Deck 32: Plant Defense: Keeping the World Green

Question 1

Rhizobium radiobacter can be classified as a(n):

A)necrotrophic pathogen.
B)biotrophic pathogen.
C)viral pathogen.
D)epiphytic pathogen.

Answer 1

B

Question 2

A novel, unknown pathogen is devastating a particular crop, with nearly 100% mortality of infected plants. You find that the spread of disease within infected plants can be stopped by removing the bark and stem tissue (down to the vascular cambium) in a band around infected stems, and that the first signs of necrosis are rings of dead cells surrounding (completely or in part) apparently living tissue. You then assay the cells inside the necrotic rings expecting to find a high concentration of:

A)chitin.
B)double-stranded RNA.
C)AVR proteins.
D)necrotrophic pthogens.

Answer 2

B

Question 3

Which of the following statements is TRUE regarding the RNA of plant viruses?

A)Outside of replication, the RNA of plant viruses is typically single-stranded.
B)Outside of replication, the RNA of plant viruses is typically double-stranded.
C)Plants cleave viral double-stranded RNA to form small interfering RNAs.
D)Plants cleave viral single-stranded RNA to form small interfering RNAs.
E)Plant viruses contain only single-stranded DNA, not RNA.

Answer 3

A, C

Question 4

You are asked to evaluate a research proposal that aims to increase the resistance of wheat to a new stem rust by inserting R-genes from another plant, a wild relative of potato, known to be highly resist to rust. Do you recommend the proposal be funded, and why?

A)Yes, because the additional R-genes will likely improve the ability of wheat plants to recognize the rust pathogen.
B)Yes, because these R-genes come from a distantly related plant lineage, it is unlikely that this wheat rust will have evolved a way to evade them.
C)No, because these R-genes come from a distantly related plant lineage, they are unlikely to function properly in wheat.
D)No, because R-genes only confer resistance when expressed in the same species they evolved in.

Question 5

You are screening tomato varieties for plants that will resist a novel biotrophic pathogen. You should choose those with:

A)a strong hypersensitive response.
B)fewer plasmodesmata connecting cells.
C)a high diversity of AVR proteins.
D)a high diversity of R proteins.

Question 6

You are studying a plant protein that contains motifs similar to known receptors for chitin. You expect that this protein could be:

A)an AVR protein.
B)an R protein.
C)inserted in the plant cell plasma membrane.
D)inserted in the plant cell endoplasmic reticulum.
E)None of the answer options is correct.

Question 7

Which of the following statements is TRUE regarding the systemic acquired resistance (SAR) response in plants?

A)It is pathogen-specific.
B)It relies on salicylic acid.
C)It is only effective against biotrophic pathogens.
D)Strong SAR responses are associated with tissue necrosis.

Question 8

Recall that plants produce physical barriers (e.g., a cuticle or bark) to prevent pathogen infections. How can a pathogen enter, and ultimately infect, its host plant?

A)through the stomata
B)through wounds made by insects
C)through wounds made by farming equipment
D)by being drawn up from the soil with water

Question 9

Which of the following are points of entry through which viral and bacterial pathogens can infect plant tissues?

A)sites of herbivore damage
B)open stomata
C)the cuticle
D)leaf hairs

Question 10

A researcher comes across a plant that has been infected by a pathogen. As a result of the infection, the plant has undergone a systemic acquired resistance (SAR) response and has also generated several siRNAs. Based on this response, what type of pathogen MOST likely infected the plant?

A)a bacterium
B)a virus
C)a fungi
D)an oomycete
E)a parasitic plant

Question 11

Which of the following organisms can act as plant pathogens?

A)mistletoe
B)nematodes
C)tobacco plants
D)bacteria
E)P) ferruginea ants

Question 12

A botanist is studying the effects of different oomycete species on potato plants. He exposes one set of plants to an oomycete species having several avirulence (AVR) proteins. He exposes another set of plants to an oomycete species having a single AVR protein. What do you expect will be the results of his experiment?

A)Mortality will be higher in plants exposed to the oomycete species having several AVR proteins.
B)Mortality will be higher in plants exposed to the oomycete species having a single AVR protein.
C)Mortality rates will be the same in both plant sets.

