PLANT
REPRODUCTION
Plant Reproduction
What Are the Basic Features of Plant Life Cycles?
How Is Reproduction in Seed Plants Adapted to Drier
Environments?
What is the Function and Structure of the Flower?
Terms to Know
• Haploid: having a single set of chromosomes
in each cell.
• Diploid: having two sets of chromosomes in
each cell.
• Mitosis: cell division, which produces two
genetically identical cells.
• Meiosis: reduction division, which produces
four haploid reproductive cells.
Plants and Animals
Plant Reproduction Animal Reproduction
Life cycle
Alternation of
generations
No alternation of
generations
Gametes
Haploid (n) gametes
Haploid gametes
Spores
Haploid (n) spores
No spores
Gametes made Haploid gametophyte,
by
by mitosis
Diploid organism, by
meiosis
Diploid sporophyte, by
Spores made by
meiosis
No spores
REPRODUCTION!
• Asexual Reproduction
•
involves only 1 parent
•
offspring genetically
identical to parent
• Sexual Reproduction
•
involves 2 parents
•
involves regular body
cells
•
offspring genetic mix of
both parents
•
its quick
•
involves specialized sex
cells
•
its slow
1:21
Asexual Reproduction
• Binary fission
• happens in bacteria, amoeba, some algae
• one parent cell splits into 2 identical
daughter cells
• Budding
• happens in yeast, hydra, corals
• parent produces a bud
• bud gets detached and develops into
offspring which is identical to parent
Binary Fission
Rod-Shaped Bacterium,
hemorrhagic E. coli
Budding
Spore Formation
Fern
Fungi
Vegetative
Reproduction
Sexual Reproduction in Animals
• involves specialized sex cells called gametes
• the union of a male and female gamete results
in the formation of a zygote that develops into a
new individual
Sexual Reproduction
in Plants
Male
Parts
Female
Parts
(Pistil)
pollen (male) + ovule (female) → single-celled zygote → multi-celled
embryo (contained in a seed) → new individual
Sexual Reproduction in Plants
• stamen is the male part and contains pollen
• carpels or pistil is the female part and
contains ovule (eggs)
• pollen grains from the anther are transferred to
the stigma by the process of pollination
• self pollination (plant pollinates its own eggs)
• cross pollination (pollen from one plant
pollinates another plants eggs)
Pollination
• flowers are designed to lure insects to
help with the pollination process
• also wind, animals, birds can transport
pollen
Sexual Reproduction Summary
Male
Gamete
Female
Gamete
Type of Result of
Union
Union
Final
Result
Plants
pollen
ovule
(egg)
pollination
single cell
zygote
multi-cell
embryo
(in seed)
Animals
sperm
egg
fertilization
single cell
zygote
multi-cell
embryo
Some Organisms do Both
• most plants that produce seeds (sexual
reproduction) can also reproduce asexually by
things like cuttings or runners
• this gives them an advantage for survival
sponges and
hydra
mosses
Which is Better?
It depends!
Asexual Reproduction
Sexual Reproduction
• advantages
• advantages
•
•
•
does not require special
cells or a lot of energy
•
can produce offspring
quickly
lots of variation within a
species
•
in a stable environment
creates large, thriving
population
able to live in a variety of
environmental settings
•
able to adapt to changes
in the environment
• disadvantages
• disadvantages
•
limited ability to adapt
•
needs time & energy
•
face massive die-off if
environment changes
•
produce small populations
Asexual Reproduction
• Natural “cloning.” Genetically Identical.
• Fast, no mate required.
• Beneficial for plants that must compete for
scarce resources (Stable Environs).
• Part of a single plant divides by mitosis to give
rise to a new plants.
•
•
•
Spreading of runners (strawberries)
Production of bulbs (daffodils)
Sprouting of rhizomes (irises)
Sexual Reproduction
• Fusion of egg and sperm cells (haploid), from
meiosis, gamete formation and fertilization.
• May be limited to a certain season.
• Slower than asexual reproduction.
• Allows genetic mixing, increasing variability in
a population. Two parents give rise to
genetically variable offspring. Favored in
variable environments.
Alternate “Generations”
• All plant life cycles are characterized by alternating
of portions (haploid-to-diploid-to-haploid).
• Multicellular diploid plants (sporophytes) and
multicellular haploid plants (gametophytes) take turns
producing each other during the reproductive life
cycle.
