Deck 39: Plant Sensory Systems, signals, and Responses

Question 1

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.Why would it be advantageous to move chloroplasts within cells?

A)to maximize light absorption by the chloroplasts for photosynthesis
B)to increase production of phototropic hormones
C)to maximize heat absorption by the chloroplasts for cellular respiration
D)to increase ATP production during the light-independent reactions
E)all of the above

Answer 1

A

Question 2

What do phototropin,zeaxanthin,and cryptochrome all have in common?

A)They control stomatal pore size.
B)They are all involved in stem growth.
C)They are all blue-light receptors.
D)They are all localized to root cells.

Answer 2

C

Question 3

Lettuce seeds need full sunlight to germinate;therefore,germination is inhibited when their phytochrome molecules are in the Pfᵣ conformation.

Answer 3

False

Question 4

To understand how plant phototropic responses are regulated,a researcher performed the following experiment.He exposed oat seedlings to light and then cut off tips of coleoptiles and placed them on agar blocks.Later the agar blocks were placed on decapitated coleoptiles of other individuals,and some seedlings were kept in the dark while others were exposed to light.Based on your knowledge of auxin synthesis and mode of action,predict in what cases the decapitated coleoptiles would bend to the right.

A)when the block was placed on the left side of the coleoptiles in both dark and light treatments
B)when the block was placed on the right side of the coleoptiles in both dark and light treatments
C)when the block was placed on the left side of the coleoptiles in dark only
D)when the block was placed on the right side of the coleoptiles in dark only
E)as long as light was coming from the right,decapitated coleoptiles bent to the right independently of agar block placement

Question 5

Put the following events of the acid-growth hypothesis in order.
1)Cell wall softens and expands.
2)Sugar enters the cell via proton cotransporters.
3)Protons are pumped out of the cell by H⁺-ATPases.
4)Positively charged ions enter the cell.
5)New cellulose microfibrils are produced to extend cell length.
6)Water enters the cell via osmosis,and the cell swells.

A)1,3,5,6,2
B)3,6,4,3,2,1
C)6,4,3,1,2,5
D)3,4,2,6,1,5
E)6,1,2,4,3,5

Question 6

When Charles and Francis Darwin first documented phototropism,why was it important that they germinated the grass seeds in the dark before beginning the experiment?

A)so the young shoots would grow slowly
B)so the young shoots would grow quickly
C)so the young shoots would grow straight
D)so the young shoots would be soft enough to bend

Question 7

How does auxin binding to the auxin receptor trigger cell elongation?

A)A signal transduction cascade causes additional proton pumps to be made,and those proteins pump protons up their concentration gradient and out of the cell.
B)A signal transduction cascade causes proton channels to open,and protons flow down their concentration gradient and out of the cell.
C)The auxin receptor is a proton channel that opens in response to auxin binding,allowing protons to flow down their concentration gradient and into the cell.
D)The auxin receptor begins phosphorylating proton pumps,activating them to pump protons up their concentration gradient and out of the cell.
E)A signal transduction cascade results in the opening of a water pore that allows water into the cell,causing it to swell.

Question 8

Mammalian eyes sense light because they contain cells having molecules called opsins,which change structure when exposed to light.Which of the following plant molecule(s)would be analogous to mammalian opsins in their light-sensing ability?

A)auxin and phototropins
B)auxin and Pfᵣ
C)Pfᵣ and phototropins
D)cytokinins and phototropins
E)ABA and Pfᵣ

Question 9

The addition of a phosphate group to a protein is called _____,and it usually results in _____.

A)dephosphorylation;protein activation or inactivation
B)phosphorylation;protein activation or inactivation
C)phosphorylation;creation of more ATP
D)dephosphorylation;creation of different proteins

Question 10

An eccentric millionaire botanist has offered a $25,000 scholarship to anyone who can successfully get a plant to grow through a vertical maze in complete darkness.The maze is not in a box;the maze is simply drawn on the wall,and the contestants must get their plant to grow in a pattern that matches the path through the maze.You need the money and feel confident that you can accomplish this task.Which of the following techniques will help you succeed?