Question 13

The ability of plants to wall off infections through the coordinated death of a cordon of uninfected cells provides a first line of defense against:

A)viruses.
B)fungi.
C)oomycetes.
D)bacteria.
E)herbivores.

Question 14

The level of siRNA in cells infected by Rhizobium radiobacter will:

A)be higher in order to "silence" expression of pathogen genes.
B)be lower because the pathogen has probably disabled the infected cell's ability to make siRNA.
C)remain the same because the formation of siRNAs is an immune response to viral pathogens.

Question 15

A plant's siRNA response is triggered by the presence of:

A)double-stranded RNA.
B)single-stranded RNA.
C)double-stranded DNA.
D)single-stranded DNA.

Question 16

The oomycetes that infected and killed potato plants during the Irish Potato Famine can be classified as a(n) _____ pathogen.

A)virulent
B)necrotrophic
C)avirulent
D)biotrophic

Question 17

You are screening tomato varieties for plants that will resist a novel necrotrophic pathogen. You should choose those with:

A)a strong hypersensitive response.
B)fewer plasmodesmata connecting cells.
C)thicker and stronger cell walls.
D)a high diversity of R proteins.

Question 18

In an experiment, you find that exposing leaves to methyl salicylic acid vapor prior to exposing them to a pathogen results in an avirulent infection, whereas exposing untreated control leaves to the same pathogen results in virulent infection. This is likely an example of:

A)systemic acquired resistance.
B)a hypersensitive response.
C)a small interfering RNA response.
D)phloem signaling.

Question 19

Which of the following would you expect to be effective in combating infections by pathogens similar to Rhizobium radiobacter?

A)basal resistance
B)R proteins
C)hypersensitive response
D)systemic acquired resistance
E)siRNA

Question 20

Which of the following plant and/or pathogen proteins are involved in highly specific immune responses?

A)flagellin receptors on the plasma membrane
B)avirulence (AVR)proteins formed by pathogens
C)resistance (R)proteins formed by plants
D)chitin receptors on the plasma membrane

Question 21

Which of the following is NOT part of plant defense systems against pathogens?

A)Protein receptors detect a broad class of molecules produced by many pathogens and mount defense mechanisms.
B)R proteins inside plant cells recognize AVR proteins from pathogens.
C)Plants reinforce barriers, such as by closing stomata and reinforcing cell walls.
D)Cells surrounding the infection site produce reactive oxygen species.
E)Plants produce AVR proteins when invaded by a pathogen.

Question 22

Which of the following does NOT occur as a result of infection by Rhizobium radiobacter?

A)Other tumors will form farther away from the original gall if the tumor metastasizes and moves through the phloem.
B)DNA isolated from the tumor will be from both the plant and Rhizobium.
C)Carbon compounds that are not synthesized elsewhere in the plant will be synthesized in the tumor.
D)The cells of the crown gall are all descended from the original infected cells.

Question 23

The type of defense in which plants produce chemicals that cause the uninfected cells around a site of infection to die, leading to isolation of the infected region, is called:

A)systemic acquired resistance.
B)biotrophic defense.
C)avirulent resistance.
D)the hypersensitive response.
E)the wilting response.

Question 24

Plants are able to defend themselves against viruses that have invaded their cells by:

A)producing antibodies.
B)recognizing viral RNA and interrupting its replication.
C)causing the virus to detach from the cell membrane before it injects its RNA.
D)producing sticky proteins on the cell surface that capture the viruses.
E)increasing the number of plasmodesmata per cell.

Question 25

The movement of RNA through plasmodesmata is an important mode of cell to cell signaling, but also furnishes a pathway for the spread of infection by:

A)fungi.
B)bacteria.
C)oomycetes.
D)viruses.

Question 26

MOST plant viruses have genomes made of:

A)single-stranded DNA.
B)double-stranded DNA.
C)proteins.
D)single-stranded RNA.
E)double-stranded RNA.

Question 27

Virulent bacteria are always damaging to plants and thus have no beneficial uses.

Question 28

Which of the following plant responses targets a SPECIFIC organism (i.e., would not be considered a "general" response")?

