Download Sexual and Asexual Reproduction of Plants oVERVIEW

Sexual and Asexual Reproduction of Plants
OVERVIEW
INSTRUCTOR:
UNIT: Performance of Technical Skills Related to Plant and Soil Science and Technology
LESSON:
Sexual and Asexual Reproduction of Plants
IMS REFERENCE: IMS #8388
LESSON PLAN
LESSON OBJECTIVES
The student will be able to:
 discuss the sexual reproduction (pollination and fertilization) of flowering plants;
 explain asexual (vegetative) methods of propagating plants; and
 propagate plants sexually and asexually.
TOOLS & EQUIPMENT
 Computer(s) with internet access
KEY TERMS
egg
rootstock
scion
sperm
zygote
SUPPLEMENTAL MATERIALS & RESOURCES
 IMS #8388
 Class Notes sheets for IMS #8388
 Lesson Test for IMS #8388
 horticultural and agronomic plant specimens
 bean seeds
 dissection tools
 live plant flowers containing both stamens and pistils
 vegetable and/or bedding plant seeds
 containers and growing medium for planting seeds
 plants for demonstrating and performing the plant propagation techniques of cuttings,
layering, separation, division, grafting, budding, etc.
TEACHING PROCEDURES
 Preparation
Key Points
Link:
Methods
Why do plants need to reproduce themselves? What would be Student Thought and Discussion
the consequences if they didn’t?
(Student discussion may include that plant reproduction
is necessary for the survival and perpetuation of plant
species. If plants did not reproduce, plant species would
die out. Plants are an important source of food and
oxygen for the existence of other living species.
Without them, life would cease to exist.)
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Sexual and Asexual Reproduction of Plants
Motivation:
Display of Plant Specimens
Provide a variety of plant specimens for display.
Throughout the lesson, have students identify each of
the plant specimens and determine how each is capable
of reproducing – whether by sexual and/or asexual
means.
Overview:
Review of objectives
In this lesson, the students will:
 discuss the sexual reproduction (pollination and
fertilization) of flowering plants;
 explain asexual (vegetative) methods of propagating
plants; and
 propagate plants sexually and asexually.
 Presentation
Key Points
Methods
Although animals can only reproduce sexually, plants
have the capability to propagate or multiply themselves
by means of sexual and/or asexual reproduction.
Teacher-led discussion
What are the benefits of plants being able to reproduce by both
sexual and asexual means?
Student thought and discussion
Sexual reproduction involves using seeds to produce
new plants.
Presentation A
Asexual or vegetative reproduction includes using plant
parts other than seeds to produce new plants.
Agronomic and horticultural crops reproduced primarily
by seeds include:
 field crops (corn, wheat, rice, sorghum)
 flowering greenhouse and bedding plants
 vegetable transplants
Horticultural crops and plants produced quicker and
more efficiently by vegetative means include:
 landscape & ornamental plants (flowering perennials,
groundcovers, shrubs)
 turfgrasses
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Sexual and Asexual Reproduction of Plants
 fruit crops
Presentation B
Sexual Reproduction
Seeds are the means by which plants sexually reproduce.
Although seeds contain the genetic characteristics of the
parent plant, characteristics of plants grown from seeds
may vary from the parent plant.
Seed propagation:
 is an economical and widely used method of
producing new plants.
 allows a grower to produce a large number of plants.
Pollination and fertilization are part of the sexual
process that occurs within the flowers or reproductive
structures of a plant. These processes result in the
formation and development of seeds.
A seed consists of a:
 tiny plant,
 supply of stored food, and
 a protective covering.
Complete Seed Dissection and Identification Activity at
this time.
Application #1
Pollination occurs when mature pollen grains (male sex
cells) from the stamen come into contact with the moist,
sticky surface of a flower stigma (female flower part).
(Demonstrate the process of self-pollination and crosspollination using flowers of a live plant that contains
both stamens and pistils.)
Teacher demonstration
Self-pollination occurs when pollen comes into contact
with a stigma within the same flower or other flowers on
the same plant.
Cross-pollination occurs when pollen from the flower of
one plant transfers to the stigmas of flowers on another
plant.
Pollen grains transfer to flower stigmas by means of:
 gravity
 insects
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Sexual and Asexual Reproduction of Plants
 wind
 animals
After a pollen grain anchors on the moist, sticky surface
of a flower stigma, it germinates and produces a pollen
tube. The pollen tube grows down through the style and
into the ovary where it eventually reaches an ovule.
During the fertilization process:
 one sperm cell from the pollen tube unites with the
egg cell in the ovule to form a zygote.
 the second sperm cell from the pollen tube unites
with two separate polar nuclei to form a primary
endosperm nucleus.
 double fertilization results from the unions of the two
male sex cells.
The zygote formed through the union of the sperm and
egg cells proceeds through cell division and develops
into a seed embryo.
The primary endosperm nucleus develops to form a food
source to be used by the embryonic plant during seed
germination.
For each seed a plant produces, a separate grain of
pollen must reach and unite with an ovule.
Begin Seed Germination Activity at this time.
Application #2
Asexual Reproduction
Presentation C
Asexual or vegetative reproduction involves the
production of new plants by means of using vegetative
parts of an existing plant.
The vegetative parts of many plants have the ability to
produce new roots and/or shoots to form a new plant.
Asexual reproduction is often advantageous over sexual
reproduction because:
 new plants reach maturity in less time.
 disease-free plants can be produced in controlled
environmental conditions.
 reproduction is possible for plants that do not
develop reproductive parts or viable seeds.
 plant selection for desired characteristics is more
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Sexual and Asexual Reproduction of Plants
reliable.
 new plants are genetically identical to the parent
plant.
Vegetative plant parts used in asexual reproduction
include:




