Question 1

What drives the flow of water through the xylem?

Accepted Answer

The evaporation of water from the leaves drives the flow of water through the xylem, a process known as transpiration. As water evaporates from the leaves into the air, it creates a negative pressure that pulls more water up from the roots through the xylem. This process is also known as the transpiration-cohesion-tension mechanism.

Question 2

Rhizobia, actinomycetes, and cyanobacteria all share the common feature that they can

Accepted Answer

Rhizobia, actinomycetes, and cyanobacteria are all capable of fixing atmospheric nitrogen, converting it into a form that plants can use, which is a critical process for the nitrogen cycle in ecosystems.

Question 3

Nitrogen fixation is a process that

Accepted Answer

Nitrogen fixation is the process of converting nitrogen gas (N2) from the atmosphere into a form that can be used by plants and other organisms, such as ammonia (NH3) or nitrate (NO3-). The key process in nitrogen fixation is the conversion of N2 into ammonia (NH3) through either biological or abiotic means. This process is essential for the maintenance of life, as nitrogen is an important component of amino acids, which form the building blocks of proteins.

Question 4

Pine seedlings grown in sterile potting soil grow much slower than seedlings grown in soil from the area where the seeds were collected. This is most likely because

Accepted Answer

The slower growth of pine seedlings in sterile potting soil is likely due to the absence of normal symbiotic fungi (mycorrhizae) that aid in water and mineral uptake, which are present in the soil from the area where the seeds were collected.

Question 5

Water rises in plants primarily by cohesion-tension. Which of the following is not true about the cohesion-tension model?

Accepted Answer

The "tension" of the cohesion-tension model actually represents the negative pressure that develops inside the xylem due to transpiration. It does not represent the excitability of the xylem cells.

Question 6

Which of the following would likely not contribute to the surface area available for water absorption from the soil by a plant root system?

Accepted Answer

The endodermis is a layer of cells in the root that forms a barrier to control the movement of substances into the vascular tissue. It does not contribute to the surface area available for water absorption from the soil. The other options (root hairs, mycorrhizae, fungi associated with roots, and fibrous arrangement of roots) all increase the surface area available for water absorption by the plant root system.

Question 7

Some botanists argue that the entire plant should be considered as a single unit rather than a composite of many individual cells. Which of the following cellular structures best supports this view?

Accepted Answer

Plasmodesmata are channels that connect the cytoplasm of adjacent plant cells, allowing for the exchange of materials and the coordination of cellular activities. This interconnected network of plasmodesmata supports the idea of the entire plant being considered as a single unit, as it allows for communication and sharing of resources between cells. The other cellular structures listed, such as the cell membrane, cell wall, cytosol, and vacuole, are important for individual cell function and integrity, but do not necessarily support the view of the entire plant as a single unit.

Question 8

Most of the water taken up by a plant is

Accepted Answer

Most of the water absorbed by plants is lost to the atmosphere through the process of transpiration, which helps in cooling the plant and maintaining nutrient flow.

Question 9

Root hairs are most important to a plant because they

Accepted Answer

Root hairs are extensions of the epidermal cells in roots and increase the surface area for absorption of water and minerals from the soil. They are not responsible for anchoring the plant, storing starches, providing a habitat for nitrogen-fixing bacteria or containing xylem tissue.

Question 10

Which of the following plant structures shares the most common features and functions with a fungal hyphae?

Accepted Answer

Root hairs and fungal hyphae both have a similar function in terms of increasing surface area for absorption of nutrients and water. They also both have a thin, thread-like structure that allows them to penetrate into the surrounding substrate or soil.

Question 11

Assume that a particular chemical interferes with the establishment and maintenance of proton gradients across the membranes of plant cells. All of the following processes would be directly affected by this chemical except

Accepted Answer

Xylem transport primarily relies on physical forces such as transpiration pull and root pressure, rather than directly on proton gradients for the movement of water and minerals from roots to the rest of the plant.