A)a basal immune response
B)R proteins recognizing AVR proteins
C)a systemic acquired resistance response
D)siRNA

Question 29

A tobacco farmer is walking through her fields. On a tobacco plant leaf, she notices several small brown spots surrounded by what appears to be necrotic or dying tissue. What likely caused these spots and necrotic patches?

A)The plant is demonstrating a hypersensitive response.
B)The plant was recently eaten by caterpillars.
C)The plant is demonstrating a SAR response.
D)The plant is producing terpenes.

Question 30

In specific resistance, if the plant does not have an appropriate R protein, which of the following will happen when it comes into contact with a pathogen?

A)The AVR proteins of the virus will not be able to bind and the plant will not become infected.
B)The AVR protein will block the plant's basal resistance, allowing the pathogen to infect the cell.
C)The AVR protein will activate the plant's defensive genes.
D)The AVR protein will bind to a receptor in the plant cell's membrane and a general defense response will be triggered.
E)The pathogen will not make AVR proteins if the plant cell lacks the R protein.

Question 31

The tobacco mosaic virus (TMV) is an example of a(n) _____ pathogen, as it requires living tobacco plant cells to survive. The TMV cannot pass through dead plant tissue such as that produced by a hypersensitive response.

Question 32

Choose the option that places the following events in plant defense in the CORRECT order.
1) The plant cell recognizes double-stranded RNA (dsRNA) as foreign and cleaves it into fragments.
2) Single-stranded RNA (ssRNA) molecules bind to the protein-bound small interfering RNA (siRNA) and are destroyed.
3) A virus infects the host plant, injecting ssRNA into the cell.
4) The viral genome is replicated and dsRNA molecules are formed.
5) siRNA bind to a plant protein complex, which retains only one of the RNA strands.

A)3 $\rightarrow$ 2 $\rightarrow$ 1 $\rightarrow$ 4 $\rightarrow$ 5
B)1 $\rightarrow$ 2 $\rightarrow$ 4 $\rightarrow$ 3 $\rightarrow$ 5
C)5 $\rightarrow$ 3 $\rightarrow$ 4 $\rightarrow$ 2 $\rightarrow$ 1
D)1 $\rightarrow$ 2 $\rightarrow$ 3 $\rightarrow$ 4 $\rightarrow$ 5
E)3 $\rightarrow$ 4 $\rightarrow$ 1 $\rightarrow$ 5 $\rightarrow$ 2

Question 33

Some plants gain their nutrition by parasitizing other plants.

Question 34

Plants harbor hundreds of protein receptors called _____ proteins, which enable them to resist specific pathogens.

A)R
B)AVR
C)S
D)TMV
E)V

Question 35

In R. radiobacter bacteria, the _____ contains bacterial genes that can be directly inserted into a plant's DNA.

Question 36

The first line of plant defense against pathogen infection is/are the:

A)cuticle.
B)plasmodesmata.
C)stomata.
D)pathogens.
E)cell walls.

Question 37

You are examining a field of crop plants and notice that many of the leaves have small scattered necrotic spots on them, but none are completely diseased. You then examine the shoot apical meristems of the plants and notice that the most recently formed internodes and leaves are expanding to their usual size. You conclude that the infection is likely:

A)necrotrophic
B)biotrophic
C)virulent
D)avirulent

Question 38

The uninfected tissues of plants capable of systemic acquired resistance (SAR) will be unable to resist infection if diseased tissue undergoes necrosis.

Question 39

How do pathogens enter into plant tissues?

A)through wounds or damaged tissues
B)through the stomata
C)by secreting enzymes that weaken epidermal cells
D)on the piercing mouthparts of insects feeding on the plants
E)All these choices are correct.

Question 40

_____ pathogens obtain resources from living cells, whereas _____ pathogens kill cells before colonizing them.

A)Biotrophic; necrotrophic
B)Necrotrophic; biotrophic
C)All bacterial; all fungi
D)All fungi; all bacterial

Question 41

Nonprotein amino acids produced by plants:

A)are plant amino acids not incorporated into animal protein.
B)interfere with protein synthesis in herbivores.
C)are not used by plants in protein synthesis.
D)are used to produce nitrogen-rich chemical defenses such as alkaloids.

Question 42

The high silica content in grasses and the thick enamel layer on horse teeth are examples of:

A)a trade-off between growth and defense.
B)the "escape and radiate" hypothesis.
C)symbiotic co-evolution.
D)an evolutionary arms race.