leaves
stems (above-ground, below-ground)
buds
roots
Methods of vegetative plant reproduction include:







cuttings
layering
separation
division
grafting
budding
tissue culture
Propagation by cuttings is the most widely used method
of vegetative or asexual reproduction. A cutting is any
plant part severed from the parent plant.
Cuttings include:
 stem cuttings (portion of a stem that includes a node)
 root cuttings (2- to 3-inch section of thickened root)
 leaf cuttings (leaf blade and petiole, leaf blade only,
or section of leaf blade)
Layering involves forcing a vegetative plant part to form
roots while still attached to the parent plant.
Two types of layering are:
 air layering (forcing roots to form on a stem, outside
the soil)
 ground layering (extending a plant part into the
ground, covering it with soil, and allowing it to root)
Separation involves removing new plants formed on
specialized stems and separating them from the parent
plant.
Division is the technique of cutting specialized plant
structures into sections and forcing each section to grow
into a new plant.
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Sexual and Asexual Reproduction of Plants
Practice asexual propagation techniques at this time.
Grafting consists of uniting a hardwood scion from one
plant with the rootstock of another similar hardwood
plant to form a vascular connection between the two
plant parts.
Budding, similar to grafting, consists of removing buds
from one plant and placing them on stems of other
closely related plants to form a vascular connection
between the two plant parts.
Teacher demonstration
Tissue culture, or micro-propagation, involves placing a
very small piece of plant tissue on a sterilized culture
medium. Under sterile conditions, the plant tissue
multiplies and grows into new plants.
Advantages of tissue culture as a means of asexual
reproduction are that it:
 allows large numbers of offspring to be produced
quickly;
 allows growers to produce disease-free plants;
 is a cost-efficient method of reproducing plants; and
 allows plants to be produced that have the same
characteristics as the parent plant.
Disadvantages of tissue culture include:
 the costs of necessary tools and equipment;
 the preciseness of establishing and maintaining
sterile conditions needed for plant development; and
 the requirement of additional time and labor as
compared to other methods of asexual propagation.
Begin Asexual Propagation Activity at this time.
Application #3
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Sexual and Asexual Reproduction of Plants
Evaluation #2
 Application
Key Points
Seed Dissection and Identification
Methods
Dissect a bean seed and identify the embryonic plant,
stored food supply for germination, and the protective
seed covering.
Student Activity
Seed Germination Activity
Student Activity
Sow vegetable and/or bedding plant seeds in flats, individual
containers, or in a class garden. As the seeds germinate and the
plants begin to grow, refer to the benefits of sexual reproduction
as a means of plant propagation.
Asexual Propagation Activity
Perform a variety of asexual propagation techniques using a
Student Activity
variety of plants. Record observations of root development and
plant growth.
 Evaluation/Summary
Key Points
Complete Lesson Test for IMS #8388
Methods
Worksheet
REFERENCES/ ADDITIONAL MATIERIALS
Poincelot, Raymond P. Horticulture: Principles and Practical Applications. Englewood Cliffs,
NJ: Prentice-Hall, Inc., 1980.
Texas Cooperative Extension Service. Master Gardener Handbook. 3rd edition. College Station,
TX. 1995.
Web site references:
http://plantfacts.ohio-state.edu/mg/manual/prop.htm
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Sexual and Asexual Reproduction of Plants
http://aggie-horticulture.tamu.edu/propagation/propagation.html
http://ag.arizona.edu/pubs/garden/mg/propagation/
COLLEGE & CAREER READINESS STANDARD
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