Download The correct answer is d

1. Based on the finding from the embryonic flower mutant of Arabadopsis and use
of Arabadopsis for expression of the LEAFY gene, it has been show that—
a. flowering is entirely controlled by external cues
b. genes expressed later in plant development signal flowering
c. gene expression early in development suppresses flowering
d. b and c
The correct answer is d—
A. Answer a is incorrect. Flowering is often controlled by both internal and external
signals.
The correct answer is d—
B. Answer b is incorrect. This is not the only correct answer. Expression of the
LEAFY gene does promote flowering.
The correct answer is d—
C. Answer c is incorrect. This is not the only correct answer.Some genes are turned
on to inhibit flowering in young plants.
The correct answer is d—b and c
D. Answer d is correct. Answers b and c are both correct.
2. Your roommate is taking biology with you this semester and thinks he
understands short- and long-day plants. He purchases one plant of each type and
decides to see the difference himself by first trying to cause the short-day plant to
flower. He places both plants under the same conditions and exposes each to a
regimen of 10-hr days, expecting that the short-day plant will flower, and the
long-day plant will not. You play a trick on your roommate and reverse the
outcome. Specifically, what did you have to do?
a. Lengthen the time each is exposed to light
b. Shorten the time each is exposed to light
c. Quickly expose the plants to light during the middle of the night
d. None of the above
The correct answer is c—
A. Answer a is incorrect. Day length really has nothing to do with it, whereas night
length does.
The correct answer is c—
B. Answer b is incorrect. See the same reason as a.
The correct answer is c—Quickly expose the plants to light during the middle of the night
C. Answer c is correct. Short-day plants are really long-night plants and long-day
plants are really short-night plants. If you interrupt the period of dark with light,
you turn it into a short night, rather than a long night. This triggers flowering in
the long-day (short-night) plant and inhibits flowering in the short-day (long-
night) plant.
The correct answer is c—
D. Answer d is incorrect. Answer c is correct.
3. Which of the following does NOT serve as a cue for initiation of flowering?
a. Circadian cycle
b. Photoperiod
c. Gibberellin levels
d. Temperature
The correct answer is a—Circadian cycle
A. Answer a is correct. The circadian rhythm, in-and-of-itself, does not act as a cue
for flowering. It does interact with photoperiod.
The correct answer is a—
B. Answer b is true. Photoperiod can serve as an important cue.
The correct answer is a—
C. Answer c is true. Increased gibberellin levels can cue flowering.
The correct answer is a—
D. Answer d is true. Temperature serves as a flowering cue.
4. Which of the following would likely prevent flowering in a plant like tobacco
(Nicotiana tobacum) that follows the autonomous pathway?
a. removal of the lower leaves
b. removal of the apical meristem
c. continual upward-moving formation of adventitious roots on the stem
d. none of the above because the autonomous pathway sets a predetermined
time when flowering occurs
The correct answer is c—
A. Answer a is incorrect. Removal of the lower leaves does not affect the
autonomous pathway.
The correct answer is c—
B. Answer b is incorrect. The stem will grow back and flowering will occur.
The correct answer is c—continual upward-moving formation of adventitious roots on
the stem
C. Answer c is correct. The plant is essentially using the number of stem nodes as the
trigger. If you “trick” the plant into thinking it has fewer stem nodes by
functionally converting the stem into root, the plant will continue adding nodes
before it flowers.
The correct answer is c—
D. Answer d is incorrect. Plants like tobacco do count the number of nodes formed
before flowering.
5. Cryptochrome is responsible for—
a. blue-light-regulated responses
b. phototropisms
c. photoperiodic responses
d. a and c
The correct answer is d—
A. Answer a is incorrect. It is not the only correct response.
The correct answer is d—
B. Answer b is incorrect. Cryptochrome is not responsible for directed movements
through phototropisms.
The correct answer is d—
C. Answer c is incorrect. It is not the only correct response. Cryptochrome has a role
in photoperiodic responses.
The correct answer is d—a and c
D. Answer d is correct. Answers a and c are correct.
6. In Iowa, a company called Team Corn works to ensure that fields of seed corn
outcross so that hybrid vigor can be maintained. They do this by removing the
staminate (that is, pollen-producing) flowers from the corn plants. In an attempt to
put Team Corn out of business, you would like to develop genetically engineered
corn plants that—
a. contain Z genes to prevent germination of pollen on the stigmatic surface
b. contain S genes to stop pollen tube growth during self-fertilization
c. express B-type homeotic genes throughout developing flowers
d. express A-type homeotic genes throughout the developing flowers
The correct answer is b—
A. Answer a is incorrect. There are no Z genes in plants.
The correct answer is b—contain Z genes to stop pollen tube growth during selffertilization
B. Answer b is correct. S genes are the genes that allow plants to recognize selfpollen.
The correct answer is b—
C. Answer c is incorrect. Expressing the B-type homeotic gene throughout the
developing flower would lead to a duplication of petals and stamens, but would
not affect self-incompatibility.
