60) If the range of a species of plants expands to a higher latitude, which of the following processes is
the most likely to be modified by natural selection?
A) circadian rhythm
B) photoperiodic response
C) phototropic response
D) biological clock
E) thigmomorphogenesis
61) What does a short-day plant require in order to flower?
A) a burst of red light in the middle of the night
B) a burst of farfired light in the middle of the night
C) a day that is longer than a certain length
D) a night that is longer than a certain length
E) a higher ratio of Pr to Pfr
62) If a short-day plant has a critical night length of 15 hours, then which of the following 24-hour
cycles will prevent flowering?
A) 8 hours light/16 hours dark
B) 4 hours light/20 hours dark
C) 6 hours light/2 hours dark/light flash/16 hours dark
D) 8 hours light/8 hours dark/light flash/8 hours dark
E) 2 hours light/20 hours dark/2 hours light
63) A long-day plant will flower if
A) the duration of continuous light exceeds a critical length.
B) the duration of continuous light is less than a critical length.
C) the duration of continuous darkness exceeds a critical length.
D) the duration of continuous darkness is less than a critical length.
E) it is kept in continuous farfired light.
64) Plants that have their flowering inhibited by being exposed to bright lights at night are
A) day-neutral plants.
B) short-night plants.
C) devoid of phytochrome.
D) short-day plants.
E) long-day plants.
65) Classic experiments suggested that a floral stimulus, florigen, could move across a graft from an
induced plant to a noninduced plant and trigger flowering. Recent evidence using Arabidopsis has
recently shown that florigen is probably
A) a phytochrome molecule that is activated by red light.
B) a protein that is synthesized in leaves, travels to the shoot apical meristems, and initiates flowering.
C) a membrane signal that travels through the symplast from leaves to buds.
D) a second messenger that induces Ca++ ions to change membrane potential.
E) a transcription factor that controls the activation of florigen-specific genes.
66) A short-day plant exposed to nights longer than the minimum for flowering but interrupted by short
flashes of light
A) never flower.
B) might flower depending upon the duration of the light flash.
C) will not be affected and will flower.
D) might flower depending upon the wavelengths of the light flashes.
E) will still flower if ethylene is administered.
67) A long-day plant will flower
A) in the late fall.
B) when the night is shorter than a critical value.
C) only under artificial light in the summer.
D) during short days with proper fertilization.
E) regardless of the photoperiod imposed.
68) What do the results of research on gravitropic responses of roots and stems show?
A) Different tissues have the same response to auxin.
B) The effect of a plant hormone can depend on the tissue.
C) Some responses of plants require no hormones at all.
D) Light is required for the gravitropic response.
E) Cytokinin can only function in the presence of auxin.
69) Which of the following best describes positive gravitropism exhibited by plant roots?
A) It is mediated by auxin similar to the phototropism responses in shoots.
B) It depends on an inhibition of elongation of some cells.
C) Gravity causes gibberellins to accumulate on the lower side of roots.
D) The phenomenon depends upon inhibition of cell elongation of certain root cells by abscisic acid.
E) All of the above are correct.
70) Vines in tropical rain forests must grow toward large trees before being able to grow toward the sun.
To reach a large tree, the most useful kind of growth movement for a tropical vine presumably would be
the opposite of
A) positive thigmotropism.
B) positive phototropism.
C) positive gravitropism.
D) sleep movements.
E) circadian rhythms.
71) A botanist discovers a plant that lacks the ability to form starch grains in root cells, yet the roots still
grow downward. This evidence refutes the long-standing hypothesis that
A) falling statoliths trigger gravitropism.
B) starch accumulation triggers the negative phototropic response of roots.
C) starch grains block the acid growth response in roots.
D) starch is converted to auxin, which causes the downward bending in roots.
E) starch and downward movement are necessary for thigmotropism.
72) Which of the following watering regimens will be most effective at keeping a lawn green during the
hot, dry summer months?
