Transcript Inquiry into Life Twelfth Edition

Chapter 10
Plant Reproduction
and Responses
Lecture Outline
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Co 10
10.1 Sexual Reproduction in Plants
• Alternation of generations
– Diploid (2n) sporophyte stage
• Produces spores by meiosis
• Spores divide by mitosis to become gametophytes
– Haploid (n) gametophyte stage
• Produces gametes by mitosis
• Upon fertilization, the cycle returns to 2n sporophyte
10.1 Sexual Reproduction in Plants
• In flowering plants, the sporophyte is dominant
and it is the generation that bears flowers
• Flowers produce two kinds of spores.
– Microspores undergo mitosis and becomes a pollen
grain, which is the male gametophyte
• Pollen grain contains two nonflagellated sperm
– Megaspores undergo mitosis to become a
microscopic embryo sac, which is the female
gametophyte
• Female gametophyte is retained within the flower
Alternation of Generations
in Flowering Plants
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anther
sporophyte
seed
diploid (2n)
ovule
ovary
zygote
FERTILIZATION
MEIOSIS
haploid (n)
microspore
egg
megaspore
sperm
Male gametophyte
(pollen grain)
Female gametophyte
(embryosac)
10.1 Sexual Reproduction in Plants
• Upon fertilization, a zygote is formed. The
zygote develops into an embryo
• A seed forms - contains the embryo and stored
food
• When a seed germinates, a new sporophyte
emerges
10.1 Sexual Reproduction in Plants
• Parts of a Flower
– Sepals - leaf-like structures that protect the
developing bud
– Petals - attract pollinators
– Stamens - male portion of the flower
• Anther - produces pollen grains
• Filament - a slender stalk that supports the anther
– Carpel - female portion of the flower
• Stigma - an enlarged stick knob
• Style - a slender stalk
• Ovary - encloses one or more ovules
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stamen
anther
carpel (pistil)
stigma
filament
style
ovary
petal
ovule
sepal
receptacle
peduncle
10.1 Sexual Reproduction in Plants
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stamen
• Flower parts occur in
threes (or multiples)
in monocots
s1
p2
carpel
s2
p1
petal
p3
sepal
s3
a. Daylily
• Flower parts occur in
four or fives (or
multiples) in eudicots
p3
p2
carpel
stamen
p4
petal
p1
p5
b. Festive azalea
a: © Farley Bridges; b: © Pat Pendarvis
10.1 Sexual Reproduction in Plants
• Flowers that have sepals,
petals, stamens and
carpels are called
complete flowers
– Flowers that do not are
called incomplete
• A monoecious plant has
both staminate and
carpellate flowers.
• If staminate and
carpellate flowers are on
separate plants, the plant
is dioecious
Holly-dioecious
10.1 Sexual Reproduction in Plants
• Life Cycle of Flowering Plants
– Flowering plants produce:
• Microspores
• Megaspores
10.1 Sexual Reproduction in Plants
• Life Cycle of Flowering Plants
– Microspores become mature male
gametophytes (sperm-bearing pollen grains)
– Megaspores become mature female
gametophytes (egg-bearing embryo sacs)
10.1 Sexual Reproduction in Plants
• Life Cycle of Flowering Plants
– During fertilization, one sperm nucleus unites
with the egg nucleus, producing a zygote.
– The other sperm unites with the polar nuclei,
forming a 3n endosperm cell.
10.1 Sexual Reproduction in Plants
• When cell walls form later, there are seven
cells, one of which is binucleate
• The female gametophyte, also called the
embryo sac, consists of these seven cells:
– one egg cell;
– two synergid cells;
– one central cell containing two polar nuclei
– three antipodal cells
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anther
Mature Seed
Development of the male
gametophyte:
In pollen sacs of the anther, a
microspore mother cell
undergoes meiosis to produce
4 microspores each.
seed coat
The ovule
develops into a
seed containing
the embryonic
sporophyte and
endosperm.
Development of the female
gametophyte:
In anovule within an ovary,
a megaspore mother cell
under goes meiosis to
produce 4 megaspores .
anther
mitosis
ovule
ovary
Pollen sac
embryo
endosperm (3n)
microspore
mother cell
Sporophyte
Seed
ovary
Ovule
megaspore
mother cell
diploid (2n)
MEIOSIS
MEIOSIS
DOUBLE FERTILIZATION
haploid (n)
ovule
wall
tube cell
Pollination
Microspores
During double
fertilization, one
sperm from the
male gametophyte
will fertilize the
egg; another
sperm will join with
polar nuclei to
produce the 3n
endosperm.
polarnuclei
egg
sperm
Development of
the sporophyte:
Pollination occurs;
a pollen grain
pollen
germinates and
tube
produces a pollen
tube.
generative cell
Megaspores
ovule
wall
Pollengrain
(malegametophyte)
sperm
antipodals
Mature male
gametophyte
tube
cell
nucleus
polarnuclei
egg cell
synergids
Embryosac
(mature female gametophyte)
(top): Courtesy Graham Kent; (bottom): © Ed Reschke
Microspores
develop into male
gametophytes
(pollen grains).