The correct answer is b—
D. Answer d is incorrect. Expressing the A-type homeotic gene throughout the
developing flower would lead to a duplication of carpas and stamens, but would
not affect self-incompatibility.
7. Monoecious plants such as corn have either staminate or carpelate flowers.
Knowing what you do about the molecular mechanisms of floral development,
which of the following might explain the development of single-sex flowers?
a. Expression of B-type genes in the presumptive carpel whorl will generate
staminate flowers.
b. Loss of A-type genes in the presumptive petal whorl will allow C-type and
B-type genes to produce stamens instead of petals in that whorl.
c. Restricting B-type gene expression to the presumptive petal whorl will
generate carpelate flowers.
d. All of these are correct.
The correct answer is d—
A. Answer a is incorrect. Although expressing B-type genes in presumptive carpels
will transform them into stamens resulting in a staminate (or pistillate) flower,
this is not the only answer.
The correct answer is d—
B. Answer b is incorrect. Although expressing only B- and C-type genes in
presumptive petals will lead to a duplication of stamens, this is not the only
answer. This would result in flowers with two whorls of stamens and no petals.
The correct answer is d—
C. Answer c is incorrect. Although restricting B-type gene expression to presumptive
petals will lead to a duplication of carpels and a loss of stamens, thereby
producing a carpelate flower, this is not the only answer.
The correct answer is d—All of these are correct.
D. Answer d is correct. All of these are correct: Expression of B-type genes in
presumptive carpels will generate staminate flowers, expression of A-type genes
in presumptive stamens will generate carpelate flowers, and restricting B-type
gene expression to presumptive petals will generate carpelate flowers.
8. You have been asked to collect plant sperm for a new plant-breeding program
involving in vitro fertilization. Which of the following tissues would be a good
source of sperm?
a. Anthers
b. Ovaries
c. Stigma
d. Spores
The correct answer is a—Anthers
A. Answer a is correct. This is correct if the anthers have produced pollen. Pollen is
the male gametophyte that divides and produces sperm cells. You can collect
pollen from mature anthers.
The correct answer is a—
B. Answer b is incorrect. Eggs form within the ovaries, not sperm.
The correct answer is a—
C. Answer c is incorrect. Although the stigma might contain some pollen if
pollination has taken place, the anthers would be a much better source.
The correct answer is a—
D. Answer d is incorrect. Spores are the haploid cells that will give rise to the
gamete-producing generation of a plant (gametophyte).
9. If you wanted to create a super tobacco plant to increase the number of leaves per
acre on a tobacco farm, which of the following strategies would potentially work?
a. Suppress more root growth in the plants.
b. Decrease expression of the LEAFY gene in the shoot apical meristem.
c. Harvest lower leaves as the plant is growing so that flowering is delayed.
d. Remove flowers so that the plant will produce more vegetative internodes
than normal.
The correct answer is b—
A. Answer a is incorrect. Tobacco roots produce an inhibitor of flowering; this is
partly how tobacco regulates the number of internodes required before flowering
occurs. Suppressing root growth will accelerate flowering and reduce the amount
of vegetative growth.
The correct answer is b—Decrease expression of the LEAFY gene in the shoot apical
meristem.
B. Answer b is correct. Expression of the LEAFY gene is required to initiate
flowering. By decreasing LEAFY gene expression, the vegetative phase of growth
will be extended and more leaves will be produced.
The correct answer is b—
C. Answer c is incorrect. The lower leaves may produce a floral inhibitor necessary
to delay flowering and extend the production of leaves.
The correct answer is b—
D. Answer d is incorrect. After the tobacco plant has flowered it will stop growing.
The shoot tip is consumed in the production of a terminal flower.
10. One of the most notable differences between gamete formation in most animals
and gamete formation in plants is that—
a. plants produce gametes in somatic tissue, whereas animals produce
gametes in germ tissue
b. plants produce gametes by mitosis, whereas animals produce gametes by
meiosis
c. plants produce only one of each gamete, but animals produce many
gametes
d. plants produce gametes that are diploid, but animals produce gametes that
are haploid
The correct answer is b—
A. Answer a is incorrect. Plants produce gametes in gametophytic tissue, and animals
produce gametes in germ tissue.
