Question 1

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?

Accepted Answer

Gibberellin needs to bind to a receptor and initiate a signal transduction cascade that activates a transcription factor, which in turn triggers the transcription of the Myb gene. This process takes time and explains why the Myb mRNA was not detectable until 6-12 hours after gibberellin application.

Question 2

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?

Accepted Answer

The answer of Plant A is diploid and is homozygous...

Question 3

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?

Accepted Answer

The answer of A particular species of virus carries a...

Question 4

What do phototropin and ABA have in common?

Accepted Answer

The answer of What do phototropin and ABA have in...

Question 5

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

Accepted Answer

The presence of black, dead spots on the leaves indicates that the plant has been invaded by a pathogen. The plant's response to this invasion would be a hypersensitive response, which involves programmed cell death in the infected area to prevent the spread of the pathogen. A, B, D, and E are all incorrect choices. Avirulence, resistance, and virulence are terms used to describe characteristics of the pathogen, not the plant's response.

Question 6

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

Accepted Answer

The experiments suggest that ethylene stimulates growth in tobacco plants when they are exposed to far-red light, which is part of the shade avoidance response. This is supported by the observation that exposure to both far-red light and small concentrations of ethylene leads to greater increases in stem length, petiole length, and petiole angle. Additionally, mutant plants that are insensitive to ethylene do not show a shade avoidance response when exposed to far-red light, indicating that ethylene is necessary for this response. Therefore, choice B, "stimulates growth when tobacco plants are shaded by other plants," is the best choice.

Question 7

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?

Accepted Answer

A mutation in the bacterial avirulence gene that prevents the avirulence factor from binding to the plant's resistance factor would prevent the plant from detecting the bacterium and thus allow for successful colonization.

Question 8

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?

Accepted Answer

The answer of In the fall,the leaves of some trees...

Question 9

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?

Accepted Answer

Salicylic acid is a hormone that plays a key role in plant defense against pathogenic bacteria and viruses. Manipulating the levels of salicylic acid in a plant can increase its resistance to these attacks.

Question 10

Based on the findings presented above,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.

Accepted Answer

1) The R protein binds to the avr protein (recognition of pathogen)
2) The pathogen releases avr proteins.
5) A signal transduction cascade occurs (activation of defense genes)
8) The plant cell produces both nitric oxide and reactive oxygen intermediates (defense response)
6) The plant cell and the pathogen die (hypersensitive response)
Therefore, the correct sequence of events is 2, 1, 5, 8, and 6. Option B matches this sequence.

Question 11

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?

Accepted Answer

Farmers would be interested in buying this chemical to spray on fruit after picking to stall ripening. This would allow them to transport and sell the fruit over a longer period of time without it becoming overripe or spoiled.

Question 12

Why would the researchers study the association between cell death,nitric oxide,and reactive oxygen intermediates?

Accepted Answer

The association between cell death, nitric oxide, and reactive oxygen intermediates is relevant to understanding what happens after R-avr protein binding. This study can help gain insight into how the plant responds to pathogen attack and how it activates defense mechanisms to prevent further infection.

Question 13

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

Abscisic acid (ABA) is known for its role in plant response to drought stress. It regulates stomatal closure, plant water status, and gene expression involved in stress response. Higher levels of ABA can help plants to survive in drought conditions by reducing water loss through stomata, inducing root growth, and increasing osmotic adjustment. Therefore, it is likely that the survivors have the ability to synthesize higher levels of ABA than their siblings do.

Question 14

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?

Accepted Answer

All of the choices listed, proteinase inhibitors, systemin, and jasmonic acid, are involved in a plant's defense mechanisms against herbivores or pests. Proteinase inhibitors disrupt the digestive processes of the herbivore, systemin is a signaling molecule that activates defense genes, and jasmonic acid is involved in signaling pathways that lead to the production of defense compounds.

Question 15

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?

Accepted Answer

Systemic acquired resistance (SAR) is a process by which a plant can defend against a wide range of pathogens after being exposed to a triggering infection. This defense mechanism involves the production of compounds that can inhibit the growth and spread of invading pathogens, as well as activate other defense responses within the plant. Once SAR is induced, the plant becomes less susceptible to subsequent infections by the same or different pathogens. Therefore, the plant's ability to prevent infection of the roots by the same bacterial species that infected the leaves is likely due to SAR.

Question 16

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.

Accepted Answer

The bacterium would be more effective at infecting plant cells because breaking down reactive oxygen intermediates and inhibiting nitric oxide production would help it evade the plant's defense mechanisms.

Question 17

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

Accepted Answer

Heterozygosity for a gene that binds plant pheromones would allow the parasitoid to respond to signals from multiple plants. It is not necessarily related to the parasitoid's ability to infect plants or insects.

Question 18

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?

Accepted Answer

Overripe fruit releases ethylene, which accelerates the ripening process in other fruits. By putting the fresh fruit in the same crisper as the overripe fruit, the fresh fruit was exposed to the ethylene released by the overripe fruit, causing it to ripen quickly and become overripe as well.

Question 19

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?

Accepted Answer

The answer of You have discovered a previously unidentified plant,and...

Question 20

What do abscisic acid and gibberellins have in common?

Accepted Answer

The answer of What do abscisic acid and gibberellins have...

Quiz 39: Plant Sensory Systems, signals, and Responses