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CAMPBELL
BIOLOGY
TENTH
EDITION
Reece • Urry • Cain • Wasserman • Minorsky • Jackson
39
Plant Responses to Internal
and External Signals
Clicker Questions by
Scott T. Meissner
© 2014 Pearson Education, Inc.
According to the acid growth hypothesis, what is the correct
sequence in which the following events leading to auxininduced cell elongation occur?
1. Cross-links between cellulose microfibrils and
polysaccharides of the cell wall are enzymatically
broken.
2. Increased turgor pressure of cell cytoplasm expands
the cell.
3. Proton pumps move H into the cell wall.
a) 1, 2, 3
d) 3, 2, 1
b) 1, 3, 2
e) 3, 1, 2
c) 2, 3, 1
© 2014 Pearson Education, Inc.
According to the acid growth hypothesis, what is the correct
sequence in which the following events leading to auxininduced cell elongation occur?
1. Cross-links between cellulose microfibrils and
polysaccharides of the cell wall are enzymatically
broken.
2. Increased turgor pressure of cell cytoplasm expands
the cell.
3. Proton pumps move H into the cell wall.
a) 1, 2, 3
d) 3, 2, 1
b) 1, 3, 2
e) 3, 1, 2
c) 2, 3, 1
© 2014 Pearson Education, Inc.
Which of these could explain auxin-induced cell elongation, as
pictured in the figure? (NOTE: The cell does NOT increase in
size in all dimensions.)
1. Proton pumps, homogeneously distributed in the plasma membrane,
are all equally active.
2. Active proton pumps are limited to the portion of the plasma membrane
that is parallel to the axis of elongation.
3. Expansins and/or cell wall–loosening enzymes are homogeneously
distributed outside of the plasma membrane.
4. Expansins and/or cell wall–loosening enzymes are limited to the
exterior of the cell on the side that is perpendicular to the axis of
elongation.
a) 1 only
d) 1 or 4
b) 2 only
e) 2 and 4
c) 1 or 3
© 2014 Pearson Education, Inc.
Which of these could explain auxin-induced cell elongation, as
pictured in the figure? (NOTE: The cell does NOT increase in
size in all dimensions.)
1. Proton pumps, homogeneously distributed in the plasma membrane,
are all equally active.
2. Active proton pumps are limited to the portion of the plasma membrane
that is parallel to the axis of elongation.
3. Expansins and/or cell wall–loosening enzymes are homogeneously
distributed outside of the plasma membrane.
4. Expansins and/or cell wall–loosening enzymes are limited to the
exterior of the cell on the side that is perpendicular to the axis of
elongation.
a) 1 only
d) 1 or 4
b) 2 only e) 2 and 4
c) 1 or 3
© 2014 Pearson Education, Inc.
Which of these is most directly involved in causing the
leaves of deciduous trees to fall in autumn?
a) cytokinins
b) gibberellins
c) abscisic acid
d) ethylene
e) brassinosteroids
© 2014 Pearson Education, Inc.
Which of these is most directly involved in causing the
leaves of deciduous trees to fall in autumn?
a) cytokinins
b) gibberellins
c) abscisic acid
d) ethylene
e) brassinosteroids
© 2014 Pearson Education, Inc.
A patch of soil contains ungerminated seeds. If this
patch gets covered by a newly laid concrete sidewalk,
then which of these phenomena will the seedlings
under the sidewalk exhibit if they germinate, and which
hormone accounts for this phenomenon?
a) triple response; ethylene
b) seed dormancy; abscisic acid
c) anti-aging effects; cytokines
d) anti-aging effects; abscisic acid
e) triple response; brassinosteroids
© 2014 Pearson Education, Inc.
