Transcript Chapter 27 Opener Figure 21.1 The Evolution of Plants Figure 21.1 The Evolution of Plants (Part 2)

Chapter 27 Opener
Figure 21.1 The Evolution of Plants
Figure 21.1 The Evolution of Plants (Part 2)
Figure 21.1 The Evolution of Plants (Part 1)
Figure 21.4 Alternation of Generations in Land Plants
Figure 21.4 Alternation of Generations in Land Plants
In-Text Art, Ch. 27, p. 557
Figure 27.1 Perfect and Imperfect Flowers
Figure 27.1 Perfect and Imperfect Flowers (Part 1)
Figure 27.1 Perfect and Imperfect Flowers (Part 2)
Figure 27.1 Perfect and Imperfect Flowers (Part 3)
Concept 27.1 Most Angiosperms Reproduce Sexually
Angiosperm gametophytes are microscopic.
Female (megagametophyte), or embryo sac arises from
a megaspore.
Consists of 7 cells:
• 1 egg cell
• 2 synergids (attract pollen tube and receive
sperm)
• 3 antipodal cells degenerate
• 1 central cell with 2 polar nuclei
Concept 27.1 Most Angiosperms Reproduce Sexually
Male (microgametophytes), or pollen grains, arise from
microspores.
Consist of 2 cells:
Generative cell divides by mitosis to form two sperm
cells that participate in fertilization.
Tube cell forms pollen tube that delivers the sperm to
embryo sac.
Figure 27.2 Sexual Reproduction in Angiosperms
Figure 27.3 Self-incompatibility
Figure 27.4 Double Fertilization
Figure 27.4 Double Fertilization
Figure 27.5 Angiosperm Fruits
Figure 27.5 Angiosperm Fruits (Part 1)
Figure 27.5 Angiosperm Fruits (Part 2)
Figure 27.5 Angiosperm Fruits (Part 3)
In-Text Art, Ch. 27, p. 561 (1)
In-Text Art, Ch. 27, p. 561 (2)
Concept 27.1 Most Angiosperms Reproduce Sexually
With a partner, discuss the differences between sexual
reproduction in angiosperms and animals.
Consider, for example, the products of mitosis and meiosis
and the alternation of haploid and diploid generations.
Concept 27.1 Most Angiosperms Reproduce Sexually
Draw a diagram of a flower and label all of the following:
Anther
Filament
Ovule
Sepal
Stigma
Carpel
Ovary
Petal
Stamen
Style
[Note: If a real flower is available, see if you can identify all of these
parts on the real flower, too.]
Compare your drawing with your neighbors and discuss:
1. Did you draw a perfect or an imperfect flower?
2. Where is the male gametophyte?
3. Where is the female gametophyte?
4. Where is the sporophyte?
5. Which part will become the seed?
6. Which will become the rest of the fruit?
Concept 27.1 Most Angiosperms Reproduce Sexually
Which of the following correctly describes an imperfect
flower?
a. Has male and female sex organs
b. Has both stamens and carpels
c. Has only male or only female sex organs
d. I don’t know.
Concept 27.1 Most Angiosperms Reproduce Sexually
Without looking at your notes, answer the following
questions.
1. Is self-fertilization possible in dioecious plants? Why
or why not?
2. How is self-fertilization prevented in monoecious
plants?
When you are finished, discuss your answers with a
partner.
Concept 27.1 Most Angiosperms Reproduce Sexually
Draw a fruit and label the following:
• The seed with the embryo
• The ovary wall
Then answer the following questions:
1. What part of the flower are you eating when you bite
into an apple?
2. What are the two main functions of fruit?
Figure 27.6 The Transition to Flowering
Figure 27.6 The Transition to Flowering
Concept 27.2 Hormones and Signaling Determine the Transition
from the Vegetative to the Reproductive State
Genes that determine the transition to floral meristems
have been studied in Arabidopsis.
Meristem identity genes LEAFY and APETALA1 initiate
a cascade of gene expression.
Floral organ identity genes: homeotic genes; products
are transcription factors that determine whether cells
in the floral meristem will be sepals, petals, stamens,
or carpels.
Figure 27.6 The Transition to Flowering (Part 1)
Figure 27.6 The Transition to Flowering (Part 2)
Figure 27.6 The Transition to Flowering (Part 3)
Concept 27.2 Hormones and Signaling Determine the Transition
from the Vegetative to the Reproductive State
External cues that initiate gene expression for flowering:
1. Photoperiod (day length)—Some species flower only
when days reach a specific length.
• Short-day plants (SDPs) flower only when the day is
shorter than a critical maximum.
• Long-day plants (LDPs) flower only when the day is
longer than a critical minimum.
Concept 27.2 Hormones and Signaling Determine the Transition
from the Vegetative to the Reproductive State
Plants sense night length by measuring the ratio of Pfr to
Pr.
Day—more red light than far-red; by end of day most
phytochrome is Pfr.