The correct answer is b—plants produce gametes by mitosis, whereas animals produce
gametes by meiosis
B. Answer b is correct. Plants do produce gametes by mitosis in gametophytic tissue,
but animals produce gametes by meiosis in the germ line.
The correct answer is b—
C. Answer c is incorrect. Plants and animals can produce large numbers of gametes.
The correct answer is b—
D. Answer d is incorrect. Both plant and animal gametes are haploid; this is critical
for maintaining the ploidy of successive generations.
11. If you were to discover a flower that was small, white, and heavily scented, its
most likely pollinator would be—
a. bees
b. birds
c. humans
d. moths
The correct answer is d—
A. Answer a is incorrect. Bees are usually attracted by relatively large flowers and
prefer yellow and blue pigmentation.
The correct answer is d—
B. Answer b is incorrect. Birds are usually attracted by the color red, not white.
The correct answer is d—
C. Answer c is incorrect. We are usually attracted by large, brightly colored flowers
with nice scents.
The correct answer is d—moths
D. Answer d is correct. Moths are usually drawn to small, colorless flowers with
strong scents; this helps them find the flowers at night when most moths are
active.
12. Under which of the following conditions would pollen from an S2S5 plant
successfully pollinate an S1S5 flower?
a. Using pollen from a carpelate flower to fertilize a staminate flower would
be successful.
b. If the plants used gametophytic self-incompatibility, half of the pollen
would be successful.
c. If the plants used sporophytic self-incompatibility, half of the pollen
would be successful.
d. Pollen from an S2S5 plant can never pollinate an S1S5 flower.
The correct answer is b—
A. Answer a is incorrect. Pollen comes from staminate flowers and fertilizes
carpelate flowers.
The correct answer is b—If the plants used gamtophytic self-incompatibility, half of the
pollen would be successful.
B. Answer b is correct. In gametophytic self-incompatibility, the S2 pollen would
successfully pollinate the S1S5 flower, but the S5 pollen would not.
The correct answer is b—
C. Answer c is incorrect. None of the pollen from an S2S5 plant would germinate on
an S1S5 stigma.
The correct answer is b—
D. Answer d is incorrect. S2S5 pollen can pollinate S1S5 flowers if they use
gametophytic self-incompatibility.
Challenge Questions
1. We often have the impression that plants lack the ability to move around in the
environment. This, however, is far from the truth. Discuss the variety of ways
that plants successfully move throughout the environment.
Answer—Plants use animals to move across large distances. The flowering plants are
particularly good at dispersing their offspring. Animals carry fruit and seed over long
distances in their mouths, on their bodies, or in their guts. Pollen can be carried to another
plant of the same species by wind or an animal pollinator, allowing plants to mate even
though they are quite far apart. Unlike most animals, however, the plant does not have its
own organs for locomotion and must piggyback on an animal or the wind to get around in
the environment.
2. Identify the pros and cons of plants that are wind-pollinated versus those that are
animal-pollinated.
Answer—Plants that are wind-pollinated can save energy by not having to produce
attractants, such as nectar or colorful sepals, for pollinators. However, in order to have
effective pollination, they must produce a lot of pollen. Distances for successful
pollination are limited. Plants with animal-pollinated flowers have the luxury of relying
heavily on the directed dispersal of pollen from one plant to another by animals, such as
bees, butterflies, and birds. This allows them to produce less pollen and still have
successful pollination. However, energy must be spent on nectar and colorful flowers.
One potential problem that exists with plants that have animal-dispersed pollen is that if a
specific pollinator becomes rare or extinct, effective pollination may be reduced or
stopped completely. Furthermore, structural changes that might occur in either the flower
or pollinator could also affect pollination success. These would not be problematic for
wind-pollinated species.
3. Compare the ecological advantages and disadvantages of plants that reproduce
sexually, those that reproduce via apomixis, and those that have vegetative
reproduction.
Answer—Plants that reproduce sexually have the advantage of genetic diversity, thus
allowing them to potentially inhabit a variety of habitats and cope with environmental
changes as a population. Production of seed by sexual reproduction or apomixis will also
likely lead to better dispersal. Plants that reproduce via apomixis produce seeds that are
genetically identical to the parent. With this, they get the advantage of dispersal, but
would not be producing any genetic diversity. This serves well for unchanging habitats,
but these species may not cope well with environmental changes. Plants that demonstrate
vegetative reproduction rarely have good dispersal and they produce little genetic
variability. However, if these species exist in relatively unchanging environments, these
are perfect means for successful reproduction.