A)Apply auxin directly to the shoot tip on the side to which you want the tip to bend.
B)Apply auxin directly to the lower part of the stem opposite from the direction you want the stem to bend.
C)Inject compounds that block auxin receptors into the part of the stem opposite from the direction you want the stem to bend.
D)Plant the roots in two different pots,and apply auxin to the root bucket that is on the same side as the direction you want the plant to bend.

Question 11

Table 39.1

Refer to Table 39.1.Plant B is a short-day flower.Why did it fail to flower?

A)It sensed a nine-hour night.
B)It sensed a nine-hour day.
C)Flowering was inhibited by the excess of far-red light.
D)There was not enough blue-light exposure to trigger flowering.

Question 12

To find the gene that encodes for the blue-light receptor,researchers inserted the gene for the PHOT1 protein into insect cells growing in culture.When they exposed the transgenic cells to blue light,they found that the PHOT1 protein became phosphorylated.No other plant proteins were present in the insect cells.Which of the following is a reasonable conclusion from this result?

A)The PHOT1 protein enabled the insect cells to photosynthesize.
B)The PHOT1 protein phosphorylated itself in the presence of blue light.
C)The PHOT1 protein is not responsive to blue light.
D)The PHOT1 protein is photoreversible.
E)The PHOT1 protein is not functional in insect cells.

Question 13

Table 39.1

Refer to Table 39.1.Plant C is a long-day plant.

Question 14

Table 39.1

Refer to Table 39.1.How would Plant A be classified? Assume all plants are able to produce flowers.

A)long day
B)short day
C)day-neutral

Question 15

Which of the following is not a characteristic of plant hormones?

A)They exist in plants in very tiny amounts.
B)They change their shape in response to stimulus.
C)They are able to move from one cell to another cell through extracellular spaces.
D)They affect only cells having an appropriate receptor.
E)All of the above are correct descriptions of plant hormones.

Question 16

Which of the following cannot be sensed by plants?

A)gravity
B)pathogens
C)wind
D)light
E)none of the above

Question 17

Which of the following cell activity would not be triggered by a signal transduction cascade?

A)change in ion flow through a membrane channel
B)activation of transcription
C)activation of translation
D)release of secondary messenger

Question 18

You grew reed canary grass seedlings in the dark and cut off their tips.Then you placed tips on agar blocks,one in dark and one in light.Based on your knowledge of auxin movement and stability in light,predict the concentration of auxin in the agar blocks.

A)The block in the light should have more auxin;one in the dark will have less.
B)The block in the dark should have more auxin;one in the light will have less.
C)The block in the light should have some auxin;one in the dark will have none.
D)The block in the dark should have some auxin;one in the light will have none.
E)Both blocks will have an equal amount of auxin.

Question 19

Which of the following is the correct sequence of events after a receptor perceives a signal?

A)The receptor is phosphorylated and then changes its shape.This leads to activation of gene transcription and finally to release of hormone from the cell.
B)The receptor is phosphorylated and then changes its shape.This leads to hormone release from the cell,which activates gene transcription.
C)The receptor changes its shape and then becomes phosphorylated.This leads to hormone release from the cell,which activates gene transcription.
D)The receptor changes its shape and then becomes phosphorylated.This leads to activation of gene transcription and finally to release of hormone from the cell.

Question 20

The cells that have phosphorylated phototropin receptors elongate in response to blue light.

Question 21

Which of the following is the strongest evidence that cytokinins regulate cell divisions?

A)increase of cyclin gene expression in tissues exposed to cytokinin
B)decrease of cyclin gene expression in tissues exposed to cytokinin
C)induction of shoot growths in tissues exposed to cytokinin
D)induction of root growths in tissues exposed to cytokinin
E)ability of cytokinin to interact with auxin at the molecular level and change auxin biosynthesis and transport

Question 22

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

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 some of the higher branches off at the stem.
E)Cut off the leaves at the base of most of the branches.

Question 23

If a Venus flytrap were treated with a drug that inhibited the H⁺-ATPase,which of the following would likely happen?

A)Its cells would become depolarized.
B)It would not be able to close its flytraps.
C)It would not be able to reopen its flytraps once closed.

Question 24

Why does Arabidopsis have five genes that code for phytochrome?

