Deck 33: Control Systems in Plants

Question 1

Which of the following statements about plant hormones is true?

A)Plant hormones mainly affect reproductive processes.
B)Individual hormones typically have single,specific effects.
C)Plant hormones are produced in very small concentrations.
D)Plant hormones play a vital role in photosynthesis.

Answer 1

C

Question 2

Which of the following hormones might induce seeds treated with it to break dormancy?

A)ethylene
B)a gibberellin
C)an auxin
D)a cytokinin

Answer 2

B

Question 3

Which plant in Went's experiment shows auxin stimulating elongation in the left side of the plant only?

A)plant A
B)plant B
C)plant C
D)plant D

Answer 3

C

Question 4

Which class of hormones produced in the roots of plants promotes cell division and growth,and retards the aging of flowers and leaves?

A)phytochromes
B)ethylene
C)cytokinins
D)gibberellins

Question 5

A plant's first line of defense against infection is

A)salicylic acid.
B)R genes.
C)its epidermis.
D)Avr genes.

Question 6

The most reliable way to stimulate branching in a plant is to

A)give short- day light treatments.
B)add extra fertilizer.
C)remove the terminal bud.
D)apply auxin to the axillary buds.

Question 7

Which of the following would be a good way to ripen a green tomato?

A)placing it under a bright light for 24 hours
B)placing it in a microwave,on low power,for 5 minutes
C)putting it in a darkened area such as a drawer or box
D)placing it in a sealed plastic bag with an overripe banana

Question 8

Which of the following is a way that plants use animals as a defense against herbivores?

A)attraction of wasps that kill herbivorous caterpillars
B)coevolution between plants and predators
C)production of an amino acid that harms herbivores
D)release of microbe- killing chemicals in response to infection

Question 9

If the auxin that is produced by an apical meristem is transported in equal amounts down all sides of a twig,the twig will probably

A)elongate evenly.
B)flower.
C)bend away from the apical meristem.
D)branch near its tip.

Question 10

Bush beans grow as small bushes rather than as vines because their internodes are short and they branch close to the apical meristem.Which of the following substances,if applied to a bush bean,might cause it to revert to a vine habit?

A)abscisic acid
B)a cytokinin
C)ethylene
D)a gibberellin

Question 11

Grass shoots bend toward the light because,on the shadowed side,a(n)

A)reduction in auxin levels prevents cell elongation.
B)increase in auxin levels promotes cell elongation.
C)reduction in auxin levels promotes cell elongation.
D)increase in auxin levels promotes cell division.

Question 12

Which of the following processes underlies the thigmotropic behavior of a green bean tendril?

A)slower growth on the side where an object is touching the tendril
B)extra proliferation of cells on the shaded side of the tendril
C)rotation of the tendril in response to photoperiod
D)rotation of the tendril in response to a biological clock

Question 13

A biologist interested in determining which plant organs (stems,buds,leaves,etc.)are responsible for sensing photoperiod might perform which of the following experiments?

A)measure auxin levels in different parts of the plant before and after exposure to light
B)cover different plant organs with a foil covering to prevent light exposure
C)expose the plants to different wavelengths of light
D)remove the apical meristems from different parts of the plant

Question 14

In many grocery stores,fresh fruits are sold prebagged in plastic bags dotted with holes so that they will not overripen.The main function of the holes is to

A)facilitate diffusion of O2 to the fruit.
B)prevent buildup of CO2.
C)permit the fruit to drain after being washed.
D)facilitate diffusion of ethylene away from the fruit.

Question 15

Which of the following is the factor that initiates flowering in long- day plants?

A)nights longer than a critical length
B)days longer than the intervening nights
C)days shorter than a critical length
D)nights shorter than a critical length

Question 16

Which hormone prevents a seed released in the fall from germinating immediately?

A)abscisic acid
B)gibberellins
C)auxins
D)ethylene

Question 17

What term refers to seasonal changes in the relative lengths of night and day?

A)photoperiod
B)phototaxis
C)circadian rhythm
D)gravitropism

Question 18

Which of the following is one adaptive advantage for deciduous plants that lose their leaves during the winter?

A)A layer of leaves on the ground helps keep plant roots warm.
B)Production of new leaves each spring is more efficient than supporting old leaves all winter.
C)It prevents water loss from leaves when soil water is unavailable due to freezing.
D)If leaves are damaged by frost,the tree will die.

Question 19

Which type of plant hormone generally acts as a growth inhibitor?

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

Question 20

Under what conditions would you expect a plant to have the highest concentration of abscisic acid?

A)in a houseplant growing in low light conditions
B)in a desert after a long drought
C)in a wet tropical rain forest
D)in a cool environment after a heavy rain

Question 21

In leaf abscission,the abscission layer forms where the

A)root joins the stem.
B)leaf stalk joins the stem.
C)axillary bud joins the stem.
D)leaf stalk joins the leaf.

Question 22

When a nursery worker pinches off the terminal buds on a young chrysanthemum plant to make it grow bushy,which of the following plant hormones is mainly responsible for growth of side branches?

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

Question 23

Which of the following substances induces "bolting," the rapid elongation of a plant stem?

A)ethylene
B)phytochrome
C)abscisic acid
D)a gibberellin

Question 24

A plant will only flower if the night length is longer than 14 hours.This plant is a

A)short- day plant.
B)long- day plant.
C)day- neutral plant.
D)short- night plant.

Question 25

The event that triggers fruit formation is the growth of a pollen tube through the carpel of a flower.Which of the following would be a reasonable hypothesis about the basis of this effect?