One megaspore
becomes the
embryosac
(female
gametophyte).
megaspore
3 megaspores
disintegrate
integument
micropyle
10.1 Sexual Reproduction in Plants
• Pollination
– The transfer of pollen from an anther to a
stigma
• Self-pollination (pollen is from the same plant)
• Cross-pollination (pollen is from a different plant)
10.1 Sexual Reproduction in Plants
• When a pollen grain lands on the stigma of
the same species, it germinates, forming a
pollen tube
• Pollen tube grows down to micropyle
• Double fertilization
– One sperm nucleus unites with egg forming
2n zygote
– Other sperm nucleus unites with polar nuclei
forming 3n endosperm cell
Pollinators
10.2 Growth and Development
• Development of the Eudicot Embryo
– The endosperm cell divides to produce
endosperm tissue
– The zygote divides into two cells
• One cell will become the embryo
– Embryonic cells near the suspensor become the root,
and those at the opposite end form the shoot
• The other cell will give rise to the suspensor
– The suspensor pushes the embryo into the endosperm
tissue
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endosperm
nucleus
zygote
endosperm
a.
b.
embryo
suspensor
basal cell
c.
cotyledons
appearing
shoot tip
epicotyl
bending
cotyledons
hypocotyl
bending
cotyledons
radicle
f.
root tip
e.
d.
10.2 Growth and Development
• Monocots Versus Eudicots
– Eudicots (two cotyledons)
• Cotyledons store nutrients that the embryo uses
– Monocots (one cotyledon)
• Cotyledon absorbs food molecules from the
endosperm and passes them to the embryo
10.2 Growth and Development
• Fruit
– Derived from an ovary and sometimes other
flower parts
– As a fruit develops, the ovary wall thickens to
become the pericarp
• May have up to three layers
10.2 Growth and Development
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• Types of fruit
seed covered
by pericarp
– Simple - derived from a
simple ovary of a single
carpel or from a
compound ovary of
several fused carpels
•
•
•
•
wing
a.
© James Mauseth
Legumes
Dry fruits
Fleshy fruits
Accessory fruits
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b.
flesh is from
receptacle
© Edward S. Ross
one fruit
10.2 Growth and Development
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one fruit
• Fruit Types
– Compound fruits
develop from
several individual
ovaries.
fruits from ovaries
of one flower
c.
© Runk/Schoenberger/Grant Heilman Photography
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Aggregate fruits
• Multiple fruits
fruits from ovaries
of many flowers
one fruit
d.
© Joe Solem/Riser/Getty Images
10.2 Growth and Development
• Dispersal of Seeds
– Seeds may have hooks or spines that attach
to fur or clothing
– Seeds may pass through the digestive tract of
animals
– Seeds may be gathered and buried by
animals
– Seeds may be carried by wind or water
10.2 Growth and Development
• Germination of Seeds
– Some types of seeds remain dormant until
conditions are favorable for growth
•
•
•
•
Temperature
Moisture
Regulatory Factors (stimulatory and inhibitory)
Mechanical Action (examples: water or fire)
Doomsday vault seed collection
Doomsday vault seed collection
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plumule
(epicotyl
with leaves)
hypocotyl
radicle
seed coat
cotyledon
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cotyledons (two)
epicotyl
withered
cotyledons
cotyledons (two)
first true leaves
(primary leaves)
hypocotyl
seed coat
hypocotyl
secondary
root
primary root
primary root
© BJ Miller/Biological Photo Service
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epicotyl
plumule
(epicotyl
with leaves)
hypocotyl
radicle
withered
cotyledons
cotyledons (two)
seed coat
cotyledon
first true leaves
(primary leaves)
a. Seed structure
hypocotyl
seed coat
hypocotyl
secondary
root
primary root
primary root
b. Germination and growth
© BJ Miller/Biological Photo Service
• Eudicot Versus Monocot Germination
– Eudicots – 2 cotyledons
• Cotyledons shrivel and degrade
• Epicotyl produces immature leaves and is called a plumule
• Young shoot is hook shaped as it emerges through the soil
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pericarp
endosperm
cotyledon
coleoptile
plumule
radicle
coleorhiza
a. Cornkernel
coleorhiza
primary root
coleoptile
© James Mauseth
first leaf
adventitious root
coleoptile
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true leaf
first leaf
coleoptile
radicle
adventitious root
coleoptile
coleorhiza
primary root
b. Germination and growth
prop root
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pericarp
endosperm
cotyledon
true leaf
coleoptile
plumule
radicle
coleorhiza
a. Cornkernel
coleorhiza
primary root
first leaf
adventitious root
coleoptile
radicle
coleoptile
prop root
coleorhiza
primary root
b. Germination and growth
b(left): © James Mauseth; b(right): © Barry L. Runk/Grant Heilman Photography
– Monocots – 1 cotyledon
• Cotyledon does not have a storage function
• Plumule and radicle are protected by coleoptile and the
coleorhiza
• Plumule and radicle burst through the sheaths when
germination occurs