Transcript Chapter 30 Plant Reproduction Table of Contents Section 1 Plant Life Cycles Section 2 Sexual Reproduction in Flowering Plants Section 3 Dispersal and Propagation.

Chapter 30
Plant Reproduction
Table of Contents
Section 1 Plant Life Cycles
Section 2 Sexual Reproduction in Flowering Plants
Section 3 Dispersal and Propagation
Chapter 30
Section 1 Plant Life Cycles
Objectives
• Describe the life cycle of a moss.
• Describe the life cycle of a fern.
• Describe the life cycle of a gymnosperm.
• Compare homospory and heterospory.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Mosses
• The life cycle of mosses alternates between
clumps of gametophytes (the dominant
generation) and a sporophyte that consists of a
spore capsule on a bare stalk.
• Moss gametophytes produce gametes in two
types of reproductive structures: antheridia
(singular, antheridium), and archegonia (singular,
archegonium).
Chapter 30
Section 1 Plant Life Cycles
Alternation of Generations
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Visual Concept
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Mosses, continued
• An antheridium is a male reproductive structure that
produces hundreds of flagellated sperm by mitosis.
• An archegonium is a female reproductive structure that
produces a single egg by mitosis.
• Sperm break out of the antheridia and swim to
archegonia. One sperm fertilizes one egg to produce a
diploid zygote.
• The zygote undergoes repeated mitotic division and
forms a sporophyte, which remains on the
gametophyte.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Mosses, continued
• Soon, the cells at the tip of the sporophyte will
form a sporangium, called a capsule.
– A capsule of a moss is the part of the
sporophyte that will create haploid spores.
• Mosses will only produce one type of spore.
When only one type of spore is produced it is
called homospory.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Mosses, continued
• When the spores are mature, the capsule will split
open, and the spores are carried away by the
wind.
• Spores that land in favorable environments may
germinate and grow into new gametophytes.
Chapter 30
Life Cycle of
a Moss
Section 1 Plant Life Cycles
Chapter 30
Section 1 Plant Life Cycles
Life Cycle of Mosses
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Visual Concept
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Ferns
• The life cycle of ferns is similar to mosses, but it
is also different.
• Most ferns are homosporous and produce a
sporophyte that grows from the gametophyte.
• However, the sporophyte, not the gametophyte, is
the dominant generation in ferns.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Ferns, continued
• The fern’s gametophytes are tiny and are
anchored to the soil by rhizoids. They can
produce both antheridia and archegonia.
• Water must be present in order for the egg to be
fertilized.
• Once the egg is fertilized, it will soon form a
zygote and then a sporophyte.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Ferns, continued
• Once the sporophyte can survive on its own, the
gametophyte will die.
• Once mature, a fern sporophyte will have leaves
that are called fronds.
• Fronds grow from an underground stem, or
rhizome, and contain cells on their underside that
develop into sporangia.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Ferns, continued
• In many ferns, the sporangia on the underside of
a frond are clustered together.
– A cluster of sporangia is called a sorus. The
sorus will produce haploid spores.
• Once the spores have matured, they will be
carried away by air currents. When the spores
land, they may grow into new gametophytes.
Chapter 30
Life Cycle of
a Fern
Section 1 Plant Life Cycles
Chapter 30
Section 1 Plant Life Cycles
Life Cycle of Ferns
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Visual Concept
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Gymnosperms
• Gymnosperms will produce two types of spores—
male microspores and female megaspores.
– Microspores will grow into male
gametophytes, and megaspores will grow into
female gametophytes.
• When different types of asexual spores are
produced it is called heterospory.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Gymnosperms, continued
• The microspores of heterosporous plants
produce male gametophytes that stay attached to
the sporophyte and develop into pollen.
• Pollen allows sexual reproduction in seed plants
to take place independent of seasonal rains or
other periods of moisture.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Gymnosperms, continued
• However, gymnosperm sexual reproduction can
take more than two years.
• During the first summer, a mature pine tree
produces separate female and male cones, which
produce male (microsporangia) and female
(megasporangia) sporangia.
• The following spring, the cells in all sporangia
undergo meiosis and divide to produce haploid
spores.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Gymnosperms, continued
• Megasporangia are haploid spores that produce
megaspores, which develop into megagametophytes, or
female gametophytes.
