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Chapter 36



Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
 

 1. 

Which of the following is true concerning the water potential of a plant cell?
a.
It is higher than that of air.
b.
It is equal to zero when the cell is in pure water and is turgid.
c.
It is equal to 0.23 MPa.
d.
It becomes higher when K+ is actively moved into the cell.
e.
It becomes lower after the uptake of water by osmosis.
 

 2. 

The value for chpt36_files/i0030000.jpg in root tissue was found to be -0.15 MPa. If you take the root tissue and place it in a 0.1 M solution of sucrose (chpt36_files/i0030001.jpg = -0.23), net water flow would
a.
be from the tissue into the sucrose solution.
b.
be from the sucrose solution into the tissue.
c.
be in both directions and the concentrations would remain equal.
d.
occur only as ATP was hydrolyzed in the tissue.
e.
be impossible to determine from the values given here.
 

 3. 

Which of the following would likely not contribute to the surface area available for water absorption from the soil by a plant root system?
a.
root hairs
b.
endodermis
c.
mycorrhizae
d.
fungi associated with the roots
e.
fibrous arrangement of the roots
 

 4. 

All of the following describe an important component of the long-distance transport process in plants except
a.
cohesion-tension-transpiration.
b.
osmosis.
c.
endodermis Casparian strip.
d.
active transport.
e.
bulk flow from source to sink.
 

 5. 

The following factors may sometimes play a role in the movement of sap through xylem. Which one depends on the direct expenditure of ATP by the plant?
a.
capillarity of water within the xylem
b.
evaporation of water from leaves
c.
cohesion among water molecules
d.
concentration of ions in the symplast
e.
bulk flow of water in the root apoplast
 

 6. 

What is the main force by which most of the water within xylem vessels moves toward the top of a tree?
a.
active transport of ions into the stele
b.
atmospheric pressure on roots
c.
evaporation of water through stoma
d.
the force of root pressure
e.
osmosis in the root
 

 7. 

Water potential is generally most negative in which of the following parts of a plant?
a.
mesophyll cells of the leaf
b.
xylem vessels in leaves
c.
xylem vessels in roots
d.
cells of the root cortex
e.
root hairs
 

 8. 

Which of the following statements is false concerning the xylem?
a.
Xylem tracheids and vessels fulfill their vital function only after their death.
b.
The cell walls of the tracheids are greatly strengthened with cellulose fibrils forming thickened rings or spirals.
c.
Water molecules are transpired from the cells of the leaves, and replaced by water molecules in the xylem pulled up from the roots due to the cohesion of water molecules.
d.
Movement of materials is by mass flow; materials move owing to a turgor pressure gradient from "source" to "sink."
e.
In the morning, sap in the xylem begins to move first in the twigs of the upper portion of the tree, and later in the lower trunk.
 

 9. 

Guard cells do which of the following?
a.
protect the endodermis
b.
accumulate K+ and close the stomata
c.
contain chloroplasts that import K+ directly into the cells
d.
guard against mineral loss through the stomata
e.
help balance the photosynthesis-transpiration compromise
 

 10. 

All of the following normally enter the plant through the roots except
a.
carbon dioxide.
b.
nitrogen.
c.
potassium.
d.
water.
e.
calcium.
 

 11. 

Guard cells are the only cells in the epidermis that contain chloroplasts and can undergo photosynthesis. This is important because
a.
chloroplasts sense when light is available so that guard cells will open.
b.
photosynthesis provides the energy necessary for contractile proteins to flex and open the guard cells.
c.
guard cells will produce the O2 necessary to power active transport.
d.
ATP is required to power proton pumps in the guard cell membranes.
e.
both A and C
 

 12. 

Which of the following is a correct statement about sugar movement in phloem?
a.
Diffusion can account for the observed rates of transport.
b.
Movement can occur both upward and downward in the plant.
c.
Sugar is translocated from sinks to sources.
d.
Only phloem cells with nuclei can perform sugar movement.
e.
Sugar transport does not require energy.
 

 13. 

Phloem transport is described as being from source to sink. Which of the following would most accurately complete this statement about phloem transport as applied to most plants in the late spring? Phloem transports ____ from the ____ source to the ____ sink.
a.
amino acids; root; mycorrhizae
b.
sugars; leaf; apical meristem
c.
nucleic acids; flower; root
d.
proteins; root; leaf
e.
sugars; stem; root
 



 
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