Transcript Ch 24 Plant Reproduction

1.
2.
3.
4.
Classify Which plant structures are male sexual
organs and which are female sexual organs
Apply Concepts Relate the characteristics of
angiosperms reproduction to angiosperm success
Review Define vegetative reproduction
Compare and Contrast Make a compare contrast
table comparing alternation of generations in
flowering plants and green algae (22.2)
CH 24 PLANT REPRODUCTION AND RESPONSE
24.1 Reproduction in Flowering Plants
Structure of Flowers

Reproductive organs that are composed of four
kinds of specialized leaves:
 Sepals,
petals, stamens, and carpels.
Sepals
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

Outermost circle of floral parts
Enclose the bud before it opens
Protect the flower while it is developing.
Petals


Found just inside the sepals
Colors, number, and shapes of such petals attract
insects and other pollinators to the flower.
Stamen

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
Male parts of the flower
Consists of a stalk called a filament with an anther
at its tip
Anther
 Structure
that produces pollen grains.
Carpels


Produce and shelter the female gametophytes and
seeds
Ovary
 Contains
one or more ovules where female
gametophytes are produced.
Carpels

Style
 Stalk

of carpel
Stigma
 Sticky
or feathery portion at tip of carpel to capture
pollen.
Carpel

Pistil
 Single
carpel or several fused carpels.
Angiosperm Life Cycle


Fertilization in angiosperms is distinct from other
plants
Two fertilization events take place- one produces
the zygote and the other a tissue, called
endosperm, within the seed.
Angiosperm Life Cycle


Alternation of generations between a diploid
sporophyte phase and a haploid gametophyte
stage
Male and female gametophytes live within the
tissues of the sporophyte.
Development of Male Gametophytes

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The male gametophytes (pollen grains) develop
inside anthers
Meiosis produces four haploid spore cells.
Development of Male Gametophytes
Each spore undergoes one mitotic division to
produce the two haploid nuclei of a single pollen
grain
 Two nuclei are surrounded by a thick wall that
protects the
male gametophyte.

Development of Female Gametophytes


Develop inside each carpel of a flower
Ovules (future seeds) are enveloped in a protective
ovary (future fruit).
Development of Female Gametophytes

Single diploid cell goes through meiosis to produce
four haploid cells, three of which disintegrate.
Development of Female Gametophytes


Remaining cell undergoes mitosis, producing eight
nuclei
Embryo sac
 Eight
nuclei and the surrounding membrane.
Development of Female Gametophytes

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
Cell walls form around six of the eight nuclei
One of the eight nuclei near the base of the
gametophyte, is the nucleus of the egg (female
gamete)
Will fuse with male gamete, form zygote and
become sporophyte if fertilization occurs.
Pollination

Transfer pollen to the female portions of the
flower
 Can

use wind or an animal pollinator
Wind pollination is less efficient
 Relies
on favorable weather and sheer numbers of
pollen grains.
Animal Pollinated Plants

Variety of adaptations to attract and reward
animals
 Such
as bright colors and sweet nectar
 Animals have evolved body shapes to reach nectar
deep within certain flowers

Insect pollination
 Plant
benefits- efficient pollination
 Insect benefits- source of food.
Fertilization

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Pollen grain lands on the
stigma of a flower
Pollen tube begins to grow
Pollen grain has two cells
1.
2.
Cell divides and forms two
sperm cells
Cell becomes the pollen
tube.
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
Pollen tube grows into the style
Reaches the ovary
Enters an ovule.
Double Fertilization
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One of the sperm nuclei fuses with the egg nucleus
to produce a diploid zygote
Other sperm nucleus fuses with two polar nuclei in
the embryo sac to form a triploid (3N) cell or
endosperm
Endosperm
 Food-rich
tissue known which nourishes the seedling
as it grows.


Flowering plant spends very little in the way of
food resources on producing seeds from ovules
until double fertilization has actually taken place
Make more seeds.
Vegetative Reproduction
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

Asexual reproduction
Enables a single plant to produce offspring
genetically identical to itself by mitosis
Enables a single plant to produce offspring
genetically identical to itself by mitosis.


New plants may grow from roots, leaves, stems, or
plantlets
Single plant can reproduce quickly.
Good

Single plant produces genetically identical
offspring, enabling well-adapted individuals to
rapidly fill a favorable environment.
Bad

Does not produce new combinations of genetic
traits, which may be valuable if conditions in the
physical environment change.

Grafting
 Method
to reproduce
seedless plants and varieties
of woody plants that cannot
be propagated from cuttings
 Plants need to be closely
related.