• Sporophyte: diploid (2n), produce haploid spores
by meiosis.
• Gametophyte: haploid (n), produce gametes by
mitosis.
Life Cycle
Life Cycle
• Diploid sporophyte (spore-forming plant) produces
haploid spores by meiosis.
• Spore germinates (begins to grow and develop); divides
repeatedly by mitosis forming a haploid gametophyte
(gamete-forming plant).
• Gametophyte produces haploid sperm and eggs by
mitosis (gametes are produced at different times to
prevent self-fertilization).
Life Cycle
• Sperm and egg fuse to form a diploid zygote
(fertilized egg).
• Zygote undergoes repeated mitosis to form a new
diploid sporophyte plant.
Non-Flowering
Plants
• Mosses, ferns, and related plants have motile,
swimming sperm.
• Reproduction in these plants requires wet
conditions, and requires having male and
female parts close together.
• Living conditions, plant size, and genetic
mixing is limited.
Moss and Fern Life Cycles
Group 1: Seedless, Nonvascular Plants
•
Live in moist environments to
reproduce
•
Grow low to ground to retain
moisture (nonvascular)
•
Lack true leaves
•
Common pioneer species during
succession
•
Gametophyte most common
(dominant)
•
Ex: Mosses, liverworts,
hornworts
A. How Do Mosses/Liverworts Get Water?
1. Nonvascular plant
2. Only about 2 to 5 cm tall, cling to
damp soil, sheltered rocks, and the
shady side of trees
3. Leaves have only one or two cells
4. Rhizoids: root-like fibers that are on
the outside; take in water from
surroundings
Continue on to
A. How Do Mosses/Liverworts Get Water?
5. Spores: cells that can develop
into new organisms (seedless)
6. Close relative club mosses,
horsetails, ferns, and spike
mosses are VASCULAR
a. They grow thick and tall
Click this link to see pictures of moss and answer
Life Cycle of Mosses
1. Asexual reproduction: a plant
that needs only one type of cell
to reproduce
a. This process uses spores
2. Sexual reproduction: a plant
that needs two types of cells to
reproduce
a. This process completes the
cycle to allow reproduction
Continue on to next slide.
B. Life Cycle of Mosses
3. Alternation of
generations: process
of going from asexual
reproduction to sexual
reproduction
Moss Life Cycle
1)Moss
gametophytes
grow near the
ground
(haploid stage)
2) Through water,
sperm from the male
gametophyte will
swim to the female
gametophyte to
create a diploid
zygote
3) Diploid sporophyte
will grow from zygote
Diploid
sporophyte
4) Sporophyte will
create and release
haploid spores
...
zyg
egg
ote
zyg
egg
ote
zyg
egg
ote
male male
female
zyg
egg
ote
female female
male female
Haploid gametophytes
male
5) Haploid
spores land
and grow into
new
gametophytes
6) The process
repeats
ground
Haploid gametophytes
...
sporophyte
zyg
egg
ote
zyg
egg
ote
zyg
egg
ote
male male
female
zyg
egg
ote
female female
male female
Haploid gametophytes
male
Group 2: Seedless,
Vascular Plants
Vascular system allows
•
•
Taller growth
•
Nutrient transportation
Live in moist environments
•
•
Gametophyte stage
•
•
Male gametophyte: makes sperm
•
Female gametophyte: makes eggs
•
Sperm swims to fertilize eggs
Sporophyte stage
•
•
swimming sperm
•
Spores released into air
•
Spores land and grow into
gametophyte
Ex: Ferns, Club mosses, Horsetails
Parts of a Fern
1. Fronds: the front
leaves of ferns
2. Rhizome:
underground
stem which ferns
grow from; roots
sprout from this
Continue on to
Life Cycle of Ferns
1. Reproduce by
alternation of
generation; just
like mosses
2. Fern seeds are on
the fronds of the
ferns and scatter
on the ground
Click this link to see the
different types of ferns and
Fern Life Cycle
1) Sporophyte creates and releases haploid spores
Adult
Sporophyte
.
.
. .
ground
2) Haploid spores land in the soil
ground
3) From the haploid spores, gametophyte grows in the soil
Let’s zoom in
Fern
gametophytes
are called a
prothallus
ground
4) Sperm swim through water from the male parts (antheridium) to the female parts
(archegonia)…zygote created
Let’s zoom back out
zyg
egg
ote
zyg
egg
ote
zyg
egg
ote
5) Diploid sporophyte grows from the zygote
sporophyte
Fern
gametophytes
are called a
prothallus
ground
6) Fiddle head uncurls….fronds open up
7) Cycle repeats
-- Haploid spores created and released
.