A patch of soil contains ungerminated seeds. If this
patch gets covered by a newly laid concrete sidewalk,
then which of these phenomena will the seedlings
under the sidewalk exhibit if they germinate, and which
hormone accounts for this phenomenon?
a) triple response; ethylene
b) seed dormancy; abscisic acid
c) anti-aging effects; cytokines
d) anti-aging effects; abscisic acid
e) triple response; brassinosteroids
© 2014 Pearson Education, Inc.
Circadian rhythms, seasonal rhythms, and seedling
germination are most strongly influenced by a
molecular switching mechanism that involves a
phytochrome sensitive to both
a) violet light and ultraviolet light.
b) infrared radiation and red light.
c) red light and far-red light.
d) blue light and red light.
e) geomagnetism and cosmic radiation.
© 2014 Pearson Education, Inc.
Circadian rhythms, seasonal rhythms, and seedling
germination are most strongly influenced by a
molecular switching mechanism that involves a
phytochrome sensitive to both
a) violet light and ultraviolet light.
b) infrared radiation and red light.
c) red light and far-red light.
d) blue light and red light.
e) geomagnetism and cosmic radiation.
© 2014 Pearson Education, Inc.
If one experimentally wants to get a long-day (shortnight) plant to flower at a time when nights are longer
than the critical night length, the best way would be to
interrupt the plant’s
a) days with a few minutes of complete darkness
during its exposure to light.
b) nights with a few minutes of exposure to blue light.
c) nights with a few minutes of exposure to far-red
light.
d) nights with a few minutes of exposure to red
light.
e) nights with a few minutes of exposure to any color
of light.
© 2014 Pearson Education, Inc.
If one experimentally wants to get a long-day (shortnight) plant to flower at a time when nights are longer
than the critical night length, the best way would be to
interrupt the plant’s
a) days with a few minutes of complete darkness
during its exposure to light.
b) nights with a few minutes of exposure to blue light.
c) nights with a few minutes of exposure to far-red
light.
d) nights with a few minutes of exposure to red
light.
e) nights with a few minutes of exposure to any color
of light.
© 2014 Pearson Education, Inc.
In animals, signaling chemicals may move from cell to
cell via gap junctions. In plants, which structures are
analogous to gap junctions, and which plant hormone
moves from leaves to shoot apical meristems through
these structures?
a) nuclear pores; florigens
b) tight junctions; cytokinins
c) tight junctions; auxins
d) plasmodesmata; auxins
e) plasmodesmata; florigens
© 2014 Pearson Education, Inc.
In animals, signaling chemicals may move from cell to
cell via gap junctions. In plants, which structures are
analogous to gap junctions, and which plant hormone
moves from leaves to shoot apical meristems through
these structures?
a) nuclear pores; florigens
b) tight junctions; cytokinins
c) tight junctions; auxins
d) plasmodesmata; auxins
e) plasmodesmata; florigens
© 2014 Pearson Education, Inc.
For plants to sense gravity in their roots, one model
proposes that they use the distribution of what
organelle? What type of gravitropism would roots
typically display as a result?
a) otoliths; positive gravitropism
b) statoliths; positive gravitropism
c) statoliths; negative gravitropism
d) statocysts; negative gravitropism
e) statocysts; positive gravitropism
© 2014 Pearson Education, Inc.
For plants to sense gravity in their roots, one model
proposes that they use the distribution of what
organelle? What type of gravitropism would roots
typically display as a result?
a) otoliths; positive gravitropism
b) statoliths; positive gravitropism
c) statoliths; negative gravitropism
d) statocysts; negative gravitropism
e) statocysts; positive gravitropism
© 2014 Pearson Education, Inc.
In response to temperature extremes, plants may
synthesize either heat-shock proteins or antifreeze
proteins, proteins that help protect against which
dangers, respectively?
a) protein denaturation, ice crystal formation
b) wilting, inability to synthesize hormones
c) permanent closure of stomata, evapotranspiration
d) leaf abscission, protein denaturation
e) evapotranspiration, inability to perform motor
activities
© 2014 Pearson Education, Inc.