– A thick layer of cells called an integument surrounds
and protects each megasporangium.
– Each integument has a small opening where pollen can
enter, called the micropyle.
– Together, a megasporangium and its integument
form a structure called an ovule.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Gymnosperms, continued
• Microsporangia produce microspores, which
develop into microgametophytes, or male
gametophytes.
– A pollen grain is a microgametophyte of a seed
plant.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Gymnosperms, continued
• The male cones of a pine release huge numbers of
pollen grains into the wind.
• When the pine pollen lands on a female cone, it will
drift between the cone scales until they reach the
ovules.
• The transfer of pollen, the male gametophyte, to
ovules, the female gametophyte, is called
pollination.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Gymnosperms, continued
• During pollination, the pollen grain is drawn into
the ovule through the micropyle, and induces the
ovule to produce archegonia and eggs.
• After pollination, the pollen grain begins to grow a
pollen tube.
– The pollen tube is a slender extension of the
pollen grain that enables sperm to reach an egg.
Chapter 30
Section 1 Plant Life Cycles
The Life Cycle of Gymnosperms, continued
• Pine sperm do not have flagella and they do not
swim to an egg. The pollen tube carries the
maturing sperm to the egg.
• When the pollen tube reaches an archegonium,
one sperm unites with an egg to form a zygote.
• Over the next few months, the zygote develops into
an embryo as the ovule matures into a seed.
Chapter 30
Life Cycle of
a Conifer
Section 1 Plant Life Cycles
Chapter 30
Section 1 Plant Life Cycles
Life Cycle of Conifers
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Visual Concept
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Objectives
• Identify the four main flower parts, and state the
function of each.
• Describe gametophyte formation in flowering plants.
• Relate flower structure to methods of pollination.
• Describe fertilization in flowering plants.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Parts of a Flower
• Early land plants lacked leaves and roots and
consisted of only stems.
• Leaves evolved from branches of stems, and
flowers are considered to be highly specialized
branches and the parts of a flower to be
specialized leaves.
• The specialized leaves of a flower form on the
swollen tip of a floral “branch”, which is called a
receptacle.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Parts of a Flower, continued
• Flower parts are usually found in four concentric
whorls, or rings.
• The outer whorl is called the sepals, which protects
the other parts of a developing flower before it
opens.
• Petals make up the next whorl, and can vary
drastically between plants. Some plants have
brightly colored petals, and other plants have petals
that are small or absent.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Parts of a Flower, continued
• The male reproductive structures are stamens,
each of which consists of an anther and a
filament, and are found on the third whorl of the
flower.
– An anther contains microsporangia, which
produce microspores that develop into pollen
grains.
– A stalklike filament supports an anther.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Parts of a Flower, continued
• The innermost whorl contains the female
reproductive structures, which are called carpels.
• One or more carpels fused together make up the
structure called a pistil, which is the main female
reproductive structure in flowering plants.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Parts of a Flower, continued
– The base of a pistil contains the ovary, which
will produce eggs in ovules.
– A style, which is usually stalklike, rises from
the ovary.
– The tip of the style is called the stigma, which
usually is sticky or has hairs in order to trap
pollen grains.
Chapter 30
Floral Structure
Section 2 Sexual Reproduction
in Flowering Plants
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Parts of a Flower
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Visual Concept
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Parts of an Angiosperm
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Visual Concept
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Gametophyte Formation
• In angiosperms, gametophytes develop within the
reproductive structures of flowers.
• Embryo sacs, which are the female gametophytes
in angiosperms, form within the ovary of the
pistil.
• Pollen grains, the male gametophytes, form
within the anthers of the stamens.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Gametophyte Formation, continued
Embryo Sac Formation
• In flowers, ovules form in the ovary of a pistil.
• An angiosperm ovule consists of a
megasporangium surrounded by two
integuments, which do not completely enclose
the megasporangium.
• At one end of the ovule is the micropyle, through
which a pollen tube can enter.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Gametophyte Formation, continued
Embryo Sac Formation, continued
• An ovule contains a large diploid cell called a
megaspore mother cell.
• A megaspore mother cell undergoes meiosis and
produces four haploid megaspores.
• The maturing megaspore undergoes three mitotic
divisions, which produce a cell that has eight
haploid nuclei.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Gametophyte Formation, continued
Embryo Sac Formation, continued
• The haploid, megaspore nuclei migrate to
certain locations within the cell.