A)Pollen tubes grow in response to abscisic acid.
B)The growing pollen tube produces ethylene.
C)The growing pollen tube produces auxins and/or gibberellins.
D)Pollen tubes grow in response to a cytokinin produced by the carpel.

Question 26

Which of the following is a health benefit associated with increasing the amount of soybeans in the human diet?

A)decreased amount of fiber in the diet
B)removal of antioxidants from the body
C)decreased LDL levels
D)decreased HDL levels

Question 27

Which of the following options lists the events leading to leaf fall in deciduous trees in the correct order?

A)shortening days,increase in ethylene production,formation of abscission layer
B)shortening days,formation of abscission layer,decrease in ethylene levels
C)formation of abscission layer,increase in ethylene levels,decrease in auxin levels
D)decrease in ethylene levels,shortening days,formation of abscission layer

Question 28

Which of the following plant responses is affected by photoperiod?

A)cell division
B)onset of dormancy
C)gravitropism
D)apical dominance

Question 29

Christmas cactus is a short- day plant that usually blooms in the winter.Which of the following strategies might induce it to bloom for the 4th of July?

A)putting it in a cool,well- lighted place from time to time during June
B)leaving it in a dark closet all night and part of each morning during June
C)exposing it to light several times during each night in June
D)putting it in a dark closet for a short time every afternoon during June

Question 30

What is one main effect of auxins on plant growth?

A)They reduce growth by inhibiting cell division.
B)Auxins have no effect on plant growth.
C)They increase growth by promoting cell elongation.
D)They increase growth by increasing the rate of photosynthesis.

Question 31

Which of the following statements is supported by this figure?

A)Auxin concentrations above 0.9 g/L are best for promoting stem elongation.
B)Auxin concentrations around 10- 4 g/L promote stem elongation but inhibit root elongation.
C)The greater the concentration of auxin,the more promotion of root elongation occurs.
D)Auxin concentrations below 10- 8 g/L promote both root and stem elongation.

Question 32

Which of the following growth responses causes the shoots of a plant grown in the dark to grow upward?

A)thigmotropism
B)gravitropism
C)phototropism
D)photoperiodism

Question 33

Fruit that forms on an unpollinated plant in response to a hormone will lack

A)rind.
B)seeds.
C)naturally occurring hormones.
D)flavor.

Question 34

Salicylic acid,the main component of aspirin,may be an example of a(n)

A)alarm hormone.
B)amino acid that,when consumed by an insect,will kill that insect.
C)substance that attracts wasps to a plant being eaten by caterpillars.
D)substance encoded for by Avr genes.

Question 35

Shoot branching is controlled mainly by the interaction of

A)gibberellins and cytokinins.
B)auxins and cytokinins.
C)auxins and gibberellins.
D)cytokinins and abscisic acid.

Question 36

Which of the following statements concerning biological clocks is false?

A)Movement of plants long distances very quickly induces a kind of plant "jet lag."
B)Biological clocks are strongly influenced by external temperatures.
C)Circadian rhythms occur with or without external stimuli.
D)Innate circadian rhythms generally differ slightly from a 24- hour period.

Question 37

Plants grow toward light through the action of

A)chloroplasts.
B)nerves.
C)solar energy.
D)hormones.

Question 38

About how many gibberellins have been identified in plants?

A)thousands
B)over one hundred
C)five
D)one

Question 39

Synthetic auxins are used commercially

A)to promote flowering in ornamental crops.
B)to promote seed germination.
C)to promote side branching to produce bushier crops.
D)as a broadleaf weed killer.

Question 40

What stimulates germination of desert plant seeds after a hard rain?

A)cooler temperatures
B)activation of cytokinins
C)removal of abscisic acid
D)production of auxins

Question 41

Mimosa plants spread their leaflets during the day and fold them at night.You decide to design an experiment to test whether Mimosa's leaf movements are controlled by a biological clock.Which of the following experiments would be the best test of your hypothesis?

A)Putting the plant in a dark closet at nightfall.Check on the plant in the morning about 10 hours later,while the plant is still in the closet.If the leaves are open,a biological clock is indicated.
B)Growing the plant indoors and turning the lights on in the middle of the night.If a biological clock is controlling leaf movement,the leaves will open.
C)Subjecting the plant to a flash of red light in the middle of the night.If the leaves open at the usual time the next morning,a biological clock mechanism is ruled out.
D)Putting the plant in a dark closet in the middle of the day.If the leaves close,a biological clock mechanism is ruled out.

Question 42

What dense storage granules in plant cells are thought to contribute to gravitropism?

A)starch
B)proteins
C)chlorophyll
D)cellulose

Question 43

The plant growth response to touch is known as

A)gravitropism.
B)thigmotropism.
C)bolting.
D)geotropism.

Question 44

There is concern over the use of dioxin,a synthetic plant hormone,as a weed killer because

A)it weakens the shells of the eggs of predatory birds,resulting in the death of their offspring.
B)it causes massive fish kills when it gets into lakes and streams.
C)it can cause irreversible mutations in crop plants.
D)it can cause birth defects and leukemia in mammals.

Question 45

One of the experiments in phototropism involved cutting off the tips of grass seedlings before exposing them to light from one side.The decapitated seedlings did not bend toward light.A valid conclusion from this experiment would be that

A)light is perceived by the tip of grass plants.
B)plants cannot engage in photosynthesis without the tip of the plant.
C)hormones are produced in all parts of the plant.
D)a foil cover over the tip of the seedlings would cause them to bend.

Question 46

How does phytochrome control flowering?

A)by determining whether day length exceeds a critical minimum
B)by inducing differentiation of cells in the apical meristem
C)by sensing sunrise and sunset
D)by determining whether day length is shorter than a critical maximum