A)They mediate different types of responses to red/far-red light.
B)Several of them sense red light and the others sense far-red light.
C)All five phytochrome absorb different types of light,maximizing sensitivity of a plant to it.
D)Some of the phytochromes do not function in light absorption but regulate other processes.

Question 25

Which of the following signals indicates shade to a plant?

A)light quantity
B)blue light
C)far-red light
D)red light

Question 26

What will a plant sensitive to touch or vibration look like when it is repeatedly touched or exposed to wind?

A)It will be taller and thinner.
B)It will be taller and thicker.
C)It will be shorter and thicker
D)It will be shorter and thinner.

Question 27

Suppose a plant had a nonsense mutation in a gene that encodes for an enzyme required for the synthesis of gibberellic acid.If the plant is homozygous at this locus,what will its phenotype be?

A)tall
B)bushy
C)short
D)large fruit
E)underdeveloped seeds

Question 28

Suppose a plant had a photosynthetic pigment that absorbed far-red wavelengths of light.In which of the following environments could that plant thrive?

A)on the floor of a lake,whose water contains abundant green algae
B)on the forest floor,beneath a canopy of taller plants
C)on the ocean floor,in very deep waters
D)on mountaintops,closer to the Sun

Question 29

If cells in the _____ are removed,roots will no longer respond to gravity.

A)root hairs
B)zone of elongation
C)root cap
D)secondary meristem

Question 30

What hormones are necessary for maintenance of plant tissue culture?

A)gibberellins and auxin
B)gibberellins and cytokinin
C)gibberellins and ABA
D)auxin and ABA
E)auxin and cytokinin

Question 31

Figure 39.2

Suppose you laid a seedling on its side so that the root was parallel to the ground.Several hours after the change in position,where in the root cells (position A,B,or C in Figure 39.2)would you find the amyloplasts?

A)A
B)B
C)C

Question 32

In lettuce seeds,blue light initiates germination.If you measured hormone levels within the seed,which hormone would be produced upon exposure to blue light?

A)gibberellin
B)ethylene
C)abscisic acid
D)cytokinins
E)brassinosteroids

Question 33

Shoots that grow vertically toward the Sun can be characterized as _____.

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 34

Figure 39.2

Suppose you laid a seedling on its side so that the root was parallel to the ground.Immediately after the change in position,where in the root cells (position A,B,or C in Figure 39.2)would you find the amyloplasts? The answer should be one of the positions shown in Figure 39.2.

A)A
B)B
C)C

Question 35

_____ in concentration of auxin in shoot cells and _____ in concentration of auxin in root cells lead to cell elongation.

A)Increase;increase
B)Increase;decrease
C)Decrease;increase
D)Decrease;no change

Question 36

Antisense gene sequences can be used to block the transcription of specific genes in a cell or group of cells.Suppose you took a cutting from a plant and treated it with an antisense gene that would block the transcription of an enzyme involved in auxin production.What would happen to your cutting?

A)Photosynthesis would decrease.
B)It would grow to be very tall and thin.
C)Adventitious root growth would be greatly reduced.
D)It would not be able to initiate a hypersensitive response.
E)All of the above answers apply.

Question 37

Why does auxin move through the plant slower than sucrose does?

A)Auxin transport is active (requires energy)while sucrose transport is passive.
B)Auxin is transported by diffusion while cotransporters are involved in sucrose transport.
C)Auxin transport through phloem is slower than sucrose transport through parenchyma cells.
D)Auxin transport through parenchyma cells is slower than sucrose transport through phloem.
E)Both auxin and sucrose are transported through phloem and parenchyma cells,but auxin is a bigger molecule and moves slower by diffusion.

Question 38

_____ prevents seeds from germinating until conditions are favorable for the growth of the plant.

A)Ethylene
B)Auxin
C)Zeaxanthin
D)Gibberellin
E)Abscisic acid

Question 39

Which of the following will occur when sensory hairs in a Venus flytrap are stimulated?

