the true stem.
_______ 8. The embryo root develops from this structure.
_______ 9. The traits inherited from the parent plants are found in these structures.
_______ 10. The first leaves develop from this part of the embryo.
Part Two: Completion
Instructions. Provide the word or words to complete the following statements.
1. Normal cells with a double set of chromosomes are said to be________________, while
those cells with a single set of chromosomes are said to be_______________________.
2. The_________________ provides a protective shell surrounding the embryo and endosperm.
3. The little plant inside a seed that eventually grows and develops into a mature plant is the
__________________.
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 7.
4. The _____________________are the seed leaves of an embryo plant in which food is
stored.
5. A monocot seed stores food as a future source of energy in the ____________________.
Part Three: Short Answer
Instructions. Provide information to answer the following questions.
1. Explain the advantage of sexual reproduction.
2. Explain how pollination occurs.
3. Describe how self-pollination and cross-pollination differ.
4. Describe the difference between sexual and asexual propagation.
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 8.
TM: A3–1A
THE IMPORTANCE OF PLANTS
IN THE HUMAN DIET
Food Guide Pyramid
A Guide to Daily Food Choices
Fats, Oils, & Sweets
USE SPARINGLY
Key
Fat (naturally
occurring and added)
Sugars
(added)
These symbols show fats, oils,
and added sugars in food.
Milk, Yogurt,
& Cheese
Group
2–3 SERVINGS
Meat, Poultry, Fish,
Dry Beans, Eggs,
& Nuts Group
2–3 SERVINGS
Vegetable
Group
3–5 SERVINGS
Fruit Group
2–4 SERVINGS
Bread, Cereal,
Rice, & Pasta
Group
6–11
SERVINGS
(Courtesy, USDA)
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 9.
TM: A3–1B
U.S. CROP ACRES
HARVESTED, 1993
All Other
16.1%
Soybeans
19.0%
Hay
20.3%
Corn
23.5%
Wheat
21.1
1,000 ACRES
Corn* . . . . . . . . . . . . . . . . 69,837
Wheat . . . . . . . . . . . . . . . . 62,647
Hay . . . . . . . . . . . . . . . . . . 60,398
Soybeans . . . . . . . . . . . . . . 56,447
Cotton . . . . . . . . . . . . . . . . 12,787
Sorghum* . . . . . . . . . . . . . . 9,837
Barley . . . . . . . . . . . . . . . . . 6,791
Oats. . . . . . . . . . . . . . . . . . . 3,793
Rice . . . . . . . . . . . . . . . . . . . 2,833
Sunflower . . . . . . . . . . . . . . 2,504
Peanuts . . . . . . . . . . . . . . . . 1,637
Dry Edible Beans . . . . . . . . 1,600
Sugar Beets. . . . . . . . . . . . . 1,413
Potatoes . . . . . . . . . . . . . . . 1,317
Sugar Cane . . . . . . . . . . . . . . 948
Tobacco . . . . . . . . . . . . . . . . . 747
Rye . . . . . . . . . . . . . . . . . . . . . 381
Other. . . . . . . . . . . . . . . . . 47,830
Safflower. . . . . . . . . . . . . 292
Flaxseed . . . . . . . . . . . . . 191
Canola. . . . . . . . . . . . . . . 187
Dry Edible Peas . . . . . . . 145
Lentils . . . . . . . . . . . . . . . 143
Peppermint Oil. . . . . . . . . 98
Sweet Potatoes . . . . . . . . 79
Hops . . . . . . . . . . . . . . . . . 43
Spearmint Oil . . . . . . . . . . 32
Mustard Seed . . . . . . . . . . 16
Austrian Winter Peas. . . . 10
Rapeseed . . . . . . . . . . . . . . 6
Source: USDA/National Agricultural Statistics Service
*Includes harvest for grain and silage
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 10.
TM: A3–1C
WORLD CORN EXPORTS*
China
22.5%
U.S.
59.3%
Argentina
9.9%
Other
5.6%
South Africa
2.7%
COUNTRY
MILLION METRIC TONS
PERCENT
United States . . . . . . . . . . . . . 33.00 . . . . . . . . . . . . . . . 59.3%
China. . . . . . . . . . . . . . . . . . . . 12.50 . . . . . . . . . . . . . . . 22.5%
Argentina . . . . . . . . . . . . . . . . 5.50 . . . . . . . . . . . . . . . 9.9%
Other . . . . . . . . . . . . . . . . . . . 3.13 . . . . . . . . . . . . . . . 5.6%
South Africa . . . . . . . . . . . . . . 1.50 . . . . . . . . . . . . . . . 2.7%
Source: Grain: World Markets and Trade, January 3, 1994
USDA Economic Research Service and Foreign Agricultural Service
*1993/1994 Projected
Marketing year data — October 1 to September 30
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 11.
TM: A3–1D
PARTS OF A
PERFECT FLOWER
Anther
Petal
Filament
Stamen
Stigma
Pistil
Style
Sepal
Ovary
Receptacle
Pedicel
(Courtesy, Interstate Publishers, Inc.)
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 12.
TM: A3–1E
POLLINATION
Pollen grains
(contain sperm)
Stigma
Ovule
Ovary
Egg cell
(Courtesy, Interstate Publishers, Inc.)
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 13.
TM: A3–1F
DOUBLE FERTILIZATION
Pollen
Stigma
1
Two sperm nuclei
2
Ovary
Pollen tube
Egg
3
Second nucleus
Egg nucleus
One sperm fertilizes
second nucleus to form
endosperm
One sperm
fertilizes egg
(Courtesy, Interstate Publishers, Inc.)
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 14.
TM: A3–1G
DICOT VS. MONOCOT SEEDS
Seed Coat
Endosperm
Epicotyl
Single
Cotyledon
Two
Cotyledons
Epicotyl
Embryo
Embryo
Seed Coat
Bean Seed (dicot)
Corn Seed (monocot)
(Courtesy, Interstate Publishers, Inc.)
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 15.
TM: A3–1H
PARTS OF A DEVELOPING
EMBRYO PLANT
Epicotyl
Cotyledon
Hypocotyl
Primary
Root
Secondary Root
Primary
Root
(Courtesy, Interstate Publishers, Inc.)
New Mexico Horticulture Lesson Plan Library
Unit A. Problem Area 3. Lesson 1. Page 16.