• The nuclei are initially arranged in two groups
of four at the top and bottom of the cell.
• Two nuclei will come to the center from the
ends or poles and are called polar nuclei.
These are the nuclei that will eventually fuse
with the sperm cells.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Gametophyte Formation, continued
Embryo Sac Formation, continued
• The other six nuclei within the megaspore mother
cell help the polar nuclei be fertilized by the sperm
and then eventually die after fertilization occurs.
• The megaspore mother cell is now called the
embryo sac and contains eight nuclei—seven
smaller cells and a large central cell that encloses
all the other cells.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Gametophyte Formation, continued
Embryo Sac Formation, continued
• The embryo sac is also known as the mature
female gametophyte, or megagametophyte.
• The surrounding integuments and the embryo
sac now form a mature ovule, which when
fertilized will develop into a seed.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Formation of A Female Gametophyte
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Ovule Formation in an Angiosperm
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Visual Concept
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Gametophyte Formation, continued
Pollen Grain Formation
• An anther contains four microsporangia, or
pollen sacs.
• Initially, the pollen sacs contain many diploid
cells, and are called microspore mother cells.
• Each of these microspore mother cells will
undergo meiosis and produce four haploid
microspores.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Gametophyte Formation, continued
Pollen Grain Formation, continued
• Each microspore undergoes mitosis and
produces two haploid cells that do not separate.
• Once the cells are haploid, a thick wall then
develops around the microspore.
– The resulting two-celled structure is a pollen
grain, which is the male gametophyte,
or microgametophyte.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Gametophyte Formation, continued
Pollen Grain Formation, continued
• The larger of the two cells is the tube cell, from
which the pollen tube will form.
• The generative cell, which is enclosed in the tube
cell, will divide by mitosis to form two sperm.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Formation of A Male Gametophyte
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Pollen Grain Formation
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Visual Concept
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Parts of a Pollen Grain
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Visual Concept
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Pollination
• In flowering plants, pollination occurs when pollen
grains are transferred from an anther to a stigma.
• Pollination that involves just one flower, flowers on
the same plant, or flowers from two genetically
identical plants is called self-pollination.
• In contrast, pollination that involves two genetically
different plants is called cross-pollination.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Pollination, continued
• Flower structure promotes self-pollination in plants that
have flowers with petals that completely enclose both
the male and female flower parts.
• Pollen can be dispersed by water or air. The flowers of
such wind-pollinated angiosperms are small and lack
showy petals and sepals.
• Successful wind pollination depends on four conditions:
the release of large amounts of pollen, the ample
circulation of air or water, proximity of other plants that
it can pollinate, and dry weather.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Pollination, continued
• Bright petals and distinctive odors attract animals
that feed on pollen and nectar, a nourishing
solution of sugars.
• Many different kinds of animals can be pollinators.
• When these animals gather nectar, pollen sticks to
their bodies. As they collect more nectar, the
animals deposit some of the pollen on other
flowers. This is how the animals pollinate other
flowers.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Flowers and Animal Pollinators
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Visual Concept
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Fertilization
• For fertilization to occur in angiosperms, a pollen
grain must land on a stigma and then absorb
moisture. The pollen grain will then germinate.
• After fertilization, germination occurs.
Germination is when the tube cell forms a pollen
tube, and then grows through the stigma and
style to the ovary.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Fertilization, continued
• The pollen tube will grow into an ovule through
the micropyle on the ovary.
• After the pollen tube penetrates the ovule, two
sperm can travel through the pollen tube and
reach and fertilize the egg.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Fertilization, continued
• One of the two sperm will fuse with the egg and
form a diploid zygote, which will eventually
develop into an embryo.
• The second sperm fuses with the two polar
nuclei, producing a triploid (3n) nucleus. This
nucleus then develops into tissue called
endosperm.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Fertilization, continued
• The endosperm provides nourishment for the
embryo. Endosperm can be used up by the
developing embryo or be could still be on the
seed after the embryo is fully mature.
– This process of two cell fusions, which is
called double fertilization, is unique to
angiosperms.
Chapter 30
Section 2 Sexual Reproduction
in Flowering Plants
Fertilization of a Flower
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Visual Concept
Chapter 30
Life Cycle of an
Angiosperm
Section 2 Sexual Reproduction
in Flowering Plants
Chapter 30
Section 3 Dispersal and
Propagation
Objectives
• Describe adaptations for fruit and seed dispersal.