A)Venus flytrap sensory cells will become hyperpolarized and potassium ions will rush into the cell.
B)Venus flytrap sensory cells will become depolarized,and the cytoplasm of the Venus flytrap sensory cells will become dehydrated due to water leaving the cell.
C)Venus flytrap sensory cells will become hyperpolarized,and the cytoplasm of the Venus flytrap sensory cells will become more negative.
D)Venus flytrap sensory cells will become depolarized,and positive ions and water will enter the Venus flytrap sensory cells.
E)Venus flytrap sensory cells will become depolarized,and the cytoplasm of the Venus flytrap sensory cells will become more negative.

Question 40

Figure 39.1

The data in Figure 39.1 were taken from a study on the effects of far-red light on stem elongation.The data indicate that plants from shady habitats do not respond to far-red light by growing taller.Which of the following would be a logical hypothesis for why these plants do not respond to far-red light?

A)The shade plants do not have phototropin.
B)The shade plants do not have protein kinases.
C)The shade plants do not have cryptochromes.
D)The shade plants do not have phytochrome.
E)All of these are reasonable hypotheses.

Question 41

Antisense gene sequences can be used to block the transcription of specific genes in a cell or group of cells.Suppose you treated a seed with an antisense sequence that blocked the transcription of GAMyb transcription factor.What would happen to the seed?

A)It would germinate too soon.
B)It would not be responsive to gibberellins.
C)It would not make abscisic acid.
D)It would not grow a hypocotyl during germination.

Question 42

A particular species of virus carries a gene for salicylate hydroxylase,an enzyme that breaks down salicylic acid.Will this virus be more or less virulent to plants than other viruses?

A)more
B)less

Question 43

If a particular species of bacterium were able to produce a substance that breaks down reactive oxygen intermediates and inhibits the production of nitric oxide,it would be less effective at infecting plant cells.

Question 44

Figure 39.3

Figure 39.3 is a Northern blot showing the expression of Myb mRNA in cultured aleurone layer cells that were treated with gibberellin versus control cells that were not treated with gibberellin.Only the gibberellin-treated cells expressed the Myb mRNA,but the Myb mRNA was not detectable until 6-12 hours after gibberellin application.Why did it take so long?

A)Gibberellin had to bind to a receptor and initiate a signal transduction cascade that in turn had to activate a transcription factor that triggered the transcription of the Myb gene.
B)Gibberellin had to diffuse into the aleurone layer cells and be metabolized in order to trigger activation of a transcription factor that triggered transcription of the Myb gene.
C)Gibberellin had to enter the cells and find the Myb gene among the large plant genome.

Question 45

A certain bacterium infects a plant's upper leaves.A few days later,bacteria of the same species attempt to infect the same plant's roots but are unsuccessful.What process is responsible for the plant's ability to prevent this infection?

A)antivirulence response
B)pathogenesis resistance
C)systemic acquired resistance
D)sequential immunity

Question 46

What do phototropin and ABA have in common?

A)They induce stomata closing.
B)They regulate opening and closing of water pores in the plasma membrane.
C)They regulate activity of H⁺-ATPases.
D)They are localized in the plasma membrane.
E)All of the above apply.

Question 47

You have discovered a previously unidentified plant,and you cultivate it in your lab.You notice that its flowers close when people are talking,yet are open when the lab is relatively quiet.You suspect that this plant may have the ability to hear! Based on what you know about plant sensation,which of the following hypotheses is the most reasonable to explain this phenomenon?

A)There is a cell-surface protein on the epidermal cells that becomes phosphorylated in response to vibration by sound waves.
B)There are tiny hairs on epidermal cells that bend in response to the vibration of sound waves,triggering an action potential in epidermal cells.
C)There is a cell-surface receptor on root cells that becomes phosphorylated when the soil vibrates in response to sound waves.
D)All of the above answers are correct.

Question 48

Use the following information when answering the corresponding question(s).
Researchers found that high doses of nitric oxide were not lethal to soybean cells.Likewise,high doses of reactive oxygen intermediates were not lethal to soybean cells.However,when combined,nitric oxide and reactive oxygen intermediates were very lethal to soybean cells.(M.Delledonne et al.2001.Signal interactions between nitric oxide and reactive oxygen intermediates in the plant hypersensitive response.Proceedings of the National Academy of Sciences,USA 98(23):13454-59. )
Refer to the paragraph on Delledonne et al.Based on the findings presented in the paragraph,combined with what you have learned about the hypersensitive response,which sequence of events occurs when a pathogen infects a plant cell? (Only some of the events will be used. )
1)The R protein binds to the avr protein.
2)The pathogen releases avr proteins.
3)The plant cell produces nitric oxide.
4)The pathogen produces reactive oxygen intermediates.
5)A signal transduction cascade occurs.
6)The plant cell and the pathogen die.
7)The pathogen dies,the plant cell lives.
8)The plant cell produces both nitric oxide and reactive oxygen intermediates.

