Biological Science

Scott Freeman, Lizabeth Allison, Michael Black

Chapter 38

Water and Sugar Transport in Plants - all with Video Answers

Educators

Chapter Questions

Problem 1

Under what conditions does the rate of transpiration increase?
a. when the temperature of a leaf decreases
b. when stomata close at night
c. during rainstorms, when atmospheric pressure is low
d. when the weather changes and air becomes drier

Shiksha Dutta

Shiksha Dutta

Numerade Educator

Problem 2

The cells of a certain plant species can accumulate solutes to create very low solute potentials. Which of the following statements is correct?
a. The plant's transpiration rates will tend to be extremely low.
b. The plant can compete for water effectively and live in dry soils.
c. The plant will grow most effectively in soils that are saturated with water year round.
d. The plant's leaves will wilt easily.

Shiksha Dutta

Numerade Educator

Problem 3

What forces are responsible for capillarity?
a. adhesion of water molecules to the sides of xylem cells, cohesion of water molecules to each other, and surface tension
b. surface tension created by transpiration and cohesion of water molecules in a continuous flow from leaf to root c. high solute potentials created by the entry of ions during the night, when transpiration rates are low, followed by an influx of water
d. gravity and wall pressure (from the sides of xylem cells)

Shiksha Dutta

Numerade Educator

Problem 4

What is a proton pump?
a. a membrane protein that transports sucrose against a concentration gradient
b. a membrane protein that transports protons against an electrochemical gradient
c. a membrane protein that transports protons along an electrochemical gradient and sucrose against a concentration gradient
d. any membrane protein that acts as a channel-meaning it does not consume ATP

Shiksha Dutta

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Problem 5

The Casparian strip is located in what type of root cells?

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Problem 6

Proteins in sieve-tube elements must be encoded by nuclei in what cells?

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Problem 7

Why is the transport of phloem sap considered an active process?
a. The manufacture of sucrose via photosynthesis is driven by the energy in sunlight.
b. Transpiration is driven by the energy in sunlight.
c. ATP is used to transport sucrose into companion cells near sources, against a concentration gradient.
d. In spring, phloem sap moves against the force of gravity.

Shiksha Dutta

Numerade Educator

Problem 8

Draw a plant cell in pure water. Add dots to indicate solutes inside the cell. Now add dots to indicate an increase in solute potential inside the cell. Add an arrow showing the direction of water movement in response. Add arrows showing the direction of wall pressure and turgor pressure in response to water movement. Repeat the same exercise; but this time, add solutes to the solution outside the cell at a concentration that is greater than the inside of the cell.

Shiksha Dutta

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Problem 9

Compare and contrast the forces involved in transporting water in xylem via root pressure, capillarity, and transpiration. Which of these mechanisms is/are passive?

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Problem 10

Why are "cohesion-tension" and "pressure-flow" sensible names for the hypotheses analyzed in this chapter?

Shiksha Dutta

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Problem 11

How does the movement of solutes through cotransport proteins result in phloem loading?

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Problem 12

A seed is a sink when it is forming inside the parent plant. When is it a source?

Shiksha Dutta

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Problem 13

A mutant plant lacking the ability to pump protons out of leaf companion cells will be unable to do which of the following?
a. transpire from leaves
b. load sucrose into sieve cells
c. carry out photosynthesis
d. transport water through the xylem

Shiksha Dutta

Numerade Educator

Problem 14

Suppose that plants over 1 meter tall had to expend energy to transport water from their roots to their leaves. What would be the consequences in terms of growth rates and overall height?

Shiksha Dutta

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Problem 15

When young trees are transplanted to a new site, it takes several weeks or months for their root systems to grow and establish a high capacity to take up water. If a heat wave occurs during this period, the trees are likely to die-but not of starvation or loss of turgor. What kills them?

Shiksha Dutta

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Problem 16

A recent paper indicates that the aquaporins in plasma membranes of cells throughout a plant close in response to drought stress. How does the closing of these channels help plant cells maintain turgor?

Anand Jangid

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