Question 1

The "wall-loosening factor" present in the cell wall of plants is now believed to be

Accepted Answer

Acid-activated expansins are responsible for loosening the cell wall in plants. They break the hydrogen bonds between cellulose microfibrils and other wall constituents, allowing the cell to expand and grow.

Question 2

Which of the following is not involved in the acid growth hypothesis for the regulation of cell expansion by auxin?

Accepted Answer

The acid growth hypothesis involves the pumping of protons (H+) into the apoplast, not into the cytosol. This acidification of the cell wall region activates enzymes that loosen the cell wall, allowing for cell expansion.

Question 3

Refer to the figure below.  Both sets of tomatoes were picked before ripening.The tomatoes on the right are red, while those on the left are still green, because

Accepted Answer

The red tomatoes have been treated with ethylene, which is a gaseous plant hormone that promotes ripening of fruits. Ethylene is commonly used in the agriculture industry to accelerate the ripening of fruits, including tomatoes. The green tomatoes on the left have not been treated with ethylene, which is why they have not ripened yet.

Question 4

Radishes provide a good demonstration of the pronounced swelling that cytokinins can cause in

Accepted Answer

Radishes are root vegetables and cytokinins are known to cause pronounced swelling in root tissues.

Question 5

If a mutant plant were created that lacked the receptor for ethylene, its leaves would

Accepted Answer

Abscission is the process of shedding leaves, flowers or fruits. Ethylene plays a crucial role in the abscission process, and without the receptor for ethylene, the plant would be unable to undergo abscission in the fall. Other choices are not directly related to the function of the ethylene receptor.

Question 6

Florists use silver thiosulfate to

Accepted Answer

Silver thiosulfate is used to inhibit the action of ethylene, which is responsible for causing petals to turn brown and fall off.

Question 7

An unripe lemon that is placed in a paper bag with an apple will ripen; its skin will yellow, it will soften, and it will produce the characteristic lemon odor.Which plant hormone released by the apple causes this effect?

Accepted Answer

Ethylene is the plant hormone that promotes fruit ripening and is released by apples. When an unripe lemon is kept in a paper bag with an apple, the apple releases ethylene which triggers the ripening process in the lemon. The ripening process includes yellowing of the skin, softening of the fruit, and the production of the characteristic lemon odor. Auxin, cytokinins, gibberellins, and abscisic acid are not involved in the ripening process.

Question 8

Refer to the figure below.Each pair includes a dwarf plant with a hormonal deficiency and a normal-sized plant of the same species.  By comparing the plants within the same species and then making comparisons between species, you would find that plant hormones

Accepted Answer

By comparing the normal-sized and dwarf plants within the same species, we can observe the effects of the hormonal deficiency. By comparing the same hormonal deficiency in different species, we can see that the deficiency can have the same general effects. Therefore, plant hormones can have the same general effects in different species.

Question 9

Refer to the figure below.  The leaf on the left is turning yellow because it is experiencing a natural process known as

Accepted Answer

The yellowing of a leaf is a sign of senescence, which is the natural process of aging and death in plants. Choices A and B refer to growth and development processes, while choices C and D refer to periods of dormancy or lack of growth.

Question 10

What is the difference between the cytokinins kinetin and zeatin?

Accepted Answer

Zeatin is an endogenous cytokinin, naturally occurring in plants and kinetin is a synthetic cytokinin. They both play similar roles in plant growth and development, but their chemical structures differ.

Question 11

A researcher who wishes to experimentally manipulate leaf senescence in tobacco would apply _______ to promote senescence and _______ to delay it.

Accepted Answer

Ethylene is known to promote leaf senescence in plants, so the researcher would apply ethylene to promote senescence. On the other hand, auxin is known to delay leaf senescence, so the researcher would apply auxin to delay it.

Question 12

Refer to the figure below showing a signal reception pathway.  Predict what is most likely to happen when the relevant hormone (e.g., auxin or gibberellin) is present.

Accepted Answer

When the relevant hormone (e.g., auxin or gibberellin) is present, it is most likely that the plant will grow taller. This is because the signal reception pathway involves the hormone binding to a receptor and initiating a cascade of events that ultimately leads to cell elongation and growth.

Question 13

Refer to the figure below showing a signal reception pathway.  A mutant plant with an inactive form of the repressor protein (for auxin or gibberellin) is compared to a typical plant.Predict the results of this experiment.