Question 43

For an ecological study, you are monitoring herbivore-plant interactions in a rainforest and notice that mammalian herbivores avoid the leaves of a particular species of plant. However, a number of tiny herbivorous insect generalists that feed by piercing individual plant cells with their mouthparts appear capable of completing their entire life cycle feeding on this same species. You hypothesize that in this species the chemical defenses are:

A)stored in epidermal leaf hairs observed growing on the lower side of the leaf.
B)stored in the vacuole in an inactive form, and are activated by enzymes in the cytoplasm.
C)contained in a latex stored in vascular canals.
D)nonexistent.

Question 44

Plants can defend themselves with highly reactive compounds that cause very general toxic effects because:

A)they can sequester these compounds in specialized tissues.
B)they can store these compounds in subcellular compartments separate from their activating enzymes, so the compounds are activated only when the cell is mechanically damaged.
C)their metabolisms are so different from animals that there is no overlapping sensitivity to toxins between plants and herbivores.
D)plant cell walls form a metabolically inactive space within the plant that can store toxins without poisoning the metabolically active cytoplasm inside the cells.

Question 45

Grasses first evolved in:

A)response to the spread of large grazing mammals.
B)forested environments.
C)coevolution with herbivorous dinosaurs.
D)response to fire and or grazing by small browsers.

Question 46

Which of the following defensive compounds produced by plants can harm an herbivore's nervous system?

A)terpenes
B)alkaloids
C)tannins
D)phenols

Question 47

If a plant produces alkaloids, how will ingesting these compounds affect an herbivore?

A)The herbivore would be unable to digest certain proteins.
B)The herbivore's enzymes would be unable to function.
C)Unusable amino acids would be incorporated into the herbivore's proteins.
D)The herbivore's nervous system would be damaged.
E)The herbivore's jaws would become stuck together.

Question 48

Why do ant-plants invest in nectaries and protein/lipid food bodies on young leaves?

A)It encourages the ants to visit the plant tissues most vulnerable to herbivory.
B)It helps keep the ants away from floral nectaries, where they might attack pollinators.
C)It moves the sources of nutrition away from the parts of the plant that provide the ants' physical shelter, encouraging them to patrol the intervening stems.
D)Leaves of all plants have foliar nectaries and feeding bodies to some degree, and therefore the foliar location may not have adaptive significance.

Question 49

Chemical defenses are an important part of plant-herbivore interactions. The production of these chemical defense compounds results in an energetic cost to the organism. Which of the following statements explains how natural selection resulted in the evolution of these chemical compounds?

A)The production of chemical compounds requires nitrogen. Nitrogen used to make these compounds cannot be used to make proteins.
B)The energetic cost of producing chemical compounds is reduced because only small amounts of each chemical are needed to have their desired effects.
C)Individuals that produce chemical compounds are better protected from herbivores and are able to produce more young than individuals that do not produce the compounds.
D)Plants produce amino acids that are not incorporated into their own proteins, but herbivorous insects do incorporate these amino acids into their own proteins, rendering the herbivores' proteins nonfunctional.

Question 50

Which of the following contribute to the ability of grasses to tolerate both grazing and fire disturbances?

A)persistent zones of cell division at the leaf base
B)compressed internodes
C)silica plates
D)scattered vascular bundles in the stem

Question 51

Milkweed plants produce a variety of defenses (such as leaf hair and latex-filled canals) to deter herbivores. How can monarch caterpillars circumvent these obstacles?

A)by "mowing" hairs off of milkweed leaves
B)by cutting the midvein that transports latex through leaves
C)by creating channels to divert the flow of latex
D)by metabolizing chemical compounds (cardenolides)produced by milkweeds

Question 52

Recall that the bullhorn acacia forms a symbiosis with P. ferruginea ants. A researcher takes an acacia seed and plants it in an area without P. ferruginea. What will happen to this acacia plant?

A)It will immediately form a symbiotic relationship with ants native to the area.
B)It will begin producing alkaloids and terpenes to deter herbivores.
C)It will begin to produce hairs on its leaves to deter herbivores.
D)Without P. ferruginea, the plant won't form any new defenses and will be eaten by herbivores.