At night Pfr is gradually converted back to Pr. The longer
the night, the more Pr there is at dawn.
A SDP flowers when ratio of Pfr to Pr is low at the end of
the night; a LDP flowers when this ratio is high.
Concept 27.2 Hormones and Signaling Determine the Transition
from the Vegetative to the Reproductive State
Phytochrome is located in the leaf.
The signal for flowering must be a diffusible chemical
that travels from the leaf to the shoot apical meristem.
The diffusible chemical is the protein florigen.
Figure 39.19 Structure of a phytochrome
Figure 39.20 Phytochrome: a molecular switching mechanism
Figure 27.7 Photoperiod and Flowering
Figure 27.7 Photoperiod and Flowering
Figure 27.8 Night Length and Flowering
Figure 27.8 Night Length and Flowering
Hormones and signaling determine the transition from the
vegetative to the flowering state
The experiments reported on in fig. 27.8 were repeated using a
long-day plant (LDP) that normally flowers with a 16-hour
photoperiod. The plant was subjected to the light regimes
listed in the table.
1. List the light regimes that should have resulted in flowering.
2. Predict the effect of adding a brief period of far-red light in
the middle of the dark period of each light regime.
3. Predict the effect of adding a brief period of red light in the
middle of the dark period of each light regime.
Apply the Concept, Ch. 27, p. 564
Figure 39.22 Photoperiodic control of flowering
Figure 27.9 The Flowering Signal Moves from Leaf to Bud
Figure 27.9 The Flowering Signal Moves from Leaf to Bud (Part 1)
Figure 27.9 The Flowering Signal Moves from Leaf to Bud (Part 2)
Figure 27.10 Molecular Biology of Flowering
Concept 27.2 Hormones and Signaling Determine the Transition
from the Vegetative to the Reproductive State
The genes involved in flowering:
FT (FLOWERING LOCUS T) codes for florigen.
CO (CONSTANS) codes for a transcription factor that
activates synthesis of FT; expressed in phloem
companion cells.
FD (FLOWERING LOCUS D) codes for a transcription
factor that binds to FT in the shoot apical meristem.
The complex activates promoters for meristem identity
genes, such as APETALA1.
Concept 27.2 Hormones and Signaling Determine the Transition
from the Vegetative to the Reproductive State
External cues that initiate gene expression for flowering:
2. Temperature
Some plants flower after a period of cold temperatures
(vernalization).
Cold temperatures inhibit synthesis of FLC protein, a
transcription factor that inhibits expression of FT and
FD.
Figure 27.10 Molecular Biology of Flowering
Figure 27.10 Molecular Biology of Flowering (Part 1)
Figure 27.10 Molecular Biology of Flowering (Part 2)
Figure 35.36 The ABC hypothesis for the functioning of organ identity genes in flower development
Concept 27.2 Hormones and Signaling Determine the Transition from the Vegetative to the
Reproductive State
With a partner, review the different types of meristems.
Then answer the following questions:
1. What do shoot apical meristems produce?
2. What do shoot apical meristems become?
3. What do inflorescence meristems produce?
4. What does a floral meristem become?
Concept 27.2 Hormones and Signaling Determine the Transition from the Vegetative to the
Reproductive State
What is the critical factor that induces flowering?
a. Day length
b. Night length
c. Age of plant
d. Red light exposure
Concept 27.3 Angiosperms Can Reproduce Asexually
Why is cloning a good reproductive method for some plant
species? That is, why might asexual reproduction be
adaptive?
Concept 27.3 Angiosperms Can Reproduce Asexually
What is it called when one of these two events occurs?
1. The megasporocyte in the ovule that is supposed to
undergo meiosis fails to do so, resulting in a diploid
egg cell, which then goes on to form an embryo and
seed.
2. Diploid cells from the integument surrounding the
embryo sac form a diploid embryo sac, which goes
on to form an embryo and seed.
Does seed and fruit development proceed?
What does the plant produce?
Concept 27.3 Angiosperms Can Reproduce Asexually
Which term does not belong with the others?
a. Vegetative reproduction
b. Cloning
c. Apomixis
d. Sexual reproduction
e. Asexual reproduction
Concept 27.3 Angiosperms Can Reproduce Asexually
Describe the importance and function of the vascular
cambium in the grafting process.
Figure 27.11 Vernalization
In-Text Art, Ch. 27, p. 568
Figure 27.12 Vegetative Reproduction
Figure 27.12 Vegetative Reproduction
Figure 27.12 Vegetative Reproduction (Part 1)
Figure 27.12 Vegetative Reproduction (Part 2)
Figure 27.12 Vegetative Reproduction (Part 3)
Figure 27.13 The Advantage of Asexual Reproduction by Apomixis
Figure 27.13 The Advantage of Asexual Reproduction by Apomixis
Figure 27.14 Grafting
Figure 27.14 Grafting
Figure 27.15 A Wild Relative of Poinsettia