A) daily sprinkling to soak the soil to 0.5 inch
B) sprinkling every other day to soak the soil to 1.0 inch
C) sprinkling every third day to soak the soil to 2.0 inches
D) daily sprinkling to soak the soil to 0.5 inch or sprinkling every other day to soak the soil to 1.0 inch
E) sprinkling every other day to soak the soil to 1.0 inch or sprinkling every third day to soak the soil to
2.0 inches
73) You are part of a desert plant research team trying to discover crops that will be productive in arid
climates. You discover a plant that produces a hormone under water-deficit conditions that triggers a
suite of drought responses. Most likely the hormone is
A) ABA.
B) GA.
C) IAA.
D) 2, 4-D.
E) salicylic acid.
74) If you wanted to genetically engineer a plant to be more resistant to drought, increasing amounts of
which of the following hormones might be a good first attempt?
A) abscisic acid
B) brassinosteroids
C) gibberellins
D) cytokinins
E) auxin
75) Plant cells begin synthesizing large quantities of heat-shock proteins
A) after the induction of chaperone proteins.
B) in response to the lack of CO2 following the closing of stomata by ethylene.
C) when desert plants are quickly removed from high temperatures.
D) when they are subjected to moist heat (steam) followed by electric shock.
E) whenever the external temperature exceeds the threshold where photosynthesis is negatively
impacted.
76) Most scientists agree that global warming is underway; thus, it is important to know how plants
respond to heat stress. Which of the following would be a useful line of inquiry to try and improve plant
response and survival to heat stress?
A) the production of heat-stable carbohydrates
B) increased production of heat-shock proteins
C) the opening of stomata to increase evaporational heat loss
D) protoplast fusion experiments with xerophytic plants
E) all of the above
77) In extremely cold regions, woody species may survive freezing temperatures by
A) emptying water from the vacuoles to prevent freezing.
B) decreasing the numbers of phospholipids in cell membranes.
C) decreasing the fluidity of all cellular membranes.
D) producing canavanine as a natural antifreeze.
E) increasing cytoplasmic levels of specific solute concentrations, such as sugars.
78) Which of the following is a likely response of plants to cold stress?
A) the production of a specific solute “plant coagulant ” that reduces water loss
B) reducing the size of ice crystals
C) conversion of the fluid mosaic cell membrane to a solid mosaic one
D) an increase in sterol concentration of membrane lipids so that the membranes remain flexible
E) increasing the proportion of unsaturated fatty acids in the membranes
79) Bald cypress and loblolly pine are both gymnosperm trees native to the southern United States. The
cypress grows in swamps; the pine grows in sandy soil. How do you think their anatomies differ?
A) There are larger intercellular spaces in the roots of the cypress than in the roots of the pine.
B) Water-conducting cells are larger in the stems of the cypress than in the stems of the pine.
C) The springwood and summerwood are more distinct in the cypress.
D) There is less parenchyma in the roots of the cypress than in the pine roots.
E) There are no major anatomical differences between these species because they’re both gymnosperms.
80) The initial response of the root cells of a tomato plant watered with seawater would be to
A) rapidly produce organic solutes in the cytoplasm.
B) rapidly expand until the cells burst.
C) begin to plasmolyze as water is lost.
D) actively transport water from the cytoplasm into the vacuole.
E) actively absorb salts from the seawater.
81) Which of the following best explains both the growth of a vine up the trunk of a tree as well as the
directional growth of a houseplant toward a window?
A) nastic movement
B) taxic movement
C) tropism response
D) morphological response
E) acclimation
82) The rapid leaf movements resulting from a response to touch (thigmotropism) primarily involve
A) rapid growth response.
B) potassium channels.
C) nervous tissue.
D) aquaporins.
E) stress proteins.
83) Which of the following is the most likely plant response to an attack by herbivores?
