Question 1

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 stimulates cell division and is often used in combination with IAA to promote overall plant growth.

Question 2

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

Accepted Answer

The acid growth hypothesis proposes that auxin-activated proton pumps lower the pH of the cell wall, which breaks bonds and makes the cell wall more flexible. This allows for cell expansion and growth. It is not the case that auxins stimulate proton pumps in the plasma membrane and tonoplast (A), that auxins and gibberellins act as a lubricant (C), that auxins activate aquaporins (D), or that auxins and gibberellins are transported to vacuoles to build up turgor pressure (E).

Question 3

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

Accepted Answer

Auxins are known to promote cell elongation and can induce the formation of roots on stem cuttings. They are commonly used in horticulture to facilitate the production of new plants from cuttings.

Question 4

Why might animal hormones function differently than plant hormones?

Accepted Answer

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

Question 5

The plant hormone involved in aging and ripening of fruit is

Accepted Answer

Ethylene is the plant hormone responsible for the aging and ripening of fruit. It is produced naturally by the fruit as it ripens and can also be produced artificially to stimulate ripening.

Question 6

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.

Question 7

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

Accepted Answer

The statement "Plant hormones can have different effects at different concentrations" explains how auxin can stimulate cell elongation in apical meristems, yet will inhibit the growth of axillary buds. This is an example of how a hormone can have different effects at different concentrations.

Question 8

According to the acid growth hypothesis,auxin works by

Accepted Answer

According to the acid growth hypothesis, auxin helps to increase wall plasticity and allows for the affected cell walls to elongate. This occurs through acidification of the cell wall, which activates enzymes that break down the wall, allowing for expansion and growth.

Question 9

Which of the following plant hormones would be found in very low amounts in a mature,water-stressed tomato plant?

Accepted Answer

Gibberellins, cytokinins, and auxins are growth-promoting hormones that would be found in lower amounts in a mature, water-stressed tomato plant. Water stress typically leads to an increase in abscisic acid, which inhibits growth and promotes stomatal closure to reduce water loss.

Question 10

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 11

Which plant hormones would likely be found in high amounts in a sprouting vegetative stem?

Accepted Answer

Auxins, gibberellins, and cytokinins are all involved in the regulation of cell elongation and growth, which is a characteristic of a sprouting vegetative stem. Gibberellins and cytokinins also promote overall plant growth and development.

Question 12

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 various aspects of plant growth and development. They can affect cell division, elongation, differentiation, and other physiological processes. Additionally, they can interact with other hormones and signaling pathways in the plant.

Question 13

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

Accepted Answer

Auxins are known to affect geotropism, phototropism, inhibition of lateral buds, and fruit development in plants. However, they do not have a significant effect on the maintenance of dormancy. Other plant hormones such as abscisic acid and cytokinins play a more significant role in regulating dormancy.

Question 14

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 15

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

Accepted Answer

Both abscisic acid and ethylene have been shown to play critical roles in plant responses to drought stress. While abscisic acid is known to regulate stomatal closure, reduce transpiration and promote root growth, ethylene regulates plant growth and development, and also helps plants to withstand environmental stresses, including drought. Therefore, the expression or application of both hormones could work synergistically to help the plant survive drought conditions.

Question 16

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 can lead to looser bunches of grapes.

Question 17

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

Accepted Answer

The answer of Which of the following plant hormones would...

Question 18

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 19

Plant hormones produce their effects by

Accepted Answer

Plant hormones can affect gene expression by binding to specific receptors and activating signaling pathways that ultimately result in changes in gene expression. They can also modify the permeability of the plasma membrane, allowing for the entry of specific ions or molecules that may be necessary for certain physiological processes. Therefore, both altering the expression of genes and modifying plasma membrane permeability are important mechanisms by which plant hormones produce their effects. However, there is no evidence to support the idea that plant hormones modify the structure of the nuclear envelope membrane. Therefore, the best choice is (D) altering the expression of genes and modifying the permeability of the plasma membrane.

Question 20

How does indoleacetic acid affect fruit development?

Accepted Answer

Indoleacetic acid (IAA) is a type of plant growth hormone that promotes cell elongation and rapid growth. When IAA levels are high in the ovary tissue of a flower, it can stimulate the cells to grow rapidly and form the fruit. This is particularly important in the early stages of fruit development when the ovary is rapidly expanding. Therefore, IAA promotes rapid growth of the ovary, leading to fruit development.

Quiz 39: Plant Responses to Internal and External Signals