Transcript Sexual Reproduction

Horticulture Science
Lesson 14
Examining Sexual Reproduction of
Flowering Plants
Interest Approach
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.
Student Learning Objectives
•Discuss the importance of
plant propagation.
•Explain the difference
between sexual and asexual
propagation.
Student Learning Objectives
•Identify the major parts of a
seed.
•List the function of each major
part of a seed.
Terms
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cotyledon
cross-pollination
diploid
double fertilization
embryo
endosperm
epicotyl
fertilization
Terms
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gametes
germination
haploid
hybridization
hybrids
hypocotyls
incompatibility
plumule
Terms
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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.
How is sexual reproduction different
from asexual reproduction and what
is the advantage 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.
How is sexual reproduction different
from asexual reproduction and what is
the advantage of sexual reproduction?
• 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.
How is sexual reproduction different
from asexual reproduction and what is
the advantage of sexual reproduction?
• 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.
How is sexual reproduction different
from asexual reproduction and what is
the advantage of sexual reproduction?
• 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.
How is sexual reproduction different
from asexual reproduction and what is
the advantage of sexual reproduction?
• 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.
How is sexual reproduction different
from asexual reproduction and what is
the advantage of sexual reproduction?
• 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.
How is sexual reproduction different
from asexual reproduction and what is
the advantage of sexual reproduction?
• Pollination is the
transfer of the male
sperm carried in
the pollen to the
female part of the
flower, the stigma.
How is sexual reproduction different
from asexual reproduction and what is
the advantage of sexual reproduction?
• 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.
How is sexual reproduction different
from asexual reproduction and what is
the advantage of sexual reproduction?
• 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.
What are the major parts of a seed
and where are they located
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.
What are the major parts of a seed
and where are they located
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.
What are the major parts of a seed
and where are they located
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.
What is the function of each
major part of a dicot seed and a
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.
What is the function of each
major part of a dicot seed and a
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.
What is the function of each
major part of a dicot seed and a
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.
What is the function of each
major part of a dicot seed and a
monocot seed?
What is the function of each
major part of a dicot seed and a
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.
What is the function of each
major part of a dicot seed and a
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/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/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?