A) leaf abscission to prevent further loss
B) early flowering to try and reproduce before being eaten
C) production of chemical compounds for defense or to attract predators
D) production of physical defenses, such as thorns
E) production of thicker bark and cuticle to make it more difficult to eat
84) In order for a plant to initiate chemical responses to herbivory,
A) the plant must be directly attacked by an herbivore.
B) volatile “signal” compounds must be perceived.
C) gene-for-gene recognition must occur.
D) phytoalexins must be released.
E) it must be past a certain developmental age.
85) Plants are affected by an array of pathogens. Which of the following is a likely plant
defense/response against disease?
A) cells near the point of infection destroying themselves to prevent the spread of the infection
B) production of chemicals that repel pathogens
C) transcriptional level recognition followed by production of stress proteins
D) thickening the cuticle so that pathogens have trouble penetrating the tissues
E) stopping all xylem and phloem movement within infected tissues
86) A pathogenic fungus invades a plant. What does the infected plant produce in response to the attack?
A) antisense RNA
B) phytoalexins
C) phytochrome
D) statoliths
E) thickened cellulose microfibrils in the cell wall
87) Which of the following would be the most effective way to prevent herbivory in a non-woody plant?
A) production of the amino acid analog canavanine
B) release of insect pheromones
C) production of foul-tasting compounds
D) thickened cuticle
E) enhanced levels of salicylic acid
88) The transduction pathway that activates systemic acquired resistance in plants is initially signaled by
A) antisense RNA.
B) Pfr phytochrome.
C) salicylic acid.
D) abscisic acid.
E) red, but not farfired, light.
89) Which of the following would only be activated or upregulated after a plant has already been
infected by a pathogen?
A) phytochrome
B) salicylic acid
C) molecular chaperones
D) stress proteins
E) brassinosteroids
90) A plant will recognize a pathogenic invader
A) if it has many specific plant disease resistance (R) genes.
B) when the pathogen has an R gene complementary to the plant’s antivirulence (Avr) gene.
C) only if the pathogen and the plant have the same R genes.
D) if it has the specific R gene that corresponds to the pathogen molecule encoded by an Avr gene.
E) when the pathogen secretes Avr protein.
91) What is the probable role of salicylic acid in the defense responses of plants?
A) to destroy pathogens directly
B) to activate systemic acquired resistance of plants
C) to close stomata, thus preventing the entry of pathogens
D) to activate heat-shock proteins
E) to sacrifice infected tissues by hydrolyzing cells
92) When an arborist prunes a limb off a valuable tree, he or she usually paints the cut surface. The
primary purpose of the paint is to
A) minimize water loss by evaporation from the cut surface.
B) improve the appearance of the cut surface.
C) stimulate growth of the cork cambium to “heal” the wound.
D) block entry of pathogens through the wound.
E) induce the production of phytoalexins.
93) Plant hormonal control differs from animal hormonal control in that
A) there are no separate hormone-producing organs in plants as there are in animals.
B) all production of hormones is local in plants with little long-distance transport.
C) plants do not exhibit feedback mechanisms like animals.
D) only animal hormone concentrations are developmentally regulated.
E) only animal hormones may have either external or internal receptors.
94) Unlike animal hormones, plant hormones are mainly
A) hydrophobic molecules.
B) products of stresses in the environment.
C) small, easily transportable molecules.
D) unable to cross membranes.
E) direct products of photosynthesis.
95) In cases where plants exhibit generalized defense responses in organs distant from the infection site,
this is termed
A) hyperactive responses.
B) systemic acquired resistance.
C) pleiotropy.
D) hyperplasia.
E) general systemic response.
Art Questions
Figure 39.1
96) The heavy line in Figure 39.1 illustrates the relationship between auxin concentration and cell
growth
in stem tissues. If the same range of concentrations were applied to lateral buds, what curve(s) would
probably be produced?
