Question 1

Which of the following can function in signal transduction in plants?
I calcium ions
II nonrandom mutations
III receptor proteins
IV autochrome
V secondary messengers

Accepted Answer

A)   only I, III, and IV
B)   only I, II, and V
C)   only I, III, and V
D)   only II, III, and V C

Question 2

If a farmer wanted more loosely packed clusters of grapes, he would most likely spray the immature bunches with ________.

Accepted Answer

A)   auxin
B)   gibberellins
C)   cytokinins
D)   abscisic acid B

Question 3

Which of the following mechanisms is in the correct sequence of steps (I-IV as listed below)that takes place during the formation of de-etiolation (greening)response proteins in plants?
I Detection of light signal
II Activation of phytochrome
III Activation of specific protein kinase1
IV Formation of de-etiolation response protein

Accepted Answer

A)   I, III, II, and IV
B)   I, II, III, and IV
C)   II, I, III, and IV
D)   III, I, II, and IV B

Question 4

Plants often use changes in day length (photoperiod)to trigger events such as dormancy and flowering. It is logical that plants have evolved this mechanism because photoperiod changes ________.

Accepted Answer

A)   are more predictable than air temperature changes
B)   predict moisture availability
C)   are modified by soil temperature changes
D)   can reset the biological clock

Question 5

Generally, each hormone has multiple functions in plants depending on ________.
I site of action
II its concentration
III developmental stage
IV age

Accepted Answer

A)   I, II, III, and IV
B)   I, II, and III
C)   I and II
D)   II

Question 6

Upon exposure to blue light, plants not only begin to grow toward the light, but move their chloroplasts to the sunny side of each cell. The adaptive advantage of moving chloroplasts to the sunny side of each cell ________.

Accepted Answer

A)   maximizes light absorption by the chloroplasts for photosynthesis
B)   increases production of phototropic hormones
C)   maximizes heat absorption by the chloroplasts for cellular respiration
D)   increases adenosine triphosphate (ATP)  production during the light-independent reactions

Question 7

Auxins in plants are known to affect which of the following processes?
I gravitropism of shoots
II maintenance of seed dormancy
III phototropism of shoots
IV inhibition of lateral buds
V apical dominance

Accepted Answer

A)   only I and II
B)   only I, III, and V
C)   only I, III, IV, and V
D)   only II, III, IV, and V

Question 8

What are the primary sites of ethylene production in high concentrations in plants?

Accepted Answer

A)   shoot apical meristem and young leaves
B)   roots
C)   seeds
D)   ripening fruits

Question 9

Which of the following conclusions is supported by the research of both Peter Boysen-Jensen and Charles and Francis Darwin on shoot responses to light?

Accepted Answer

A)   When shoots are exposed to light, a chemical substance migrates toward the light.
B)   A chemical substance involved in shoot bending is produced in shoot tips.
C)   Once shoot tips have been cut, normal growth cannot be induced.
D)   Light stimulates the synthesis of a plant hormone that responds to light.

Question 10

Shoots that grow vertically toward the sun can be characterized as ________.

Accepted Answer

A)   positive for phototropism and negative for gravitropism
B)   neutral for phototropism and positive for gravitropism
C)   negative for phototropism and positive for gravitropism
D)   positive for phototropism and neutral for gravitropism

Question 11

A population of plants experiences several years of severe drought. Much of the population dies due to lack of water, but a few individuals survive. You set out to discover the physiological basis for their adaptation to such an extreme environmental change. You hypothesize that the survivors have the ability to synthesize higher levels of ________ than their siblings do.

Accepted Answer

A)   auxin
B)   gibberellin
C)   cytokinin
D)   abscisic acid

Question 12

Auxin enhances cell elongation in all of these ways except

Accepted Answer

A)   increased uptake of solutes.
B)   gene activation.
C)   acid-induced denaturation of cell wall proteins.
D)   cell wall loosening.

Question 13

Plant hormones ________.

Accepted Answer

A)   in plant cells naturally exist in very large amounts
B)   change their shape in response to stimulus
C)   are unable to move from one cell to another
D)   affect only cells with the appropriate receptor

Question 14

You are out working in your garden, and you notice that one of your favorite flowering plants has black, dead spots on the leaves. You immediately suspect that the plant has been invaded by a pathogen and has initiated a(n)________.

Accepted Answer

A)   avirulence response
B)   hypersensitive response
C)   resistance response
D)   virulence response

Question 15

Use the figure to answer the following question.

Suppose you laid a seedling on its side so that the root was parallel to the ground as shown in the figure. Several hours after the change in position, where in the root cells, position A, B, or C in the figure, would you find the amyloplasts?

Accepted Answer

A)   A
B)   B
C)   C
D)   A and C

Question 16

Apical dominance in plants is under the control of ________.

Accepted Answer

A)   sugar
B)   various plant hormones
C)   cell division
D)   sugar and various plant hormones

Question 17

Which of the following statements best summarizes the acid growth hypothesis in an actively growing shoot?

Accepted Answer

A)   Auxin stimulates proton pumps in the plasma membrane and tonoplast.
B)   Auxin-activated proton pumps lower the pH of the cell wall, which breaks bonds and makes the walls more flexible.
C)   Auxins and gibberellins together act as a lubricant to help stretch cellulose microfibrils.
D)   Auxins activate aquaporins that increase turgor pressure in the cells.

Question 18

How may a plant respond to severe heat stress?

Accepted Answer

A)   by reorienting leaves to increase evaporative cooling
B)   by creating air tubes for ventilation
C)   by producing heat-shock proteins, which may protect the plant's proteins from denaturing
D)   by increasing the proportion of unsaturated fatty acids in cell membranes, reducing their fluidity

Question 19

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 ________.

Accepted Answer

A)   negative thigmotropism
B)   negative phototropism
C)   negative gravitropism
D)   the opposite of circadian rhythms

Question 20

You have a small tree in your yard that is the height that you want it, but does not have as many branches as you want. How can you prune it to trigger it to increase the number of branches?

Accepted Answer

A)   Cut off the leaves at the ends of several branches.
B)   Cut off the tips of the main shoots.
C)   Cut off lower branches.
D)   Cut off the leaves at the base of most of the branches.

Exam 39: Plant Responses to Internal and External Signals

Which of the following can function in signal transduction in plants? I calcium ions II nonrandom mutations III receptor proteins IV autochrome V secondary messengers