Question 1

How does indoleacetic acid affect fruit development?

Accepted Answer

Indoleacetic acid promotes rapid growth of the ovary, which leads to fruit development.

Question 2

Plant hormones produce their effects by

Accepted Answer

Plant hormones produce their effects by both altering the expression of genes and modifying the permeability of the plasma membrane, allowing them to influence plant growth, development, and responses to environmental stimuli.

Question 3

Why might animal hormones function differently than plant hormones?

Accepted Answer

The answer of Why might animal hormones function differently than...

Question 4

Oat seedlings are sometimes used to study auxins because

Accepted Answer

Oat seedlings are commonly used in studies involving auxins because their coleoptile (the protective sheath covering the emerging shoot) shows a strong positive phototropism, meaning it grows towards light. This characteristic makes it easier to observe and measure the effects of auxins, which are plant hormones that play a crucial role in directing plant growth towards light.

Question 5

Why do coleoptiles grow toward light?

Accepted Answer

Auxin, a plant hormone, redistributes to the shady side of the plant when exposed to light. This uneven distribution causes the cells on the darker side to elongate more than those on the light-exposed side, leading to the plant bending towards the light.

Question 6

If you were shipping green bananas to a supermarket thousands of miles away, which of the following chemicals would you want to eliminate from the plants' environment?

Accepted Answer

Ethylene is a plant hormone that promotes ripening and can cause green bananas to turn yellow and become overripe during transportation. Eliminating ethylene from the environment can extend the shelf life of the bananas and ensure they arrive at the supermarket in a fresh and edible condition.

Question 7

Which of the following plant hormones would most likely be found in high concentrations in a mature, slightly overripe fruit?

Accepted Answer

Ethylene is known to promote fruit ripening, and abscisic acid is involved in processes like fruit maturation and senescence. In overripe fruits, these hormones are typically present in higher concentrations.

Question 8

The aleurone layer is stimulated to release ________ and ________ as a result of giberrellin release from the embryo.

Accepted Answer

The aleurone layer is stimulated to release enzymes such as amylase and protease due to the action of gibberellins. Amylase breaks down starch into maltose while protease digests protein.

Question 9

According to the acid growth hypothesis, auxin works by

Accepted Answer

The acid growth hypothesis proposes that auxin causes elongation of cells by increasing the plasticity of the affected cell walls. This allows the walls to stretch, leading to cell elongation. The acid part of the hypothesis refers to the role of proton pumps in the plasma membrane that move protons (H+) out of the cell, lowering the pH in the cell wall. This acidification leads to the activation of enzymes that modify the cell wall, increasing its plasticity and allowing it to elongate.

Question 10

Auxin triggers the acidification of cell walls, which results in rapid growth, but also stimulates sustained, long-term cell elongation. What best explains how auxin brings about this dual growth response?

Accepted Answer

Auxin causes second messengers to activate both proton pumps on the plasma membrane and certain genes within the same cells, leading to both rapid growth and sustained, long-term cell elongation. Different concentrations of auxin or binding to different receptors would not explain the dual growth response. The existence of two different types of auxins or antagonistic hormones would require additional information not provided in the question.

Question 11

Which of the following field treatments would be most likely to result in a wheat or corn field with most of the plants of uniform height?

Accepted Answer

The answer of Which of the following field treatments would...

Question 12

When growing plants in culture, IAA is used to stimulate cell enlargement. Which plant growth regulator has to now be added to stimulate cell division?

Accepted Answer

Cytokinin is a plant growth regulator that stimulates cell division. While IAA promotes cell elongation and is important for cell differentiation, cytokinin is essential for cell division and also promotes shoot and root growth.

Question 13

Plant hormones can have different effects at different concentrations. This explains how

Accepted Answer

Auxin can stimulate cell elongation in apical meristems because it is produced in high concentrations in those regions. However, auxin will inhibit growth in axillary buds because it is produced in lower concentrations in those regions. This demonstrates how plant hormones can have different effects at different concentrations.

Question 14

Auxins (IAA)in plants are known to affect all of the following phenomena except

Accepted Answer

Auxins (IAA) are known to affect geotropism, phototropism, inhibition of lateral buds, and fruit development. However, maintaining dormancy is regulated by other hormones such as abscisic acid (ABA) and gibberellins (GA).

Question 15

Which of the following hormones would never be found in high concentrations in a dormant overwintering flower bud?

Accepted Answer

The answer of Which of the following hormones would never...

Question 16

Which of the following statements best summarizes the acid growth hypothesis in an actively growing shoot?

Accepted Answer

The acid growth hypothesis states that auxin activates proton pumps in the plasma membrane and tonoplast to lower the pH of the cell wall, making it more flexible by breaking bonds between cellulose microfibrils. This allows for the stretching of the cell wall and overall growth of the shoot. Option A is partially correct but does not fully explain the acid growth hypothesis. Options C, D, and E are incorrect and do not relate to the acid growth hypothesis.

Question 17

Which of the following plant hormones are most likely to act synergistically if expressed or applied to a drought-stricken plant?

Accepted Answer

Abscisic acid and ethylene are both involved in regulating water stress responses in plants. Abscisic acid helps plants conserve water by closing stomata while ethylene stimulates the production of proteins that protect against drought. Therefore, the two hormones are likely to act synergistically to help a drought-stricken plant.

Question 18

If a farmer wanted more loosely packed clusters of grapes, he would most likely spray the immature bunches with

Accepted Answer

Gibberellins promote cell elongation and division, which would result in less tightly packed grape clusters. Auxin, cytokinins, abscisic acid, and ethylene are unlikely to have the same effect on grape clusters.

Question 19

Which of the following hormones would be most useful in promoting the rooting of plant cuttings?

Accepted Answer

Auxins are hormones that stimulate cell elongation and differentiation, making them the most useful hormone in promoting the rooting of plant cuttings.

Question 20

Which of the following statements applies to plant growth regulators?

Accepted Answer

Plant growth regulators often have a multiplicity of effects, meaning they can affect multiple aspects of plant growth and development, such as cell division, elongation, differentiation, and gene expression.

Quiz 39: Plant Responses to Internal and External Signals