A)1,5,8,2,7
B)2,1,5,8,6
C)2,3,4,5,7
D)2,5,4,3,6
E)1,5,4,3,7

Question 49

A caterpillar eats a leaf of a plant.The next day it crawls to a nearby leaf to eat.But after eating the second leaf,the caterpillar gets very sick and falls off the plant.Which of the following molecules were involved in the plant's ability to defend itself against the second attack?

A)proteinase inhibitors
B)systemin
C)jasmonic acid
D)proteinase inhibitors,systemin,and jasmonic acid
E)proteinase inhibitors and jasmonic acid

Question 50

In the fall,the leaves of some trees change color.This happens because chlorophyll breaks down and the accessory pigments become visible.What hormone is responsible for this?

A)phototropin
B)abscisic acid
C)cytokinin
D)ethylene
E)salicylic acid

Question 51

Use the following information when answering the corresponding question(s).
Researchers found that high doses of nitric oxide were not lethal to soybean cells.Likewise,high doses of reactive oxygen intermediates were not lethal to soybean cells.However,when combined,nitric oxide and reactive oxygen intermediates were very lethal to soybean cells.(M.Delledonne et al.2001.Signal interactions between nitric oxide and reactive oxygen intermediates in the plant hypersensitive response.Proceedings of the National Academy of Sciences,USA 98(23):13454-59. )
Refer to the paragraph on Delledonne et al.Why would the researchers study the association between cell death,nitric oxide,and reactive oxygen intermediates?

A)to gain insight into how R genes are inherited
B)to gain insight into how R proteins recognize avr proteins
C)to gain insight into what happens after R-avr protein binding
D)to gain insight into how pathogens kill plant cells

Question 52

You buy some fresh fruit at the grocery store.When you get home you are in a hurry,and you put the fresh fruit in the crisper with some overripe fruit.At the end of the week you are disappointed to find that your new fruit has already become overripe.What happened?

A)The refrigerator was probably set too high.As a result,the production of auxin was induced in overripe fruit and caused production of ethylene in the fresh fruit.
B)The fresh fruit was not washed before refrigerating,so ethylene was still present on the surface of the fruit,causing the fresh fruit to overripen.
C)The overripe fruit released ethylene that increased the rate of ripening in the fresh fruit.
D)The fresh fruit was damaged,producing ethylene that sped up the ripening process.

Question 53

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.

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

Question 54

You discover a chemical that inhibits the conversion of starch to sugar and inhibits the breakdown of chlorophyll and cellulose in fruit.Who might be interested in buying this chemical?

A)grocers,to spray on fruit to enhance ripening in the store
B)farmers,to spray on fruit after picking to stall ripening
C)consumers,to spray on fruit before eating to enhance taste
D)all of the above

Question 55

Plant A is diploid and is homozygous for all of the resistance loci.Plant B is tetraploid and is heterozygous for all of the resistance loci.Which is better able to respond to infection?

A)plant A
B)plant B

Question 56

What do abscisic acid and gibberellins have in common?

A)They work together to induce germination by triggering the metabolism of endosperm nutrients.
B)They both induce the formation of transcription factors that bind to the α-amylase promoter.
C)They are both released from roots to signal drought to the leaves and stimulate the opening of stomata.
D)They bind to the same cell-surface receptor on cells of the aleurone layer in seeds.

Question 57

If you wanted to genetically engineer a plant to be more resistant to attack by pathogenic bacteria and viruses,which of the following hormones would you manipulate?

A)auxin
B)gibberellins
C)abscisic acid
D)ethylene
E)salicylic acid

Question 58

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)_____.