In response to temperature extremes, plants may
synthesize either heat-shock proteins or antifreeze
proteins, proteins that help protect against which
dangers, respectively?
a) protein denaturation, ice crystal formation
b) wilting, inability to synthesize hormones
c) permanent closure of stomata, evapotranspiration
d) leaf abscission, protein denaturation
e) evapotranspiration, inability to perform motor
activities
© 2014 Pearson Education, Inc.
Plant cells can do all of the following in response to
attack by a pathogen except
a) kill themselves.
b) synthesize chemicals that inhibit the pathogen.
c) limit the spread of the pathogen to other cells.
d) secrete chemicals that signal the presence of
pathogens to other parts of the plant.
e) create antibodies against specific items found
in the pathogen.
© 2014 Pearson Education, Inc.
Plant cells can do all of the following in response to
attack by a pathogen except
a) kill themselves.
b) synthesize chemicals that inhibit the pathogen.
c) limit the spread of the pathogen to other cells.
d) secrete chemicals that signal the presence of
pathogens to other parts of the plant.
e) create antibodies against specific items found
in the pathogen.
© 2014 Pearson Education, Inc.
What is the correct sequence in which these events of
systemic acquired resistance occur?
1. Phloem transports chemical signal to plant parts
distant from the site of attack.
2. Damaged tissues secrete methylsalicylic acid.
3. Salicylic acid induces production of PR proteins
4. Methylsalicylic acid is converted to salicylic acid in
healthy cells.
a) 1, 2, 4, 3
d) 2, 1, 4, 3
b) 1, 3, 4, 2
e) 2, 4, 3, 1
c) 2, 4, 1, 3
© 2014 Pearson Education, Inc.
What is the correct sequence in which these events of
systemic acquired resistance occur?
1. Phloem transports chemical signal to plant parts
distant from the site of attack.
2. Damaged tissues secrete methylsalicylic acid.
3. Salicylic acid induces production of PR proteins
4. Methylsalicylic acid is converted to salicylic acid in
healthy cells.
a) 1, 2, 4, 3
d) 2, 1, 4, 3
b) 1, 3, 4, 2
e) 2, 4, 3, 1
c) 2, 4, 1, 3
© 2014 Pearson Education, Inc.
Which of the following choices is a growth response,
not a behavioral response?
a) opening of the leaf’s stomatal pores during the day
when sufficient water is available
b) leaflet folding by Mimosa pudica upon being touched
c) elongation of a cell in the root cortex upon
auxin-induced cell wall acidification
d) “sleep” movement of plant leaves at night to align
them vertically
e) closing of stomatal pores when the guard cells
detect a certain concentration of abscisic acid
© 2014 Pearson Education, Inc.
Which of the following choices is a growth response,
not a behavioral response?
a) opening of the leaf’s stomatal pores during the day
when sufficient water is available
b) leaflet folding by Mimosa pudica upon being touched
c) elongation of a cell in the root cortex upon
auxin-induced cell wall acidification
d) “sleep” movement of plant leaves at night to align
them vertically
e) closing of stomatal pores when the guard cells
detect a certain concentration of abscisic acid
© 2014 Pearson Education, Inc.
The de-etiolation response (see figure) is a growth
response, and not a behavioral response, because
a) it involves the formation of new permanent
structures and molecules.
b) the response is done upon the detection of light.
c) there is the involvement of complex transduction
mechanisms.
d) two sets of protein
kinases are involved
in transduction.
e) the concentration
of cyclic GMP
initially rises.
© 2014 Pearson Education, Inc.
The de-etiolation response (see figure) is a growth
response, and not a behavioral response, because
a) it involves the formation of new permanent
structures and molecules.
b) the response is done upon the detection of light.
c) there is the involvement of complex transduction
mechanisms.
d) two sets of protein
kinases are involved
in transduction.
e) the concentration
of cyclic GMP
initially rises.
© 2014 Pearson Education, Inc.
