Deck 28: External Factors and Plant Growth

Question 1

Experiments on cocklebur have shown that the ______ perceives the photoperiod.

A)apical meristem
B)columella
C)leaf blade
D)petiole
E)stem

Answer 1

C

Question 2

Which of the following statements concerning hydrotropism is FALSE?

A)It is the directed growth of roots in response to moisture.
B)Decapped roots do not curve hydrotropically.
C)Under normal gravity, hydrotropism is suppressed by gravitropism.
D)Auxin apparently is required for hydrotropism.
E)Inhibitors of auxin influx and efflux also inhibit hydrotropism.

Answer 2

E

Question 3

In roots and shoots, the statoliths are:

A)chloroplasts.
B)amyloplasts.
C)plasma membranes.
D)cell walls.
E)lignified cells.

Answer 3

B

Question 4

Light with a wavelength of about ______ nanometers is the most effective for interrupting the dark period of both short-day and long-day plants.

A)220
B)340
C)440
D)660
E)730

Question 5

According to the original hypothesis on negative gravitropism of shoots, auxin is redistributed to the ______ side where it ______ cell expansion.

A)lower; stimulates
B)lower; inhibits
C)upper; stimulates
D)upper; inhibits
E)upper; first inhibits then stimulates

Question 6

In the current model of root gravitropism, elongation is _____ in the upper side of the distal elongation zone and ______ along the lower side.

A)stimulated; stimulated
B)stimulated; suppressed
C)suppressed; stimulated
D)suppressed; is neither stimulated nor suppressed
E)is neither stimulated nor suppressed; suppressed

Question 7

Which of the following statements about thigmotropism is FALSE?

A)It enables roots to navigate around rocks.
B)It is a response to contact with a solid object.
C)An example is the climbing of tendrils.
D)Cells touching the support lengthen more than cells on the other side.
E)The stems of peas can store the memory of tactile stimulation.

Question 8

Which of the following statements concerning the phytochrome molecule is FALSE?

A)The phytochromes in Arabidopsis are encoded by just 2 genes.
B)Most plants have several different phytochromes.
C)The chromophore portion is similar to the phycobilins in cyanobacteria.
D)One part is a protein.
E)The chromophore portion absorbs light.

Question 9

Suppose lettuce seeds are exposed to a series of alternating flashes of red light (abbreviated R) and far-red light (abbreviated FR).(E.g., a flash of red light followed by a flash of far-red light is denoted as R→RF.) Which of the following series of flashes would result in the germination of those seeds?

A)FR only
B)R→FR
C)R→FR →R→FR
D)R →FR→R→FR→R
E)R→FR→R→FR→R→FR

Question 10

When lettuce seeds are exposed to red light:

A)P_fr is converted to P_r.
B)P_r is converted to P_fr.
C)660-nanometer light is converted to 730-nanometer light.
D)730-nanometer light is converted to 660-nanometer light.
E)they will not germinate.

Question 11

Which of the following statements about P_r and P_fr is FALSE?

A)They are photoreceptors.
B)They participate in photoconversion reactions.
C)P_r is the biologically active form.
D)P_r absorbs 660-nanometer light.
E)P_fr absorbs 730-nanometer light.

Question 12

Which of the following statements concerning photoperiodism is FALSE?

A)Short-day plants in the early spring or fall.
B)Spinach and lettuce are examples of long-day plants.
C)Day-neutral plants flower without respect to photoperiod.
D)Photoperiodic behavior remains constant over a wide range of temperatures.
E)In some plants, only a single exposure to the critical day-length will produce a response.

Question 13

In roots, statoliths are localized in the:

A)endodermis.
B)vascular tissues.
C)starch sheath.
D)epidermis of the root cap.
E)root cap columella.

Question 14

Which of the following is NOT a finding from experiments on the role of auxin in phototropism of coleoptile tips?

A)Light does not affect the total amount of auxin.
B)Light does not destroy auxin.
C)Auxin migrates from the lighted side to the shaded side.
D)More auxin can be isolated from the shaded side of an intact tip than from the lighted side.
E)If the tip is split and the two halves separated by a barrier, more auxin can be isolated from the shaded side than from the lighted side.