A) I
B) II
C) III
D) II or III
E) I or III
Refer to Figure 39.2 to answer the following questions.
Figure 39.2
97) The results of this experiment, shown on the left of the graph (area A), may be used to
A) show that these plants can live without gibberellin.
B) show that gibberellin is necessary in positive gravitropism.
C) show that taller plants with more gibberellin produce fruit (pods).
D) show a correlation between plant height and gibberellin concentration.
E) study phytoalexins in plants.
98) This experiment suggests that the unknown amount of gibberellin in the experimental plant (B) is
approximately
A) zero.
B) 0.01 μg/mL.
C) 0.1 μg/mL.
D) 1.0 μg/mL.
E) equal to the amount of gibberellin in the shortest plant.
Scenario Questions
99) In nature, poinsettias bloom in early March. Research has shown that the flowering process is
triggered three months before blooming occurs. In order to make poinsettias bloom in December, florists
change the length of the light-dark cycle in September. Given the information and clues above, which of
the following is a correct statement about poinsettias?
A) They are short-day plants.
B) They require a light period longer than some set minimum.
C) They require a shorter dark period than is available in September.
D) The dark period can be interrupted without affecting flowering.
E) They will flower even if there are brief periods of farfired illumination during the nighttime.
100) A botanist exposed two groups of the same plant species to two photoperiods–one with 14 hours of
light and 10 hours of dark and the other with 10 hours of light and 14 hours of dark. Under the first set
of conditions, the plants flowered, but they failed to flower under the second set of conditions. Which of
the following conclusions would be consistent with these results?
A) The critical night length is 14 hours.
B) The plants are short-day plants.
C) The critical day length is 10 hours.
D) The plants can convert phytochrome to florigen.
E) The plants flower in the late spring.
End-of-Chapter Questions
The following questions are from the end-of–chapter “Test Your Understanding” section in Chapter 39
of the textbook.
101) The hormone that helps plants respond to drought is
A) auxin.
B) gibberellin.
C) cytokinin.
D) ethylene.
E) abscisic acid.
102) Auxin enhances cell elongation in all of the these ways except
A) increased uptake of solutes.
B) gene activation.
C) acid-induced denaturation of cell wall proteins.
D) increased activity of plasma membrane proton pumps.
E) cell wall loosening.
103) Charles and Francis Darwin discovered that
A) auxin is responsible for phototropic curvature.
B) auxin can pass through agar.
C) light destroys auxin.
D) light is perceived by the tips of coleoptiles.
E) red light is most effective in shoot phototropism.
104) How may a plant respond to severe heat stress?
A) by reorienting leaves to increase evaporative cooling
B) by creating air tubes for ventilation
C) by initiating a systemic acquired resistance response
D) by increasing the proportion of unsaturated fatty acids in cell membranes, reducing their fluidity
E) by producing heat-shock proteins, which may protect the plant’s proteins from denaturing
105) The signaling molecule for flowering might be released earlier than usual in a long-day plant
exposed to flashes of
A) farfired light during the night.
B) red light during the night.
C) red light followed by farfired light during the night.
D) farfired light during the day.
E) red light during the day.
106) If a long-day plant has a critical night length of 9 hours, which 24-hour cycle would prevent
flowering?
A) 16 hours light/8 hours dark
B) 14 hours light/10 hours dark
C) 15.5 hours light/8.5 hours dark
D) 4 hours light/8 hours dark/4 hours light/8 hours dark
E) 8 hours light/8 hours dark/light flash/8 hours dark
107) A plant mutant that shows normal gravitropic bending but does not store starch in its plastids
would require a reevaluation of the role of ________ in gravitropism.
A) auxin
B) calcium
C) statoliths
D) light
E) differential growth
108) Which type of mutant would be most likely to produce a bushier phenotype?
A) auxin overproducer
B) strigolactone overproducer
C) cytokinin underproducer
D) gibberellin overproducer
E) strigolactone underproducer