Question 53

Grass plants elevate their leaves to compete for light without exposing their shoot apical meristems to grazing animals by:

A)suppressing internode elongation between leaves.
B)growing their leaves from persistent meristematic zones at the leaf base.
C)using axillary meristems to produce leaves.
D)never elevating the shoot apical meristem.

Question 54

Nitrogen is required to synthesize which of the following defensive compounds (which are, as a result, very costly for plants to produce)?

A)alkaloids
B)menthol
C)phenols
D)nicotine
E)terpenes

Question 55

Which species of bacteria can produce the highly useful Ti plasmid, used by biologists to genetically engineer resistant crops?

A)Phytophthora infestans
B)Rhizobium radiobacter
C)Striga puccinia
D)Magnaporthe grisea
E)Xylella fastidiosa

Question 56

You may have heard that monarch butterflies (and their caterpillars) are "poisonous" to many predators. What makes these insects so toxic?

A)Monarch caterpillars produce cardenolides in their digestive tracts.
B)Monarch caterpillars use cardenolides from milkweed to synthesize toxins.
C)Monarch caterpillars ingest milkweed latex, which "chokes" their predators.
D)Monarch caterpillars store cardenolides from milkweeds.
E)Monarch caterpillars secrete latex from their bodies.

Question 57

Many physical plant defenses only work against a specific scale of herbivore-for example, spines can be too large to deter small insects, while trichomes can be too small to deter animal herbivores. Which of the following defenses deters herbivory at multiple scales by combining different modes of action?

A)silica plates in grass epidermal cells
B)alkaloid vincristine found in periwinkle
C)latex found in milkweed
D)terpene derivative pyrethrin found in chrysanthemums

Question 58

In an experiment, newly established natural plant communities containing vines, grasses, and plants that form symbiotic relations with ants ("ant-plants") are subject to one of four manipulations of the local insect popoulation, enforced by fine netting, as follows: (A) ants and herbivores present
(B) herbivores present but ants removed
(C) ants present but herbivores removed
(D) both ants and herbivores removed
After ten years, how do you expect these four manipulations will rank in terms of ant-plant biomass (high to low)?

A)A, B, C, D
B)B, C, D, A
C)C, D, A, B
D)D, A, B, C

Question 59

Plants produce a variety of defensive compounds that can seriously damage herbivores. Why aren't these compounds also detrimental to the plants themselves?

A)They can be sequestered in vacuoles of plant cells.
B)They can diffuse from leaves into the phloem of plants.
C)They are restricted to "canals" in the plant.
D)They can diffuse quickly between plant cells before they have an effect.

Question 60

Some bacteria can insert genes into the plant genome, altering the growth and metabolism of the plant in ways that enhance the bacteria's growth.

Question 61

Removing the ants from ant-plants growing in the wild would be expected to have:

A)little impact on ant-plant growth because, while loses to herbivores would increase, the plant would save the resources normally consumed by the ants.
B)a large impact on ant-plant growth, because ant-plants invest less than other plants in chemical defense, and so will be more palatable to herbivores.
C)a positive impact on ant-plant growth, because the ants in general consume more plant resources than they protect from herbivory.
D)a large impact on ant-plant growth, because the ants would not be supressing the growth of neighboring plants that compete with the ant-plants for light and nutrients.

Question 62

Which of the following is NOT true of the relationship between monarch butterflies and milkweed?

A)Monarch caterpillars are generalists that have evolved ways to metabolize the cardenolides in milkweed latex.
B)Young monarch caterpillars feed in trenches, avoiding the latex.
C)Older monarch caterpillars sever major veins and feed on resulting "safe" leaf material.
D)Monarch caterpillars are specialists that have coevolved with milkweed.
E)Monarch butterflies store cardenolides they consume and use them as a defense against predators.

Question 63

Bitter cassava is often preferred as a crop over sweet cassava because it produces higher yields (more pounds of cassava per hectare planted) in the presence of herbivores. Which of the following statements poses a hypothetical link (relationship) between the ability to make chemical deterrents and higher yields?