Question 12

What is the main force by which most of the water within xylem vessels moves toward the top of a tree?

Accepted Answer

The main force by which most of the water within xylem vessels moves toward the top of a tree is the evaporation of water through stomata. This process, known as transpiration, creates a negative pressure in the leaf that pulls water from the roots through the xylem. This is known as the cohesion-tension theory. Root pressure (D) can help move water up in some situations, but it is not the main force responsible for water movement in tall trees.

Question 13

A plant developed a mineral deficiency after being treated with a fungicide. What is the most probable cause of the deficiency?

Accepted Answer

Mycorrhizal fungi form symbiotic relationships with plants, aiding in the absorption of minerals from the soil. The application of fungicide can kill these beneficial fungi, leading to mineral deficiencies in plants.

Question 14

Rhizobia and mycorrhizae share all of the following features except

Accepted Answer

Rhizobia and mycorrhizae are both beneficial plant-microbe interactions that enhance plant growth. They both receive carbohydrates from the plant and can be host-specific. They are also found in many ecosystems around the world. However, they do not become parasitic in nutrient-rich environments. Instead, they form mutualistic relationships with the plant, providing nutrients in exchange for carbohydrates.

Question 15

In what way do nitrogen compounds differ from other minerals needed by plants?

Accepted Answer

Nitrogen is different from other minerals needed by plants because it requires the action of bacteria to be made available to plants. Other minerals can be taken up directly from the soil by plant roots.

Question 16

Which of the following would be the most effective strategy to remove toxic heavy metals from a soil?

Accepted Answer

Adding plant species that have the ability to take up and accumulate heavy metals, known as phytoremediation, is an effective strategy for removing toxic heavy metals from soil. These plants can extract and concentrate metals from the soil in their biomass, which can then be harvested and disposed of safely.

Question 17

In plant roots, the Casparian strip is correctly described by which of the following?

Accepted Answer

The Casparian strip is a specialized region of the plant cell wall that is present in the endodermis of roots. It is composed of a layer of hydrophobic substances, such as suberin, that forms a barrier to the free diffusion of water and mineral ions. As a result, all water and dissolved substances must pass through a cell membrane before entering the stele, the central cylinder of vascular tissue in the root. This ensures that the plant can control which substances are absorbed from the soil and can avoid losing valuable mineral nutrients to the surrounding soil. Therefore, the correct description of the Casparian strip is that it ensures that all water and dissolved substances must pass through a cell membrane before entering the stele.

Question 18

Why is nitrogen fixation an essential process?

Accepted Answer

Fixed nitrogen is often the limiting factor in plant growth, meaning that without it, plants cannot grow or produce enough food for animals and humans. Nitrogen fixation is important because it converts unusable atmospheric nitrogen gas into a form that plants and other organisms can use.

Question 19

A water molecule could move all the way through a plant from soil to root to leaf to air and pass through a living cell only once. This living cell would be a part of which structure?

Accepted Answer

The endodermis is a layer of cells surrounding the root cortex and it is responsible for controlling water and mineral ion movement into the plant. The Casparian strip, a suberized band in the endodermal cell walls, prevents water and solutes from moving through the cell walls between endodermal cells, forcing them to pass through the selectively permeable plasma membranes of the endodermal cells, ensuring that all solutes pass through the selective barrier of the plasma membrane before entering the xylem. Therefore, if a water molecule only passes through a living cell once, it would only be able to pass through the endodermal cell of the root, which is why the correct answer is D.

Question 20

Transpiration in plants requires all of the following except

Accepted Answer

Transpiration in plants is the process of water movement through plant tissues and out of the plant through openings such as stomata. It is driven by adhesion of water molecules to cellulose, cohesion between water molecules, and evaporation of water molecules. Transport through tracheids is a type of xylem cell and is important for water movement in plants. However, active transport through xylem cells is not required for transpiration, as it primarily involves passive transport driven by physical forces.

Quiz 29: Resource Acquisition, Nutrition, and Transport in Vascular Plants