.
fiddlehead frond
.
ground
.
2) Haploid spores land in the soil
ground
3) From the haploid spores, gametophyte (called the prothallus) grows in the soil
Let’s zoom in
ground
4) Sperm swim through water from the male antheridium to the female archegonia
Let’s zoom back out
zyg
egg
ote
zyg
egg
ote
zyg
egg
ote
5) Diploid sporophyte grows from the zygote
fiddlehead
sporophyte
ground
6) Fiddlehead uncurls….fronds open up.
7) Cycle repeats
.
.
.
ground
.
Review
1) Why do moss grow so low to the ground?
2) Which stage is the main stage of moss: sporophyte or
gametophyte?
3) How do moss reproduce?
4) What is the major difference between moss and ferns?
5) What are the leaves of ferns called?
6) What is needed for moss and ferns to reproduce?
7) Which stage is the main stage of ferns: sporophyte or
gametophyte?
8) What stage is created when sperm and egg fuse:
sporophyte or gametophyte?
Conifer Pollination
• Conifers (also non-flowering plants) have
reduced gametophytes.
• Male gametophyte is contained in a dry
pollen grain.
• Female gametophyte is a few cells inside of
the structures that become the seed.
Conifer Pollination
• Conifers are wind-pollinated plants.
• Chance allows some pollen to land on the
scales of female cones.
• Pollen germinates, grows a pollen tube into
the egg to allow sperm to fertilize the egg.
• Wind pollination is inefficient.
Pollen In-between
• Showy flowers are the
result of selection for more
efficient pollination
strategies.
• Flower parts are modified
leaves. Those that were
brightly colored attracted
insects in search of pollen.
• Pollen itself is a proteinrich food for insects. Some
plants offer other rewards,
such as nectar.
Seed Plant
Reproduction
•
43.2 How Is Reproduction in Seed Plants
Adapted to Drier Environments?
•
Seed plants (gymnosperms and angiosperms).
•
•
Gametophytes develop within sporophytes.
Reproduction can occur in dry habitats.
Seed Plant
Reproduction
•
Male gametophyte is surrounded by a protective
coat called a pollen grain.
•
The pollen grain encloses sperm cells in a watertight
packet that can be easily transported to another
plant.
•
Egg-producing female gametophyte remains moist
and protected within the sporophyte, and the pollen
grain ensures that the sperm are delivered directly to
the egg.
Seed Plant
Reproduction
•
The fertilized egg becomes enclosed in a droughtresistant seed.
•
Consists of an embryonic plant and a food
reserve encased within a protective outer coating.
•
May lie dormant up to years waiting for
conditions favorable for germination and growth.
Seed Plant
Reproduction
•
Non-flowering gymnosperms were the earliest seed
plants.
•
Gymnosperms bear male and female gametophytes
on separate cones.
•
Male cones release pollen grains that travel via wind
to female cones.
Flowers
Sexual Reproduction General
• Angiosperms produce flowers
• Flowers with both male and female reproductive
organs are perfect flowers.
• Flowers that have only male or only female
reproductive organs are imperfect flowers.
• Some angiosperms produce separate male and
female flowers (imperfect flowers).
• Monoecious plants
• Dioecious plants
Angiosperms
• Sexual reproduction involves flowers and
seeds.
• Flowering can be controlled by hormones,
genes and/or environmental factors
Flower Parts
Flower Structure
•
•
Evolution of the flower – purpose is attraction of pollinators.
•
A change from radial to bilateral symmetry.
•
Fusion or loss of whorls.
•
Odors and colors.
•
Nectar.
•
Oddly shaped petals
Flowers with 4 complete whorls = complete flower; flowers
missing 1 or more whorls = incomplete flower.
Incomplete flowers
• Flowers are complete if they have all
parts, and perfect if they have both male
and female parts.
• Grass flowers: incomplete, usually
imperfect (separate male and female
flowers)
• A tulip is complete (though the sepals
are the same color as the petals) and
perfect.
Imperfect flowers
Angiosperm Life
Cycle
Gametogenesis:
Male
Gametogenesis:
Female
Double Fertilization
Flower to Fruit
Ovule to Seed
Seed Germination
