horticulture science lesson 14 examining sexual reproduction of flowering plants

Horticulture Science Lesson 14

Examining Sexual Reproduction of Flowering Plants

Horticulture Science Lesson 14

Examining Sexual Reproduction of Flowering Plants

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Interest ApproachInterest ApproachBring 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.


Student Learning ObjectivesStudent Learning Objectives•Discuss the importance of plant propagation.

•Explain the difference between sexual and asexual propagation.


Student Learning ObjectivesStudent Learning Objectives

•Identify the major parts of a seed.

•List the function of each major part of a seed.


TermsTerms• cotyledon• cross-pollination• diploid• double fertilization• embryo• endosperm• epicotyl• fertilization

TermsTerms• gametes• germination• haploid• hybridization• hybrids• hypocotyls• incompatibility• plumule

TermsTerms• pollination• polyploid• radicle• seed• seed coat• self-pollination• sexual reproduction• zygote

What would happen if plants did not have the ability to reproduce?

• Plants are essential for life as we know it on earth.

• 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.

What would happen if plants did not have the ability to reproduce?

• Throughout history, people have relied on seeds and plant parts to grow new plants for food and fiber.

• 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.

How is sexual reproduction different from asexual reproduction and what

is the advantage of sexual reproduction?

• Sexual reproduction occurs when the male sperm carried in the pollen unites with the female egg within a flower.



• 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.



• 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.



• 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.



• 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.

• Many grasses and flowering plants have three or more sets of chromosomes. They are called polyploid.



• 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).

• 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.



• 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.



• When the pollen of a plant pollinates a flower on the same plant, it is called selfpollination.

• A plant with genetic mechanisms that prevent its pollen from growing a pollen tube on a style of the same plant has a condition called incompatibility.

• When the pollen of a plant pollinates the flower on another plant of the same species, it is called cross-pollination.

What are the major parts of a seed and where are they located

within the seed?• 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.


within 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.


within the seed?• 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.


within the seed?• The embryo and endosperm (cotyledon in

some plant species) is surrounded by the protective seed coat.

• It plays an important role in determining when outside conditions are right for germination, the beginning of growth.

What is the function of each major part of a dicot seed and a

monocot seed?

• Each part of a seed has a specific function to help ensure that a healthy new plant will emerge from the seed.

• The seed is a living entity which contains the embryo plant and everything necessary for its growth and development.


monocot seed?

• Dicot plants (e.g., soybean, pea, oak) have two cotyledons, or seed leaves, in their seed.

• Monocot plants (e.g., corn, coconut, lily) have one cotyledon in their seed.


monocot seed?

• 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.

• The hypocotyl of the embryo plant develops into the true stem.


monocot seed?

• 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.


monocot seed?


monocot seed?• 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.

• The cotyledon stores food absorbed from the endosperm when the seed was formed.


monocot seed?

• The cotyledon also 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.

• The seed coat surrounds the seed and protects it from injury and dehydration.

Review/SummaryReview/Summary•What would happen if plants did not have the ability to reproduce?

•How is sexual reproduction different from asexual reproduction and what is the advantage of sexual reproduction?

Review/SummaryReview/Summary•What are the major parts of a seed and where are they located within the seed?

•What is the function of each major part of a dicot seed and a monocot seed?