Question 15

______ light is the most effective in producing a phototropic response.

A)Green
B)Yellow
C)Orange
D)Blue
E)Red

Question 16

When a growing root is oriented horizontally, the amyloplasts in the central column of the rootcap:

A)slide downward.
B)float upward.
C)attach to the nuclear envelope.
D)attach to the mitochondria.
E)do not move.

Question 17

Long-day plants flower:

A)in the summer.
B)in early spring or fall.
C)when exposed to eight hours of daylight.
D)when the light period is shorter than a critical length.
E)without respect to day length.

Question 18

In terms of the circadian clock, gating refers to the observation that stimuli of _____ strength employed at different times of the day can result in ______ intensity of response.

A)different; a smaller
B)different; the same
C)different; different
D)equal; the same
E)equal; a different

Question 19

Which of the following statements about circadian clocks is FALSE?

A)Input pathways and output pathways are the parts of the clock that do not interact.
B)Conceptually they consist of three parts.
C)They cause the regular oscillation of 30-40 percent of Arabidopsis genes.
D)The central oscillator is the part of the clock that generates rhythmic behavior.
E)Input pathways are the part of the clock that carries information to the oscillator.

Question 20

If a short-day plant receives a one-minute exposure to light in the middle of the dark period rather than continuous darkness, it will:

A)produce more flowers.
B)produce smaller flowers.
C)produce larger flowers.
D)flower at a lower temperature.
E)not flower.

Question 21

The rapid closure of leaves of the Venus flytrap is now thought to be due to:

A)changes in turgor pressure in the cells beneath the epidermis.
B)changes in turgor pressure in the upper epidermis.
C)changes in turgor pressure in cells of the pulvinus.
D)acid-induced wall loosening of motor cells.
E)unloading of sucrose from the phloem.

Question 22

In Mimosa pudica, movement of leaflets involves all of the following changes in cells of the pulvinus EXCEPT:

A)accumulation of sucrose unloaded from the phloem.
B)an influx of potassium ions from the apoplast.
C)a change in turgor pressure.
D)an efflux of water.
E)a decrease in water potential.

Question 23

The direction of a nastic movement is always ______ the direction of the stimulus.

A)away from
B)toward
C)at right angles to
D)at an oblique angle to
E)independent of

Question 24

In temperate regions, the acclimation of buds is initiated primarily by decreasing ______, and it produces ______.

A)daylength; cold hardiness
B)temperature; cold hardiness
C)moisture; moisture resistance
D)levels of growth inhibitors; early flowering
E)numbers of bud scales; early flowering

Question 25

In contrast to thigmonastic movements, thigmomorphogenesis:

A)is a response to touch.
B)is a response to a mechanical stimulus.
C)is independent of the direction of the stimulus.
D)involves cells of the pulvinus.
E)involves an altered growth pattern.

Question 26

In the process of vernalization, early ______ is stimulated by exposing the germinating seeds to ______ temperatures.

A)dormancy; low
B)flowering; low
C)germination; low
D)dormancy; high
E)germination; high

Question 27

When phytochromes interact with PIF proteins, what happens next?

A)The PIF proteins bind DNA.
B)The PIF proteins enter the endoplasmic reticulum.
C)The PIF proteins enter the nucleus.
D)The PIF proteins are degraded.
E)The PIF proteins are polymerized.

Question 28

The florigen FT is produced in:

A)vessel elements.
B)companion cells.
C)tracheids.
D)sieve-tube elements.
E)guard cells.

Question 29

Which of the following statements about a pulvinus is FALSE?

A)It is a joint-like thickening at the base of a leaf or a leaflet.
B)It is responsible for most nyctinastic leaf movements.
C)It lacks vascular tissue.
D)It contains parenchyma cells.
E)Some of its cells undergo changes in turgor.

Question 30

In nyctinastic movements, leaves:

A)twine around a support such as a fence post.
B)have their stomata open during the night and closed during the day.
C)are rolled during the day and unrolled at night.
D)are oriented vertically in darkness and horizontally in light.
E)are oriented horizontally in darkness and vertically in light.

Question 31

Compared with similar plants growing in full sunlight, plants growing in the shade of other vegetation:

A)receive more red light and less far-red light.
B)are usually shorter.
C)receive more wavelengths below 700 nanometers than above.
D)have a reduced red/far-red ratio.
E)receive more reflected light and less transmitted light.

Question 32

Which of the following statements about heliotropism is FALSE?