Many plant hormones influence the pattern of plant
growth. This makes them most analogous to which of
the following in animals?
a) passage of action potentials between various parts of the
body of the organism that affect local activities
b) uses of hormones in preparing for “flight-or-flight”
behavioral responses in many animals
c) the use of hormones in negative feedback systems to
achieve homeostasis in adult organisms
d) items secreted in animal embryos used to help
organize their development
e) various receptors used to detect external signals to
which the organism responds
© 2014 Pearson Education, Inc.
Many plant hormones influence the pattern of plant
growth. This makes them most analogous to which of
the following in animals?
a) passage of action potentials between various parts of the
body of the organism that affect local activities
b) uses of hormones in preparing for “flight-or-flight”
behavioral responses in many animals
c) the use of hormones in negative feedback systems to
achieve homeostasis in adult organisms
d) items secreted in animal embryos used to help
organize their development
e) various receptors used to detect external signals to
which the organism responds
© 2014 Pearson Education, Inc.
Which is a common means by which plant hormones
manage to show up at certain sites throughout the
plant’s body?
a) Specific proteins bind each hormone and act to deliver
it to the desired location.
b) Many are actively moved, by cytoplasmic streaming
or phloem bulk flow, along the symplastic pathways
of the plant.
c) They move through the use of diffusion down each
hormone’s extracellular concentration gradient.
d) The detection of signals induces the local production of
the needed plant hormones at each location.
e) Vesicles loaded with each type of hormone are often
placed into the xylem for rapid passage to the leaves.
© 2014 Pearson Education, Inc.
Which is a common means by which plant hormones
manage to show up at certain sites throughout the
plant’s body?
a) Specific proteins bind each hormone and act to deliver
it to the desired location.
b) Many are actively moved, by cytoplasmic streaming
or phloem bulk flow, along the symplastic pathways
of the plant.
c) They move through the use of diffusion down each
hormone’s extracellular concentration gradient.
d) The detection of signals induces the local production of
the needed plant hormones at each location.
e) Vesicles loaded with each type of hormone are often
placed into the xylem for rapid passage to the leaves.
© 2014 Pearson Education, Inc.
The leaves at the top of a tree's canopy are exposed to direct
sunlight during the day, and their phytochromes will occur in a
high _____ ratio. Meanwhile, the leaves of the same tree at the
bottom of the canopy are highly shaded during the day and will
likely have a higher proportion of the _____ form of phytochrome
present due to exposure to a higher proportion of _____ light.
a) Pfr/Pr; Pr; red
b) Pfr/Pr; Pfr; far-red
c)
Pr/Pfr; Pr; far-red
d) Pfr/Pr; Pr; far-red
e) Pfr/Pr; Pfr; red
© 2014 Pearson Education, Inc.
The leaves at the top of a tree's canopy are exposed to direct
sunlight during the day, and their phytochromes will occur in a
high _____ ratio. Meanwhile, the leaves of the same tree at the
bottom of the canopy are highly shaded during the day and will
likely have a higher proportion of the _____ form of phytochrome
present due to exposure to a higher proportion of _____ light.
a) Pfr/Pr; Pr; red
b) Pfr/Pr; Pfr; far-red
c)
Pr/Pfr; Pr; far-red
d) Pfr/Pr; Pr; far-red
e) Pfr/Pr; Pfr; red
© 2014 Pearson Education, Inc.
The “sleep” movements of many plants (see figure) are
repeated each day and often do not involve the formation of
any new permanent structures. Therefore, these
movements can best be considered a type of
a) response to daily changes in the magnetic field.
b) developmental response.
c) plant behavior.
d) response to daily changes
in water stress experienced
by the plant.
e) defense against herbivory
at night.
© 2014 Pearson Education, Inc.