• Name the three major categories of fruits.
• Compare the structure and germination of different
types of seeds.
• Recognize the advantages and disadvantage of
asexual reproduction.
• Describe human methods of plant propagation.
Chapter 30
Section 3 Dispersal and
Propagation
Dispersal of Fruits and Seeds
• One reason for the success of the seed plants is
the development of structures that are adapted
for dispersing offspring—fruits and seeds.
• Fruits and seeds are dispersed by animals, wind,
water, forcible discharge, and gravity.
• Gymnosperms do not produce fruits, but their
cones help protect seeds and aid in seed
dispersal.
Chapter 30
Section 3 Dispersal and
Propagation
Types of Fruits
• Botanists define a fruit
as a mature ovary.
• Many different types of
fruits have evolved
among the flowering
plants.
Chapter 30
Section 3 Dispersal and
Propagation
Types of Fruits, continued
• Fertilization usually initiates the development of
fruits.
• Fruits protect seeds, aid in their dispersal, and
often delay their sprouting.
• Fruits are classified mainly on the basis of two
characteristics: how many pistils or flowers form
the fruit, and whether the fruit is dry or fleshy.
Chapter 30
Section 3 Dispersal and
Propagation
Development of a Fruit
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Visual Concept
Chapter 30
Section 3 Dispersal and
Propagation
Structure of Seeds
• A seed is a plant embryo.
• A seed is protected and surrounded by a protective
coat called the seed coat.
• The structure of seeds differs among the major
groups of seed plants and non seed plants.
• Angiosperm seed structure differs between monocots
and dicots and differs when compared to
gymnosperm seeds.
Chapter 30
Section 3 Dispersal and
Propagation
Structure of Seeds, continued
• A dicot seed has many
parts.
• Between the two
cotyledons of a dicot
are the parts that make
up the rest of the
embryo.
Chapter 30
Section 3 Dispersal and
Propagation
Structure of Seeds, continued
• The parts of a dicot are the plumule, the epicotyl,
the hypocotyl, the radicle, and the hilum.
– The shoot tip, along with any embryonic
leaves, is called the plumule.
– The epicotyl extends from the plumule and is
attached the cotyledons.
Chapter 30
Section 3 Dispersal and
Propagation
Structure of Seeds, continued
• The parts of a dicot are the plumule, the epicotyl,
the hypocotyl, the radicle, and the hilum.
– The hypocotyl connects the cotyledons to the
radicle.
– The radicle is the embryonic root.
– The hilum is a scar that marks where the seed
was attached to the ovary wall.
Chapter 30
Section 3 Dispersal and
Propagation
Structure of Seeds, continued
• A monocot seed has
many of the same parts
as a dicot.
• One difference between
the two is that a
monocot seed does not
store nutrients like a
dicot does.
Chapter 30
Section 3 Dispersal and
Propagation
Structure of Seeds, continued
• A gymnosperm seed has
some of the same parts
as a seed plant.
• A difference between
gymnosperms and seed
plants is that a
gymnosperm has
needlelike cotyledons
instead of leaves.
Chapter 30
Seed Structure
Section 3 Dispersal and
Propagation
Chapter 30
Section 3 Dispersal and
Propagation
Structure and Function of Seeds
Chapter 30
Section 3 Dispersal and
Propagation
Seed Germination
• Although its embryo is alive, a seed will not
germinate, or sprout, until it is exposed to certain
environmental conditions.
• Many seeds will not germinate even when
exposed to conditions ideal for germination.
– These seeds exhibit dormancy, or a state of
reduced metabolism in which growth and
development do not occur.
Chapter 30
Section 3 Dispersal and
Propagation
Seed Germination, continued
Conditions Needed for Germination
• Most mature seeds are very dry and must absorb
water to germinate and grow.
• Many seeds also need light for germination, and
some even need certain or extreme temperatures
to germinate.
• In order to keep growing, the seed must get
oxygen.
Chapter 30
Section 3 Dispersal and
Propagation
Seed Germination, continued
Process of Germination
• The first visible sign of seed germination is the
emergence of the radicle.
• Soon after the radicle breaks the seed coat, the
shoot begins to grow.