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

Question 59

A particular parasitoid is heterozygous for a gene that binds plant pheromones.Which of the following is true of that parasitoid?

A)It will be particularly successful at infecting plants.
B)It will be responsive to the signals released from several plants.
C)It will be unable to respond to a plant's distress call.
D)It will be able to attract more mates.

Question 60

A certain species of bacterium is not very effective at colonizing potato plants because the potato plants have a resistance gene that responds to the presence of the bacterium.Which of the following mutations would make the bacterium more successful at invading the potato plant?

A)a mutation in the plant's resistance gene that made it heterozygous,leading to a mutant gene product that is able to recognize different avirulence factors
B)a mutation in the bacterial avirulence gene that made the avirulence factor unable to bind to the plant's resistance factor
C)a mutation in the plant's resistance gene that made the resistance factor able to bind more tightly to the avirulence factor
D)a mutation in the bacterial avirulence gene that made the avirulence factor able to bind to a different resistance factor in the plant

Question 61

Use the following information when answering the corresponding question(s).
The shade avoidance response is a plant's way of changing its growth pattern when it is being shaded by another plant.Upon exposure to shade,many plants will grow taller,flatten their leaf angle,and extend their leaves further from their stems in order to reach full sunlight.Research performed by Pierik et al.(Interactions between ethylene and gibberellins in phytochrome-mediated shade avoidance responses in tobacco.2004.Plant Physiology 136:2928-36;online at http://www.plantphysiol.org/cgi/content/full/136/2/2928)examined the role of ethylene and gibberellins on the shade avoidance response in tobacco plants.The shade avoidance response is known to involve phytochromes.
Refer to the paragraph on the research done by Pierik et al.Ethylene's role in the shade avoidance response in tobacco plants is related to its role in fruit ripening,leaf abscission,and senescence.

Question 62

Use the following information when answering the corresponding question(s).
Some plants have continually produced secondary defense compounds.Other plants are induced to form secondary defense compounds when they are injured.Corn seedling leaves that are chewed on by the caterpillars of a type of cutworm moth emit immediate volatile chemicals (LOX products),and after 6 hours large amounts of terpenoid compounds are released into the air.The terpenoids are released not only from the leaf being chewed,but from all leaves of the plant.The terpenoid compounds attract a parasitoid wasp female that lays her eggs on the caterpillar.When the wasp larvae hatch,they eat and kill the moth caterpillar.(T.C.J.Turlings,J.H.Loughrin,P.J.McCall,U.S.R.Rose,W.J.Lewis,and J.H.Tumlinson.1995.How caterpillar-damaged plants protect themselves by attracting parasitic wasps.Proceedings of the National Academy of Sciences 92:4169-74. )
Refer to the paragraph on how caterpillar-damaged plants protect themselves by attracting parasitic wasps.What can you conclude based only on the information in the preceding paragraph?

A)The attracting terpenoid compounds are always present in the corn seedling.
B)Physical injury by the caterpillar mouthparts causes the production of terpenoids.
C)Chemical signals from the caterpillar saliva attract the parasitic wasp.
D)The parasitoid wasp is attracted by compounds produced by an injured corn plant.
E)LOX products and terpenoids are the same kinds of chemical compounds.

Question 63

Use the following information when answering the corresponding question(s).
The shade avoidance response is a plant's way of changing its growth pattern when it is being shaded by another plant.Upon exposure to shade,many plants will grow taller,flatten their leaf angle,and extend their leaves further from their stems in order to reach full sunlight.Research performed by Pierik et al.(Interactions between ethylene and gibberellins in phytochrome-mediated shade avoidance responses in tobacco.2004.Plant Physiology 136:2928-36;online at http://www.plantphysiol.org/cgi/content/full/136/2/2928)examined the role of ethylene and gibberellins on the shade avoidance response in tobacco plants.The shade avoidance response is known to involve phytochromes.
Refer to the paragraph on the research done by Pierik et al.When the researchers inhibited the synthesis of gibberellins in the tobacco plants,neither ethylene nor far-red light could trigger a shade avoidance response.Taken together with the data presented above,these data suggest that gibberellins _____.