The “sleep” movements of many plants (see figure) are
repeated each day and often do not involve the formation of
any new permanent structures. Therefore, these
movements can best be considered a type of
a) response to daily changes in the magnetic field.
b) developmental response.
c) plant behavior.
d) response to daily changes
in water stress experienced
by the plant.
e) defense against herbivory
at night.
© 2014 Pearson Education, Inc.
When a plant’s leaves experience a water potential that is
more negative than is optimal, it will attempt to restore its
leaf water potential back to optimal values by doing what?
a) leaves creating more cytokinins to help them
retain items needed to avoid senescence
b) spreading abscisic acid in its leaves to help
induce stomatal pore closure
c) promoting root elongation by moving more auxin
to the root-elongating region
d) emitting ethylene so that leaf
senescence is promoted
e) producing more florigen in its
leaf tissues
© 2014 Pearson Education, Inc.
When a plant’s leaves experience a water potential that is
more negative than is optimal, it will attempt to restore its
leaf water potential back to optimal values by doing what?
a) leaves creating more cytokinins to help them
retain items needed to avoid senescence
b) spreading abscisic acid in its leaves to help
induce stomatal pore closure
c) promoting root elongation by moving more auxin
to the root-elongating region
d) emitting ethylene so that leaf
senescence is promoted
e) producing more florigen in its
leaf tissues
© 2014 Pearson Education, Inc.
Which choice INCORRECTLY matches an
environmental signal with a typical response in vascular
plants?
a) high osmolarity of the soil solution, production of
osmotically compensating solutes
b) gravity, negative gravitropic growth by shoots
c) flooding of the soil, production of abscisic acid
in the shoots
d) exposure of lettuce seeds to red light, promotion
of seed germination
e) High temperatures in the leaves, production of
heat-shock proteins
© 2014 Pearson Education, Inc.
Which choice INCORRECTLY matches an
environmental signal with a typical response in vascular
plants?
a) high osmolarity of the soil solution, production of
osmotically compensating solutes
b) gravity, negative gravitropic growth by shoots
c) flooding of the soil, production of abscisic acid
in the shoots
d) exposure of lettuce seeds to red light, promotion
of seed germination
e) High temperatures in the leaves, production of
heat-shock proteins
© 2014 Pearson Education, Inc.
A common feature of the innate immune systems of
many eukaryotes is the presence of
a) receptors specific for pathogen-associated
molecular structures.
b) phagocytotic cells that destroy pathogens.
c) disease resistance (R) genes.
d) enzymes that produce methyl salicylic acid.
e) expression of genes coding for factors needed for
systemic acquired resistance.
© 2014 Pearson Education, Inc.
A common feature of the innate immune systems of
many eukaryotes is the presence of
a) receptors specific for pathogen-associated
molecular structures.
b) phagocytotic cells that destroy pathogens.
c) disease resistance (R) genes.
d) enzymes that produce methyl salicylic acid.
e) expression of genes coding for factors needed for
systemic acquired resistance.
© 2014 Pearson Education, Inc.
The systemic acquired resistance seen in vascular
plants lasts for several days. If, once activated, this
system was kept always on, then one result might be
a) the accumulation of methyl salicylic acid in the
roots of the plant.
b) higher rates of infection by other types of pathogens.
c) the spread of more pathogenic effectors into the
plant tissues.
d) reduced growth rate of the plant, due to the
metabolic costs of deploying this system of
resistance.
e) the production of more gibberellins to promote
plant stem elongation.
© 2014 Pearson Education, Inc.
The systemic acquired resistance seen in vascular
plants lasts for several days. If, once activated, this
system was kept always on, then one result might be
a) the accumulation of methyl salicylic acid in the
roots of the plant.
b) higher rates of infection by other types of pathogens.
c) the spread of more pathogenic effectors into the
plant tissues.
d) reduced growth rate of the plant, due to the
metabolic costs of deploying this system of
resistance.
e) the production of more gibberellins to promote
plant stem elongation.
© 2014 Pearson Education, Inc.