A)It is a diurnal movement involving pulvini.
B)It is a process involving an orientation to the sun.
C)It involves the leaves and flowers of many plants.
D)It is also called solar tracking.
E)It involves a mechanism similar to that of stem phototropism.
True-False Questions

Question 33

Vernalization takes place directly in the cells of the:

A)shoot apical meristem.
B)leaf blade.
C)petiole.
D)stem.
E)hypocotyl.

Question 34

In Arabidopsis, what is the correct order of action of the following flower-promoting genes?

A)FT then GI then CO
B)CO then FT then GI
C)CO then GI then FT
D)GI then CO then FT
E)FT then CO then GI

Question 35

Stratification is the process used by horticulturalists in which seeds are:

A)moistened and exposed to low temperature.
B)moistened and exposed to high temperature.
C)mechanically abraded.
D)soaked in alcohol.
E)dried.

Question 36

An etiolated eudicot seedling:

A)has a short stem.
B)has small leaves.
C)is green.
D)lacks plastids.
E)cannot undergo further growth.

Question 37

Which of the following statements about bud scales is FALSE?

A)They may contain growth inhibitors.
B)They protect the bud against desiccation.
C)They restrict the movement of oxygen into the bud.
D)They insulate the bud from heat loss.
E)They have leaf primordia in their axils.

Question 38

If a leaf is given an inductive cycle and then removed immediately the plant _____, but if the leaf is removed several hours after photoinduction, then the plant _______.

A)won't flower; won't flower
B)will flower; won't flower
C)won't flower; will flower
D)won't be vernalized; will be vernalized
E)will be vernalized; won't be vernalized

Question 39

Winter rye is usually planted in the ______, and it flowers in the ______.

A)early spring; summer
B)early spring; autumn
C)early spring; winter
D)summer; following spring
E)autumn; following summer

Question 40

In Arabidopsis thaliana, touch induces the expression of genes that encode proteins related to ______, suggesting a role for ______ in thigmomorphogenesis.

A)an endogenous inhibitor; the biological clock
B)amylase; starch
C)the cytoskeleton; microtubules
D)calmodulin; calcium
E)chlorophyll; magnesium

Question 41

The floral stimulus can move across a graft as well as through agar.

Question 42

Vernalization is the exposure of flower buds to low temperatures to promote early flowering.

Question 43

In Arabidopsis, the floral stimulus is produced in companion cells of leaves.

Question 44

If lettuce seeds are exposed first to red light followed immediately by exposure to far-red light the seeds will germinate.

Question 45

In tropisms, a response toward the stimulus is said to be negative.

Question 46

In the shoot, the gravity-sensing cells are called statoliths.

Question 47

Circadian rhythms persist even when all environmental conditions are kept constant.

Question 48

In roots, statocytes are located in the root cap.

Question 49

In order to flower, short-day plants must have a light period shorter than a critical length, and long-day plants must have a light period longer than a critical length.

Question 50

Experiments using ¹⁴C-labeled auxin indicate that light causes the destruction of auxin in coleoptiles.

Question 51

The wavelength of light most effective in causing germination of lettuce seeds is 730 nanometers.

Question 52

Seed dormancy can usually be overcome by placing the seeds in a warm, moist environment.

Question 53

With respect to effect on flowering, the middle of the dark period is the part most sensitive to interruption by a flash of light.

Question 54

Photoperiodism pertains to events that are influenced by the relative lengths of light and dark.

Question 55

In Arabidopsis, the FT gene encodes the FT protein, which is the florigen.

Question 56

In shoot gravitropism, auxin is distributed to the lower side where it stimulates cell expansion.

Question 57

An example of thigmotropism is the twisting growth of tendrils.

Question 58

Phytochrome-interacting factors (PIFs) are located in the nucleus.

Question 59

In the process of scarification, seeds are treated with solvents that dissolve the waxes in the seed coat.

Question 60

The ageotropum mutant of pea plants lacks both a hydrotropic response and a gravitropic response.

Question 61

The seismonastic movements of Mimosa pudica involve changes in the pulvini.

Question 62

Regular rubbing or bending of a stem stimulates its elongation.

Question 63

The sleep movements of plants are an example of nastic movements.

Question 64

The bulbs of tulips and hyacinths can be "forced" by bringing them indoors before the temperature drops.

Question 65

Cold hardiness refers to the process of preparing the plant for winter.