A)Plants produce chemicals to deter herbivores. Bitter cassava stores toxic compounds in its tissues. Bitter cassava should incur less damage, and therefore have higher yields.
B)Plants produce chemicals to deter herbivores. Bitter cassava stores toxic compounds in its roots. Because they are below ground, the roots are not eaten and the presence of toxic compounds does not contribute to higher yields.
C)Plants produce chemicals to deter herbivores. Bitter cassava expends energy producing toxic compounds. The more toxic compounds a plant produces, the lower its yields.
D)Plants produce chemicals to deter herbivores. Bitter cassava requires additional nitrogen to make these compounds. The additional nitrogen that is used reduces the amount of nitrogen available for plant growth and decreases yields.

Question 64

Some species of Acacia have coevolved with species of _____ that actively defend the plant from browsing animals and even vines.

A)beetles
B)aphids
C)ants
D)scorpions
E)biting flies

Question 65

Many phenols, such as tannins, act as antiherbivory compounds by:

A)making the inhibiting microtubule necessary for polymerization.
B)binding with proteins to reduce their digestibility.
C)binding to active sites of enzymes, preventing their function.
D)releasing unpleasant odors that deter feeding.
E)reducing animal appetite by damaging the nervous system.

Question 66

Which of the following are chemical compounds (or proteins) produced by plants that interfere with an herbivore's ability to break down proteins?

A)protease inhibitors
B)phenols
C)alkaloids
D)terpenes

Question 67

Nitrogen-bearing compounds that affect animal nervous systems and are often bitter tasting belong to which class of compounds?

A)terpenoids
B)phenols
C)alkaloids
D)latex
E)proteins

Question 68

Many plant defense compounds are used in human medicine.

Question 69

Which of the following is NOT a mechanical defense employed by plants?

A)hairs
B)silica plates
C)thorns
D)terpenes
E)spines

Question 70

Grass plants have evolved a growth form that protects _____ by keeping them close to ground level.

A)meristems
B)leaves
C)stems
D)flowers

Question 71

The dense hairs that cover the leaves of milkweed plants are an example of what type of defense?

A)chemical
B)inducible
C)phenolic
D)mechanical

Question 72

What are possible mechanisms of action for defensive compounds produced by plants?

A)to prevent premature molting in insects
B)to prevent proteins from being digested
C)to interfere with cell division
D)to interfere with an herbivore's nervous system

Question 73

Which of the following is NOT true of terpenes?

A)They are carbon-based compounds.
B)Small terpenes are easily vaporized, producing characteristic scents.
C)They are odorants that act to deter mammalian browsers.
D)They contain nitrogen in their structure.
E)Some interfere with insect development.

Question 74

The white, sticky, toxic liquid that runs through extracellular canals and is particularly common in plants of the milkweed family is called:

A)filament.
B)nectar.
C)alkaloid.
D)latex.
E)tannin.

Question 75

What methods do grasses employ to deter herbivores and survive heavy grazing?

A)Grass shoot apical meristems are located at the tips of leaves.
B)Grass shoot apical meristems remain close to the ground.
C)Grasses contain silica plates.
D)Grasses contain chitin plates.

Question 76

Alkaloids are considered "expensive" defense compounds to produce because they:

A)contain a lot of carbon, which is costly for plants to concentrate.
B)vaporize readily, so they constantly have to be synthesized.
C)contain nitrogen, an essential and often limiting element plants need.
D)often function in very small concentrations.
E)contain proteins, which are very costly for a plant to produce.

Question 77

Many grasses are adapted for grazing. One such adaptation is the positioning of their meristems high above the ground, away from hungry herbivores.

Question 78

Which of the following medicines are derived from defensive compounds originally made by plants?

A)aspirin (a pain-reliever)
B)quinine (an antimalarial drug)
C)vincristine (a chemotherapy drug)
D)taxol (a chemotherapy drug)

Question 79

Some herbivores are known as _____, feeding on a wide variety of plant species.

A)specialists
B)omnivores
C)generalists
D)autotrophs
E)carnivores

Question 80

A number of plants produce terpenes. What is one advantage that the production of terpenes has over the production of alkaloids?

A)There is no advantage because they both take energy to produce.
B)There is no advantage because terpenes are not as effective against herbivores as phenols.
C)There is an advantage because terpenes do not require nitrogen for their production.
D)There is an advantage because terpenes have a simpler chemical structure and are easier to synthesize.