Accepted Answer

The repressor protein usually inhibits the transcription of growth-promoting genes in the absence of the relevant hormone. In the mutant plant with an inactive form of the repressor protein, the transcription of these genes is not inhibited even in the absence of the relevant hormone, leading to increased growth and development.

Question 14

A homeowner has set up an outdoor gas-burning grill next to her favorite camellia bush.After the first few nights of using the grill, she notices that the camellia is beginning to lose its leaves.Which statement best explains what is happening?

Accepted Answer

Ethylene is a gas that is released during the burning of gas, and it has been shown to cause leaf drop and other symptoms of senescence in plants. The proximity of the grill to the camellia bush is likely causing exposure to higher levels of ethylene, which is causing the plant to lose its leaves.

Question 15

Unlike other plant hormones, ethylene

Accepted Answer

Ethylene is a gas and is considered a unique plant hormone because it acts as both an inhibitor and a promoter in various plant processes. It is not produced by all plants but can have a significant impact on fruit ripening, senescence, and other developmental processes in those that do produce it.

Question 16

Which cell-division promoting plant hormone is structurally related to a base common in nucleic acids?

Accepted Answer

Zeatin is a cytokinin that promotes cell division in plants and is structurally related to adenine, a base common in nucleic acids.

Question 17

Refer to the figure below.  The leaf on the right is green and healthy because

Accepted Answer

The answer of Refer to the figure below.  The...

Question 18

Auxin's polar transport relies in part on the fact that auxin is a weak acid that

Accepted Answer

Auxin is a weak acid that ionizes to release positively charged ions (H^{+) and negatively charged ions (}-) in neutral pH conditions. This ionization allows for polar transport of auxin as the negatively charged ions can move towards the positively charged end of the cell, while the positively charged ions can move towards the negatively charged end of the cell. This transport is facilitated by specialized proteins, such as PIN proteins.

Question 19

Refer to the figure below showing a signal reception pathway.  What happens when the relevant hormone (e.g., auxin or gibberellin) is absent?

Accepted Answer

The answer of Refer to the figure below showing a...

Question 20

Which plant hormone stimulates axillary buds to grow into branches?

Accepted Answer

Cytokinin promotes cell division and is known to stimulate the growth of axillary buds into branches, counteracting the apical dominance induced by auxin.

Quiz 36: Regulation of Plant Growth

The "wall-loosening factor" present in the cell wall of plants is now believed to be

Which of the following is not involved in the acid growth hypothesis for the regulation of cell expansion by auxin?

Refer to the figure below. Both sets of tomatoes were picked before ripening.The tomatoes on the right are red, while those on the left are still green, because

Radishes provide a good demonstration of the pronounced swelling that cytokinins can cause in

If a mutant plant were created that lacked the receptor for ethylene, its leaves would

Florists use silver thiosulfate to

An unripe lemon that is placed in a paper bag with an apple will ripen; its skin will yellow, it will soften, and it will produce the characteristic lemon odor.Which plant hormone released by the apple causes this effect?

Refer to the figure below.Each pair includes a dwarf plant with a hormonal deficiency and a normal-sized plant of the same species. By comparing the plants within the same species and then making comparisons between species, you would find that plant hormones

Refer to the figure below. The leaf on the left is turning yellow because it is experiencing a natural process known as

What is the difference between the cytokinins kinetin and zeatin?

A researcher who wishes to experimentally manipulate leaf senescence in tobacco would apply _ to promote senescence and _ to delay it.

Refer to the figure below showing a signal reception pathway. Predict what is most likely to happen when the relevant hormone (e.g., auxin or gibberellin) is present.

Refer to the figure below showing a signal reception pathway. A mutant plant with an inactive form of the repressor protein (for auxin or gibberellin) is compared to a typical plant.Predict the results of this experiment.

A homeowner has set up an outdoor gas-burning grill next to her favorite camellia bush.After the first few nights of using the grill, she notices that the camellia is beginning to lose its leaves.Which statement best explains what is happening?

Unlike other plant hormones, ethylene

Which cell-division promoting plant hormone is structurally related to a base common in nucleic acids?

Refer to the figure below. The leaf on the right is green and healthy because

Auxin's polar transport relies in part on the fact that auxin is a weak acid that

Refer to the figure below showing a signal reception pathway. What happens when the relevant hormone (e.g., auxin or gibberellin) is absent?

Which plant hormone stimulates axillary buds to grow into branches?