Question 1

A pathogenic fungus invades a plant.What does the infected plant produce in response to the attack?

Accepted Answer

A) antisense RNA 
B) phytoalexins 
C) phytochrome 
D) statoliths 
E) thickened cellulose microfibrils in the cell wall

Question 2

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?

Accepted Answer

A) circadian rhythm 
B) photoperiodic response 
C) phototropic response 
D) biological clock 
E) thigmomorphogenesis

Question 3

Trees found at high elevations tend to be short with stocky tree trunks compared to trees growing in more sheltered areas.The term that describes plants' sensitivity to mechanical stress is

Accepted Answer

A) thigmomorphogenesis. 
B) thigmotropism. 
C) statolithogenesis. 
D) florigenesis. 
E) vernalization.

Question 4

Plant hormones produce their effects by

Accepted Answer

A) altering the expression of genes. 
B) modifying the permeability of the plasma membrane. 
C) modifying the structure of the nuclear envelope membrane. 
D) altering the expression of genes and modifying the permeability of the plasma membrane. 
E) modifying the permeability of the plasma membrane and modifying the structure of the nuclear envelope membrane.

Question 5

Which of the following plant hormones would most likely be found in high concentrations in a mature,slightly overripe fruit?

Accepted Answer

A) auxins and cytokinins 
B) auxins and abscisic acid 
C) gibberellins and cytokinins 
D) cytokinins and ethylene 
E) abscisic acid and ethylene

Question 6

Auxins (IAA)in plants are known to affect all of the following phenomena except

Accepted Answer

A) geotropism of shoots. 
B) maintenance of dormancy. 
C) phototropism of shoots. 
D) inhibition of lateral buds. 
E) fruit development.

Question 7

In extremely cold regions,woody species may survive freezing temperatures by

Accepted Answer

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) increasing cytoplasmic levels of specific solute concentrations, such as sugars.

Question 8

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. 
E) Auxins and gibberellins are transported to the vacuoles to build up turgor pressure.

Question 9

According to modern ideas about phototropism in plants

Accepted Answer

A) light causes auxin to accumulate on the shaded side of a plant stem. 
B) auxin indirectly inhibits elongation of plant stem cells. 
C) auxin is produced by the apical meristem of the coleoptile and moves downward. 
D) all hormones move downward via the xylem. 
E) cytokinins are more directly involved than auxins.

Question 10

How does indoleacetic acid affect fruit development?

Accepted Answer

A) by preventing pollination 
B) by inhibiting formation of the ovule 
C) by promoting gene expression in cambial tissue 
D) by promoting rapid growth of the ovary 
E) by inducing the formation of brassinosteroids

Question 11

Both red and blue light are involved in

Accepted Answer

A) stem elongation. 
B) photoperiodism. 
C) positive phototropism. 
D) tracking seasons. 
E) all of the above.

Question 12

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.

Accepted Answer

A) auxin 
B) calcium 
C) statoliths 
D) light 
E) differential growth

Question 13

Which of the following conclusions is supported by the research of Frits Went 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) Agar contains a chemical substance that mimics a plant hormone. 
C) A chemical substance involved in shoot bending is produced in shoot tips. 
D) Once shoot tips have been cut, normal growth cannot be induced. 
E) Light stimulates the synthesis of a plant hormone that responds to light.

Question 14

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 15

Which of the following field treatments would be most likely to result in a wheat or corn field with most of the plants of uniform height?

Accepted Answer

A) auxin spray early in the season 
B) gibberellin spray early in the season 
C) abscisic acid spray late in the season 
D) auxin spray late in the season 
E) auxin and gibberellin spray late in the season

Question 16

Jasmonates are important in which of the following processes?
I.play a key role in the time-keeping processes of plants
II.control plant defenses against herbivores and pathogens
III.regulate physiological processes such as nectar secretion and fruit ripening
IV.suppress adventitious root formation
V.induce the opening of stomata

Accepted Answer

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

Question 17

A long-day plant will flower if

Accepted Answer

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 far-red light.

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 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

Question 19

Which event during the evolution of land plants favored the synthesis of secondary compounds?

Accepted Answer

A) the greenhouse effect throughout the Devonian period 
B) the reverse-greenhouse effect during the Carboniferous period 
C) the association of the roots of land plants and fungi 
D) the rise of herbivory

Question 20

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. 
E) ethylene.

Exam 39: Plant Responses to Internal and External Signals