Chapter 38: Reproduction in Flowering Plants
CHAPTER 38
Reproduction in
Flowering Plants
Chapter 38: Reproduction in Flowering Plants
Chapter 38: Reproduction in
Flowering Plants
Many Ways to Reproduce
Sexual Reproduction
The Transition to the Flowering State
Chapter 38: Reproduction in Flowering Plants
Chapter 38: Reproduction in
Flowering Plants
Photoperiodic Control of Flowering
Vernalization and Flowering
Asexual Reproduction
Chapter 38: Reproduction in Flowering Plants
Many Ways to Reproduce
• Almost all flowering plants reproduce
sexually, and many also reproduce
asexually.
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Chapter 38: Reproduction in Flowering Plants
Many Ways to Reproduce
• Both sexual and asexual reproduction are
important in agriculture.
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Chapter 38: Reproduction in Flowering Plants
Sexual Reproduction
• Sexual reproduction promotes genetic
diversity in a population, which may give the
population an advantage under changing
environmental conditions.
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Chapter 38: Reproduction in Flowering Plants
Sexual Reproduction
• The flower is an angiosperm’s device for
sexual reproduction.
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Chapter 38: Reproduction in Flowering Plants
Sexual Reproduction
• Flowering plants have microscopic
gametophytes that develop in flowers of the
sporophytes.
• The megagametophyte is the embryo sac,
which typically contains eight nuclei in seven
cells.
• The microgametophyte is the pollen grain,
which delivers two sperm cells to the
megagametophyte via a long pollen tube.
Review Figure 38.1
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Chapter 38: Reproduction in Flowering Plants
Figure
38.1
Figure 38.1
figure 38-01.jpg
Chapter 38: Reproduction in Flowering Plants
Sexual Reproduction
• Pollination enables fertilization in the
absence of liquid water.
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Chapter 38: Reproduction in Flowering Plants
Sexual Reproduction
• In self-incompatible species, the stigma
rejects pollen from the same plant.
Review Figure 38.4
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Chapter 38: Reproduction in Flowering Plants
Figure 38.4
Figure 38.4
figure 38-04.jpg
Chapter 38: Reproduction in Flowering Plants
Sexual Reproduction
• Angiosperms perform double fertilization:
• One sperm nucleus fertilizes the egg,
forming a zygote
• The other unites with the two polar nuclei to
form a triploid endosperm nucleus. Review
Figure 38.6
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Chapter 38: Reproduction in Flowering Plants
figure 38-06.jpg
Figure
38.6
Figure 38.6
Chapter 38: Reproduction in Flowering Plants
Sexual Reproduction
• The zygote develops into an embryo,
remaining quiescent in the seed until
conditions are right for germination.
• The endosperm is the nutritive reserve upon
which the embryo depends at germination.
Review Figures 38.7, 38.8
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Chapter 38: Reproduction in Flowering Plants
Figure 38.7
Figure 38.7
figure 38-07.jpg
Chapter 38: Reproduction in Flowering Plants
Figure
38.8
Figure 38.8
figure 38-08.jpg
Chapter 38: Reproduction in Flowering Plants
Sexual Reproduction
• Flowers develop into seed-containing fruits,
which often play important roles in the
dispersal of the species.
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Chapter 38: Reproduction in Flowering Plants
The Transition to the
Flowering State
• For a vegetatively growing plant to flower,
an apical meristem in the shoot system
must become an inflorescence meristem,
which gives rise to bracts and more
meristems.
• These new meristems may become floral
meristems or additional inflorescence
meristems. Review Figure 38.10
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Chapter 38: Reproduction in Flowering Plants
figure 38-10.jpg
Figure
38.10
Figure 38.10
Chapter 38: Reproduction in Flowering Plants
The Transition to the
Flowering State
• Flowering results from a cascade of gene
expression.
• Organ identity genes are expressed in floral
meristems that give rise to sepals, petals,
stamens, and carpels.
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Chapter 38: Reproduction in Flowering Plants
Photoperiodic Control of
Flowering
• Photoperiodic plants regulate flowering by
measuring length of light and dark periods.
