Structure And Function Of Plants

2.

Which of the following processes is responsible for the bending of the stem of a plant toward a light source?

The amount of chlorophyll produced on the side facing the light increases.
The rate of cell division on the side facing the light increases.
The rate of cell division on the side away from the light increases.
The cells on the side of the stem away from the light elongate.

Correct Answer

A. The cells on the side of the stem away from the light elongate.

Explanation

When a plant stem bends towards a light source, it is due to a process called phototropism. Phototropism is the growth or movement of a plant in response to light. In this case, the cells on the side of the stem away from the light elongate, causing the stem to bend towards the light. This elongation of cells is a result of an uneven distribution of auxin, a hormone that regulates plant growth. The side of the stem away from the light receives more auxin, which stimulates cell elongation and causes the bending towards the light source.

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3.

The driving force for the movement of materials in the xylem of plants is

Gravity
Root pressure
Transpiration
Osmosis

Correct Answer

A. Transpiration

Explanation

Transpiration is the process by which water is evaporated from the leaves of plants. This creates a negative pressure or tension in the xylem, causing water to be pulled up from the roots to the leaves. This upward movement of water, along with dissolved minerals, is known as the transpiration pull. Therefore, transpiration is the driving force for the movement of materials in the xylem of plants.

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4.

Hydrogen bonding plays a particularly important role in which plant process?

Pressure-flow hypothesis
Mutualistic relationships
Attraction of the sperm and egg.
The transpiration-cohesion-tension mechanism

Correct Answer

A. The transpiration-cohesion-tension mechanism

Explanation

The transpiration-cohesion-tension mechanism is a plant process that relies on the cohesive properties of water and the tension created by transpiration to transport water and nutrients from the roots to the leaves. Hydrogen bonding between water molecules is a crucial component of this mechanism as it allows for the cohesion of water molecules, enabling them to be pulled up through the plant's xylem vessels against gravity. Therefore, hydrogen bonding plays a particularly important role in the transpiration-cohesion-tension mechanism.

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5.

Act with auxins to promote cell division and differentiation:

Abscisic acid
Auxin
Cytokinins
Ethylene
Gibberellins

Correct Answer

A. Cytokinins

Explanation

Cytokinins act with auxins to promote cell division and differentiation. Cytokinins are a class of plant hormones that regulate cell division and growth. They work in conjunction with auxins, another class of plant hormones, to stimulate cell division and promote the development of specialized cells. This interaction between cytokinins and auxins is essential for proper plant growth and development.

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6.

Primary hormone involved with phototropism and gravitropism:

Abscisic acid
Auxin
Cytokinins
Ethylene
Gibberellins

Correct Answer

A. Auxin

Explanation

Auxin is the primary hormone involved in both phototropism and gravitropism. Phototropism is the growth or movement of a plant in response to light, and auxin helps to regulate this process by promoting elongation of cells on the shaded side of the plant, causing it to bend towards the light source. Gravitropism is the growth or movement of a plant in response to gravity, and auxin also plays a crucial role in this process by redistributing within the plant to cause differential growth rates, resulting in either upward or downward bending of the plant.

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7.

This hormone is lacking in dwarf varieties of plants:

Abscisic acid
Auxin
Cytokinins
Ethylene
Gibberellins

Correct Answer

A. Gibberellins

Explanation

Gibberellins are a group of hormones that promote plant growth and development. They are responsible for regulating various processes such as stem elongation, seed germination, and flowering. In dwarf varieties of plants, there is a deficiency of gibberellins, which leads to stunted growth and shorter stems. This hormone is crucial for the normal growth and development of plants, and its absence in dwarf varieties is the reason behind their reduced size.

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8.

Inhibits growth; closes stomata during drought:

Abscisic acid
Auxin
Cytokinins
Ethylene
Gibberellins

Correct Answer

A. Abscisic acid

Explanation

Abscisic acid is the correct answer because it is a plant hormone that inhibits growth and plays a role in closing stomata during drought. Stomata are small openings on the surface of leaves that allow for gas exchange, including water vapor. During drought conditions, plants need to conserve water, so abscisic acid is produced to close the stomata and reduce water loss through transpiration. This hormone also inhibits cell division and growth, helping the plant to conserve energy and resources during periods of water scarcity.

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9.

This hormone is used at high concentrations as an herbicide:

Abscisic acid
Auxin
Cytokinins
Ethylene
Gibberellins

Correct Answer

A. Auxin

Explanation

Auxin is a hormone that is commonly used as an herbicide at high concentrations. It is a plant growth regulator that controls various aspects of plant development, including cell elongation and root formation. When applied in high concentrations, auxin disrupts the normal growth patterns of plants, leading to stunted growth and ultimately killing the plant. This makes it an effective herbicide for controlling unwanted plant growth in agricultural and horticultural settings.

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10.

In plants, translocation occurs as a result of

A difference in water potential between a sugar source and a sugar sink.
Transpiration
Cohesion-adhesion
Active transport by sieve-tube members

Correct Answer

A. A difference in water potential between a sugar source and a sugar sink.

Explanation

Translocation in plants refers to the movement of sugars from the source (where they are produced, such as leaves) to the sink (where they are utilized, such as roots or fruits). This movement occurs due to a difference in water potential between the sugar source and sugar sink. Water potential is affected by the concentration of solutes, including sugars. The higher concentration of sugars in the source creates a lower water potential, causing water to move from the sugar sink to the sugar source. This creates a pressure gradient that allows the sugars to be transported through the phloem.

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Structure And Function Of Plants

Which of the following is primarily responsible for fruit ripening in plants?

Quiz Preview

Which of the following processes is responsible for the bending of the stem of a plant toward a light source?

The driving force for the movement of materials in the xylem of plants is

Hydrogen bonding plays a particularly important role in which plant process?

Act with auxins to promote cell division and differentiation:

Primary hormone involved with phototropism and gravitropism:

This hormone is lacking in dwarf varieties of plants:

Inhibits growth; closes stomata during drought:

This hormone is used at high concentrations as an herbicide:

In plants, translocation occurs as a result of