Chapter 35: Water and Sugar Transport in Plants Practice Test

Which of the following allows plants to be selective about the molecules that enter the xylem?

A waxy barrier in the plant root.

Based on Ernst Münch's pressure-flow hypothesis, which conditions would increase the rate of translocation within the phloem?

An increase in sucrose production at the source

What characterizes the rates of photosynthesis and transport in a plant on a dry cloudy day?

Both the photosynthesis and transpiration rates are low

What role does cohesion play in the process of water movement from roots to leaves?

Cohesion causes the column of water to act as a continuous chain.

Which of the following terms describes water molecules sticking to other water molecules?

Cohesion.

Which cell layer filters water and solutes moving into or out of the vascular tissue of the roots?

Endodermis

Which tissue acts as a filter on the water absorbed by root hairs?

Endodermis

True or false? Root pressure can move water a long distance up the xylem because of the higher water potential of the xylem in comparison to the water potential in the surrounding cells.

False

True or false? The rate of sugar transport in a plant depends on the rate of photosynthesis, the rate of transpiration, and the difference in turgor pressure between the source and the sink.

False

Which of the following best describes the movement of food through the phloem?

From mature leaves to roots and seeds

Which structure is necessary for the symplastic pathway of water transport in a plant?

Plasmodesmata

What causes guttation?

Positive pressure in the root xylem and a decreased rate of transpiration at night

Loading sucrose into the phloem at a source requires the plant to expend energy. How is sucrose loaded into the phloem against its concentration gradient?

Protons are pumped out of the cell through proteins. They diffuse back into the cell through cotransporters, which allow sucrose through at the same time.

Which of the following describes the correct order in which water moves through a plant and into the atmosphere?

Root, xylem, leaf cells, air space inside leaves, outside air.

To test the effects of soil moisture on spruce tree physiology, you measure the water potential of branches taken from two sets of identical trees: Set A is well watered and set B is poorly watered. Which data set represents reasonable results from this experiment?

Set A: ¯0.7 MPa; set B: ¯2.1 MPa

Which term describes an area where sugars are used or stored?

Sink

After leaving a vegetable relish tray out for several hours, you find that the celery sticks are no longer crisp. How could you treat the celery to correct the situation?

Soak them in cool water.

An animal cell and a plant cell are placed in a highly hypotonic solution. What will happen?

The animal cell will burst.

Scientists subjected a corn plant to different light intensities while measuring the xylem pressure in the leaves. They found that the brighter the light, the more negative the pressure in the xylem. Which of the following is the best interpretation of these results?

The increased light intensity increased the rate of transpiration, which increased the tension within the xylem.

What happens when the plant loses water faster than it is able to replace it?

The leaves wilt.

Which of the following statements about the distribution of sap throughout a plant is true?

The mechanism that explains the movement of sugars throughout a plant is called the pressure-flow hypothesis.

Plants that live in dry environments have several structural features that allow them to conserve water. Which set of characteristics best describes plants that live in a dry environment?

Thick cuticle; sunken stomata surrounded by hairs

Food made at a source is translocated to nearby sinks that are often on the same side of the plant. Why does this happen?

Vascular tissue in the leaf and stem is organized into discrete bundles that run the length of the organ.

Which of the following statements about xylem transport is true?

Water and minerals move through the root cortex into the xylem and upward through the stem and into leaves.

If we start with a cell that is in osmotic equilibrium with its surroundings, what would be the effect of increasing the solute concentration outside the cell?

Water would flow from the cell to the outside environment.

Do aquatic plants still need a vascular system?

Yes, they need it to move sugars.

Why is phloem unloading passive in young leaves, but active in roots of a sugar beet plant?

Young leaves immediately use unloaded sucrose, creating a concentration gradient. Sucrose builds up in storage cells of sugar beet roots.

What is the difference between adhesion and cohesion? Give examples of each in plant water transport.

cohesion: water molecules stick to each other ex. water sticking to eachother in xylem adhesion: water molecules stick to other molecules and water ex. water sticking to fibers in plant cell wall

The function of a root hair is to

increase the surface area available for absorption in plant roots.

The loss of water from plants through transpiration

is an important part of the mechanism that pulls water from a plant's roots to its leaves.

What is the transpiration-cohesion-tension mechanism? How does this mechanism explain how water and soil nutrients move from the roots of a plant to its leaves?

negative force (pull) generated at air-water interfaces is transmitted outside leaf cells to water in xylem to the water in vascular tissue of roots and to the water of the roots.

Transport of water through the xylem is _____.

passive, requiring no energy expenditure by the plant

What is waxy barriers in the root role involved with water transport of a plant?

prevent molecules from entering xylem directly

The cohesion-tension theory of water movement in the xylem states that water, as it evaporates through the stomata, pulls additional water from the xylem due to water's cohesive nature. The resulting tension in the xylem _____.

pulls more water up from the roots

What are root hairs role involved with water transport of a plant?

root hairs increase surface area available for absorption

What is xylem involved with water transport of a plant?

transports water and soil nutrients from the roots to the rest of the plant. *part of vascular system *composed of dead cells

What are the small pores in the leaves role involved with water transport of a plant?

water diffuses from air spaces inside leaves through the pores. this process is called transpiration

Transpiration is best defined as _____.

water loss from aerial plant parts

What is transpiration

water loss from plants through evaporation

What are roots role involved with water transport of a plant?

water moves into roots