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Chapter 38: Reproduction in Flowering Plants
Photoperiodic Control of
Flowering
• Short-day plants flower when days are
shorter than a species-specific critical day
length; long-day plants flower when days
are longer than a critical day length.
Review Figure 38.11
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Chapter 38: Reproduction in Flowering Plants
Figure
38.11
Figure 38.11
figure 38-11.jpg
Chapter 38: Reproduction in Flowering Plants
Photoperiodic Control of
Flowering
• Some angiosperms have more complex
photoperiodic requirements than short-day
or long-day plants, but most are dayneutral.
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Chapter 38: Reproduction in Flowering Plants
Photoperiodic Control of
Flowering
• The length of the night is what actually
determines whether a photoperiodic plant
will flower. Review Figure 38.12
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Chapter 38: Reproduction in Flowering Plants
Figure 38.12
Figure 38.12
figure 38-12.jpg
Chapter 38: Reproduction in Flowering Plants
Photoperiodic Control of
Flowering
• Interruption of the nightly dark period by a
brief exposure to light undoes the effect of
a long night. Review Figure 38.13
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Chapter 38: Reproduction in Flowering Plants
Figure 38.13 –
Part 1
Figure 38.13 – Part 1
figure 38-13a.jpg
Chapter 38: Reproduction in Flowering Plants
Figure 38.13
– Part 2
Figure 38.13 – Part 2
figure 38-13b.jpg
Chapter 38: Reproduction in Flowering Plants
Photoperiodic Control of
Flowering
• The mechanism of photoperiodic control
involves a biological clock and
phytochromes.
Review Figures 38.14, 38.15
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Chapter 38: Reproduction in Flowering Plants
Figure
38.14
Figure 38.14
figure 38-14.jpg
Chapter 38: Reproduction in Flowering Plants
Figure
38.15
Figure 38.15
figure 38-15.jpg
Chapter 38: Reproduction in Flowering Plants
Photoperiodic Control of
Flowering
• Evidence suggests there is a flowering
hormone, called florigen, but it has yet to
be isolated from any plant.
Review Figure 38.16
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Chapter 38: Reproduction in Flowering Plants
Figure
38.16 –
Part 1
Figure 38.16 – Part 1
figure 38-16a.jpg
Chapter 38: Reproduction in Flowering Plants
Figure
38.16 –
Part 2
Figure 38.16 – Part 2
figure 38-16b.jpg
Chapter 38: Reproduction in Flowering Plants
Vernalization and Flowering
• In some plant species, exposure to low
temperatures—vernalization—is required for
flowering.
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Chapter 38: Reproduction in Flowering Plants
Asexual Reproduction
• Asexual reproduction allows rapid
multiplication of organisms well suited to
their environment.
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Chapter 38: Reproduction in Flowering Plants
Asexual Reproduction
• Vegetative reproduction involves
modification of a vegetative organ for
reproduction.
Stolons (horizontal stems w/roots)
 Rhizomes(underground hor. stems)
 Bulbs – lilies, onions
 Corms - disc-like underground stems
 Suckers – shoots produced by roots

Chapter 38: Reproduction in Flowering Plants
Asexual Reproduction
• Some plant species produce seeds asexually
by apomixis (female gametophyte produces
seeds without pollen fertilization).
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Chapter 38: Reproduction in Flowering Plants
Asexual Reproduction
• Agriculturalists use natural and artificial
techniques of asexual reproduction to
reproduce desirable plants.
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Chapter 38: Reproduction in Flowering Plants
Asexual Reproduction
• Horticulturists often graft different plants
together to take advantage of favorable
properties of both stock(root bearing) and
scion(upper graft).
Review Figure 38.18
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Chapter 38: Reproduction in Flowering Plants
Figure
38.18
Figure 38.18
figure 38-18.jpg
Chapter 38: Reproduction in Flowering Plants
Asexual Reproduction
• Tissue culture techniques, based on the
totipotency of many plant cells, are used to
propagate plants asexually, produce virusfree clones of crop plants, and manipulate
plants by recombinant DNA technology.
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