• The type of seed determines how the shoot will
break through the ground.
Chapter 30
Section 3 Dispersal and
Propagation
Seed Germination, continued
Process of Germination, continued
• In some seeds the hypocotyl curves and
becomes hook-shaped. In these seeds, once the
hook breaks through the soil, the hypocotyl
straightens.
– This straightening pulls the cotyledons and the
embryonic leaves into the air, and they begin
photosynthesis.
Chapter 30
Section 3 Dispersal and
Propagation
Seed Germination, continued
Process of Germination, continued
• In contrast, other seeds remain underground and transfer
nutrients from the endosperm to the growing embryo.
• In these type of seeds, the plumule is protected by a sheath
that pushes through the soil.
• Once the sheath has broken through the soil surface, the
plumule grows up through the sheath and the first leaf
unfolds.
Chapter 30
Section 3 Dispersal and
Propagation
Seed Germination
Chapter 30
Section 3 Dispersal and
Propagation
Parts of a Seed
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Visual Concept
Chapter 30
Section 3 Dispersal and
Propagation
Asexual Reproduction
• Asexual reproduction is the production of an
individual without the union of gametes, and is
quite common in the plant kingdom.
• Asexual reproduction can be an advantage to
individuals that are well-adapted to their
environment.
• A disadvantage of asexual reproduction is the
lack of genetic variation among the offspring.
Chapter 30
Section 3 Dispersal and
Propagation
Asexual Reproduction, continued
• In nature, plants reproduce asexually in many
ways, including the development of spores and
vegetative reproduction.
– Vegetative reproduction is asexual
reproduction involving vegetative
(nonreproductive) parts of a plant, such as
leaves, stems, or roots.
– Many structures specialized for vegetative
reproduction have evolved in plants.
Chapter 30
Stems
Modified for
Vegetative
Reproduction
Section 3 Dispersal and
Propagation
Chapter 30
Section 3 Dispersal and
Propagation
Methods of Vegetative Plant Propagation
Chapter 30
Section 3 Dispersal and
Propagation
Propagation of Plants by Humans
• Many species of plants are vegetatively
propagated by humans from various plant
structures.
• People have also developed several methods of
propagating plants from other vegetative parts,
such as roots and even tissue samples.
• These methods include layering, grafting, and
using cuttings and tissue cultures.
Chapter 30
Section 3 Dispersal and
Propagation
Propagation of Plants by Humans, continued
Cuttings
• In some plants, roots will form on a cut piece of a stem, or
shoots will form on a piece of a root.
• Pieces of stems and roots that are cut from a plant and
used to grow new plants are called cuttings.
• Cuttings are widely used to propagate houseplants,
ornamental trees and shrubs, and some fruit crops.
Chapter 30
Section 3 Dispersal and
Propagation
Propagation of Plants by Humans, continued
Layering
• In some species roots will form on stems where
they make contact with the soil.
• People often stake branch tips to the soil or
cover the bases of stems with soil to propagate
such plants.
• The process of causing roots to form on a stem
is called layering.
Chapter 30
Section 3 Dispersal and
Propagation
Propagation of Plants by Humans, continued
Grafting
• Grafting is the joining of two or more plant parts to form a
single plant, by attaching a bud or small stem of one plant to
the roots or stems of a second plant.
• Grafting enables the desirable characteristics of two cultivars
to be combined.
• Grafting is used to propagate fruit and nut trees and many
ornamental trees and shrubs.
Chapter 30
Section 3 Dispersal and
Propagation
Propagation of Plants by Humans, continued
Tissue Culture
• The production of new plants from pieces of
tissue placed on a sterile nutrient medium is
called tissue culture.
• Unlike most animal cells, plant cells contain
functional copies of all the genes needed to
produce a new plant. Thus, it is possible for a
whole plant to regrow from a single cell.
Chapter 30
Section 3 Dispersal and
Propagation
Propagation of Plants by Humans, continued
Tissue Culture, continued
• Because plants can be grown by using tissue
cultures, millions of identical plants can be grown
from a small amount of tissue.
• Tissue culture is used in the commercial
production of orchids, houseplants, cut flowers,
fruit plants, and ornamental trees, shrubs, and
nonwoody plants.
Chapter 30
Section 3 Dispersal and
Propagation
Parts of Plants Eaten as Food
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