Understanding Sexual Reproduction · 2019-08-21 · Objective 2: Explain the difference between...

Lesson A3–1

Understanding Sexual Reproduction

Unit A. Horticultural Science

Problem Area 3. Plant Propagation

Lesson 1. 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. Instruction in this lesson should result in students

achieving the following objectives:

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. .

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 Tech-

nology, 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



Radicle

Seed

Seed coat

Self-pollination

Sexual reproduction

Zygote

Interest Approach. Use an interest approach that will prepare the students for the les-

son. 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 min-

utes 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 environ-

ment.

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 world-

wide 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.



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 fe-

male 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. Peo-

ple have greatly improved agricultural crops through hundreds of years of hybridization.

D. The genes (deoxyribonucleic acid) are located in chromosomes. Normal plant cells con-

tain 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 chromo-

some 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-pollina-

tion. 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-pol-

lination.

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 fertiliza-

tion that results from pollination.



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.



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. Vari-

ous 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. diploid, haploid

2. seed coat

3. embryo

4. cotyledon

5. endosperm

Part Three: Short Answer

1. Sexual reproduction gives the plant species the means to change with a changing envi-

ronment. Every time sexual reproduction occurs there is a recombining of genetic mate-

rial. 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.



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 defini-tion.

a. sexual reproduction e. fertilization h. hybrid

b. gamete f. zygote i. hypocotyl

c. self-pollination g. genes j. epicotyl

d. radicle

_______ 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 endo-

sperm.

3. The little plant inside a seed that eventually grows and develops into a mature plant is the

__________________.



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.



TM: A3–1A

THE IMPORTANCE OF PLANTS

IN THE HUMAN DIET



Key

Fat (naturally

occurring and added)

Sugars

(added)

These symbols show fats, oils,

and added sugars in food.

Meat, Poultry, Fish,

Dry Beans, Eggs,

& Nuts Group

2–3 SERVINGS

Fruit Group

2–4 SERVINGS

Bread, Cereal,

Rice, & Pasta

Group

6–11

SERVINGS

Fats, Oils, & Sweets

USE SPARINGLY

Milk, Yogurt,

& Cheese

Group

2–3 SERVINGS

Vegetable

Group

3–5 SERVINGS

Food Guide PyramidA Guide to Daily Food Choices

(Courtesy, USDA)

TM: A3–1B

U.S. CROP ACRES

HARVESTED, 1993



Corn

23.5%

Wheat

21.1Hay

20.3%

Soybeans

19.0%

All Other

16.1%

1,000 ACRESCorn* . . . . . . . . . . . . . . . . 69,837Wheat . . . . . . . . . . . . . . . . 62,647Hay . . . . . . . . . . . . . . . . . . 60,398Soybeans . . . . . . . . . . . . . . 56,447Cotton. . . . . . . . . . . . . . . . 12,787Sorghum* . . . . . . . . . . . . . . 9,837Barley . . . . . . . . . . . . . . . . . 6,791Oats. . . . . . . . . . . . . . . . . . . 3,793Rice . . . . . . . . . . . . . . . . . . . 2,833Sunflower . . . . . . . . . . . . . . 2,504Peanuts . . . . . . . . . . . . . . . . 1,637Dry Edible Beans . . . . . . . . 1,600Sugar Beets. . . . . . . . . . . . . 1,413Potatoes . . . . . . . . . . . . . . . 1,317Sugar Cane . . . . . . . . . . . . . . 948Tobacco . . . . . . . . . . . . . . . . . 747Rye . . . . . . . . . . . . . . . . . . . . . 381

Other. . . . . . . . . . . . . . . . . 47,830Safflower. . . . . . . . . . . . . 292Flaxseed . . . . . . . . . . . . . 191Canola. . . . . . . . . . . . . . . 187Dry Edible Peas . . . . . . . 145Lentils . . . . . . . . . . . . . . . 143Peppermint Oil. . . . . . . . . 98Sweet Potatoes . . . . . . . . 79Hops . . . . . . . . . . . . . . . . . 43Spearmint Oil . . . . . . . . . . 32Mustard Seed . . . . . . . . . . 16Austrian Winter Peas. . . . 10Rapeseed . . . . . . . . . . . . . . 6

Source: USDA/National Agricultural Statistics Service

*Includes harvest for grain and silage

TM: A3–1C

WORLD CORN EXPORTS*



U.S.

59.3%

China

22.5%

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

TM: A3–1D

PARTS OF A

PERFECT FLOWER



Petal

Anther

FilamentStamen

Sepal

Receptacle

Pedicel

Ovary

Pistil

Stigma

Style

(Courtesy, Interstate Publishers, Inc.)

TM: A3–1E

POLLINATION



Pollen grains(contain sperm)

Stigma

Ovary

Ovule

Egg cell


TM: A3–1F

DOUBLE FERTILIZATION



PollenStigma

Ovary

Egg

One sperm fertilizes

second nucleus to form

endosperm

One sperm

fertilizes egg

Two sperm nuclei

Pollen tube

Egg nucleus

Second nucleus

1

2

3


TM: A3–1G

DICOT VS. MONOCOT SEEDS



Embryo

Embryo

Epicotyl

Epicotyl

Seed Coat

Seed Coat

Endosperm

SingleCotyledon

TwoCotyledons

Bean Seed (dicot) Corn Seed (monocot)


TM: A3–1H

PARTS OF A DEVELOPING

EMBRYO PLANT



PrimaryRoot

PrimaryRoot

Secondary Root

Hypocotyl

CotyledonEpicotyl


Understanding Sexual Reproduction · 2019-08-21 · Objective 2: Explain the difference between...

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