A)act in concert (work together)with ethylene to generate the shade avoidance response
B)antagonize (act oppositely)the effects of ethylene on the shade avoidance response
C)are not involved in the shade avoidance response

Question 64

Use the following information when answering the corresponding question(s).
Some plants have continually produced secondary defense compounds.Other plants are induced to form secondary defense compounds when they are injured.Corn seedling leaves that are chewed on by the caterpillars of a type of cutworm moth emit immediate volatile chemicals (LOX products),and after 6 hours large amounts of terpenoid compounds are released into the air.The terpenoids are released not only from the leaf being chewed,but from all leaves of the plant.The terpenoid compounds attract a parasitoid wasp female that lays her eggs on the caterpillar.When the wasp larvae hatch,they eat and kill the moth caterpillar.(T.C.J.Turlings,J.H.Loughrin,P.J.McCall,U.S.R.Rose,W.J.Lewis,and J.H.Tumlinson.1995.How caterpillar-damaged plants protect themselves by attracting parasitic wasps.Proceedings of the National Academy of Sciences 92:4169-74. )
Refer to the paragraph on how caterpillar-damaged plants protect themselves by attracting parasitic wasps.How could you test the hypothesis that compounds from the caterpillar alone do not attract parasitoid wasps?

A)Have caterpillars feed on different kinds of plants in the presence of the wasps.
B)Place non-feeding caterpillars in an enclosure with the wasps.
C)Place intact corn seedlings in an enclosure with the wasps.

Question 65

Use the following information when answering the corresponding question(s).
The shade avoidance response is a plant's way of changing its growth pattern when it is being shaded by another plant.Upon exposure to shade,many plants will grow taller,flatten their leaf angle,and extend their leaves further from their stems in order to reach full sunlight.Research performed by Pierik et al.(Interactions between ethylene and gibberellins in phytochrome-mediated shade avoidance responses in tobacco.2004.Plant Physiology 136:2928-36;online at http://www.plantphysiol.org/cgi/content/full/136/2/2928)examined the role of ethylene and gibberellins on the shade avoidance response in tobacco plants.The shade avoidance response is known to involve phytochromes.
Refer to the paragraph on the research done by Pierik et al.When tobacco plants were exposed to far-red light,they exhibited increased stem length,petiole length,and petiole angle.These three responses are part of the shade avoidance response.When the same plants were exposed to small concentrations of ethylene while being exposed to far-red light,they exhibited even greater increases in stem length,petiole length,and petiole angle.In a subsequent experiment,tobacco plants showed an increase in ethylene production in response to far-red light.Moreover,mutant plants that are insensitive to ethylene did not show a shade avoidance response when exposed to far-red light.Taken together,these data suggest that ethylene _____.

A)inhibits growth when tobacco plants are shaded by other plants
B)stimulates growth when tobacco plants are shaded by other plants
C)triggers leaf abscission when tobacco plants are shaded by other plants
D)is not involved in the shade avoidance response

Question 66

Use the following information when answering the corresponding question(s).
Some plants have continually produced secondary defense compounds.Other plants are induced to form secondary defense compounds when they are injured.Corn seedling leaves that are chewed on by the caterpillars of a type of cutworm moth emit immediate volatile chemicals (LOX products),and after 6 hours large amounts of terpenoid compounds are released into the air.The terpenoids are released not only from the leaf being chewed,but from all leaves of the plant.The terpenoid compounds attract a parasitoid wasp female that lays her eggs on the caterpillar.When the wasp larvae hatch,they eat and kill the moth caterpillar.(T.C.J.Turlings,J.H.Loughrin,P.J.McCall,U.S.R.Rose,W.J.Lewis,and J.H.Tumlinson.1995.How caterpillar-damaged plants protect themselves by attracting parasitic wasps.Proceedings of the National Academy of Sciences 92:4169-74. )
Refer to the paragraph on how caterpillar-damaged plants protect themselves by attracting parasitic wasps.How could you test the hypothesis that caterpillar saliva and a wound are both necessary to attract the parasitoid wasps?

A)Slash the corn leaves with a razor blade.
B)Put caterpillar saliva on a leaf wound.
C)Put caterpillar saliva on an intact leaf.
D)All of the above actions are necessary for testing the hypothesis.