Transpiration: Lab Quiz I Answers
1. If guard cells in a plant were deficient in K+, which of the
following would be most likely to occur?
a.
b.
c.
d.
e.
Wilting would become more likely.
Photosynthesis would decrease.
Transpiration would increase.
Food transport would decrease.
A coral reef in a still lagoon
The correct response is b. Water follows the K+ into the guard
cells; if there is little K+ in the guard cells, they will lose water,
the stomata will close, and less CO2 will be available for
photosynthesis.
Refer to the illustration above to answer questions 2 - 4.
2. What tissue is indicated by label line 1?
a.
b.
c.
d.
phloem
mesophyll
epidermis
xylem
The correct response is c.
3. Which line indicates a guard cell?
a.
b.
c.
d.
e.
1
2
3
4
5
The correct answer is d.
4. Which type of cells are indicated by label line 2?
a.
b.
c.
d.
parenchyma
xylem
phloem
epidermis
The correct response is b.
5. Several factors account for the movement of water up xylem
vessels. Which single factor is most important in pulling water
toward the top of a tall tree?
a.
b.
c.
d.
Evaporation of water through stomata
Osmosis in the root
Capillary action
Atmospheric pressure
The correct response is a. It is this evaporation that provides the
transpirational pull to move water to the top of a tall tree.
6. All of the following enhance water transport in terrestrial
plants EXCEPT:
a. Hydrogen bonds linking water molecules
b. Capillary action due to adhesion of water molecules to
the walls of xylem
c. Evaporation of water from the leaves
d. K+ being transported out of the guard cells
The correct answer is d. When K+ leave the guard cells, water
follows, the guard cells become flaccid, and the stomata close.
As a result, transpiration doesn't take place.
7. Under conditions of bright light, in which part of a
transpiring plant would water potential be lowest?
a.
b.
c.
d.
Xylem vessels in the leaves
Xylem vessels in the roots
Root hairs
Spongy mesophyll of the leaves
The correct answer is d. Water moves from a region of high
water potential to a region of low water potential. The region of
lowest water potential would be at the farthest end of the
transpiration pathway.
8. What type of environment would result in the greatest rate of
transpiration?
a.
b.
c.
d.
Cloudy, humid conditions
Warm, humid conditions
Warm, light-breezy conditions
Cool, humid conditions
The correct answer is c. In breezy conditions the rate of
transpiration would be very high because of evaporative water
loss.