11 mark
Where does the majority of the water evaporate from during transpiration?
outer surface of the epidermal cell layer
the surface of the palisade mesophyll
the surface of the spongy mesophyll
inside guard cells
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Syllabus Edition
First teaching 2020
Last exams 2024
|
Transport Mechanisms (CIE AS Biology)
Exam Questions
3 hours42 questions21 mark
Which of the following processes involving transport in the xylem requires the use of ATP?
evapotranspiration from the leaves
uptake of minerals from the soil
capillary action in the xylem
osmosis of water into the xylem
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31 mark
Why might land flooded by the sea not be suitable for growing plants even after the flood water has evaporated?
not enough oxygen in the soil
too much nitrogen in the soil
too much CO2 in the soil
low water potential of soil
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41 mark
This diagram represents part of the phloem pathway, from leaf to root in a plant.
Which cell is a companion cell?
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51 mark
A student used a potometer to measure the rate of water loss from a plant by transpiration.
The internal diameter of the capillary tube and the distance moved by the bubble in fifteen seconds were recorded.
The results are shown in the table.
|
internal diameter of capillary tube / mm |
distance moved by bubble in fifteen seconds / mm |
Which calculation correctly shows how to determine the rate of transpiration in mm3 min–1?
π(1.22 x 7) x 4
π(0.62 x 7) x 4
π(1.22 x 7) / 4
π(1.2 x 7) x 4
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61 mark
Which xerophytic adaptation does not directly reduce water loss in a desert dwelling plant?
lower stomatal abundance
sunken stomata
hardened spines
epidermal hairs
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71 mark
Which is the apoplast pathway? 
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81 mark
What happens to the water potential and the hydrostatic pressure in the phloem when carbohydrate is moved into it?
| water potential | hydrostatic pressure | |
| A | increases | decreases |
| B | increases | increases |
| C | decreases | increases |
| D | decreases | decreases |
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91 mark
Which pathways in the root are blocked by the casparian strip?
1 and 2
2 and 3
1, 2 and 3
1 only
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101 mark
Which process is not responsible for the upward movement of water through the xylem?
root pressure
capillary action
transpiration pull
translocation
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11 mark
This diagram shows a transverse section of Ammophila arenaria
Which xerophytic adaptations are visible in the diagram?
1, 2 and 3
2, 3 and 4
1, 2 and 4
1, 3 and 5
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21 mark
This diagram represents part of the phloem pathway, from leaf to root in a plant.
Which process is occurring between Y and Z?
diffusion of sucrose
active transport of sucrose
diffusion of water
active transport of water
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31 mark
Why is the circumference of a tree trunk larger at night than in the middle of the day?
at night the stomata are open so there is a build-up of water in the xylem
at night the root pressure has decreased due to reduced mineral uptake by the root hair cells
at night there is less tension in the xylem vessels because the rate of transpiration is reduced
at night the sieve tube elements are full of dissolved solutes due to a reduced translocation rate
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41 mark
Which xerophytic adaptations reduce the water potential gradient?
all 5
1,2 and 4
1,4 and 5
1, 2, 3 and 5
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51 mark
A student used a potometer to measure the rate of water loss from a plant by transpiration.
The internal diameter of the capillary tube and the distance moved by the bubble in 30 seconds were recorded.
The results are shown in the table.
| internal diameter of capillary tube / mm 0.6 |
distance moved by bubble in 30 seconds / mm 14 |
What is the amount of water lost by transpiration in mm3 min-1 to 3 s.f.?
15.8
3.96
31.7
7.92
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61 mark
Sucrose and other products of photosynthesis can be moving both up and down the plant stem at the same time.
Which statement best explains how this occurs?
mass flow occurs in both directions in a phloem sieve tubes at the same time
mass flow occurs in different directions in different phloem sieve tubes at the same time
mass flow overpowers the effects of active transport
active transport moves substances up and mass flow moves substances down
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71 mark
Which feature of water is least likely to affect the climate in a tropical rainforest?
capillary action
cohesion to other water molecules
maximum density at 4oC
low viscosity
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81 mark
The rate at which water flows through xylem vessels is influenced by numerous external factors.
An increase in which factor would reduce the flow of water in the xylem?
air temperature
light intensity
wind speed
atmospheric humidity
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91 mark
Which statements about the uptake and transport of water in plants are correct?
1, 2 and 4
1, 2 and 3
2 and 3
3 and 4
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101 mark
Water absorbed by a root hair cell can travel via different pathways to reach the xylem
Which of the following best describes the route taken by water?
| apoplast pathway | symplast pathway | |
| A | always | sometimes |
| B | always | always |
| C | sometimes | always |
| D | sometimes | sometimes |
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11 mark
This diagram represents part of the phloem pathway, from leaf to root in a plant.
Which process is occurring at each stage?
| between X and Y | water potential at Z | hydrostatic pressure at T | |
| A | active transport of sucrose | lowers | decreases |
| B | active transport of sucrose | raises | increases |
| C | passive transport of sucrose | lowers | increases |
| D | passive transport of sucrose | raises | decreases |
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21 mark
Which processes are involved in transport in the phloem and xylem?
| xylem | phloem | |||||
| diffusion | mass flow | osmosis | diffusion | mass flow | osmosis | |
| A | ✓ | ✓ | X | X | ✓ | ✓ |
| B | X | ✓ | ✓ | ✓ | ✓ | X |
| C | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| D | X | X | ✓ | ✓ | ✓ | ✓ |
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31 mark
A leafy shoot was attached to a potometer and the time taken for the meniscus to move along the capillary tubing was recorded. The capillary tubing has a 0.5 mm diameter.
In one session, the student measured the bubble to be moving at a rate of 3 mm min-1
How much water would the plant absorb in 30 minutes at this rate in mm3 to two significant figures?
18
90
45
17.67
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41 mark
Which of these statements provides the best evidence that translocation occurs due to pressure-driven mass flow?
flow of sugars in phloem is 10,000x faster than diffusion alone
translocation stops in the presence of a metabolic poison that inhibits mitochondrial enzymes
positive pressure from inside the phloem forces sap out through aphid stylets (mouth parts) and this pressure lowers closer to the source
sieve tube plates allow for uninterrupted flow of solutes from source to sink
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51 mark
Which feature of xylem vessel elements allows them to stay open as transpiration increases?
the narrow lumen of the xylem vessel tubes
the absence of cross walls between xylem vessel elements
the lignification of the walls of the xylem vessel elements
the cohesion of water in the xylem vessel elements
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61 mark
Which of these statements indicates that the mass flow of sap through sieve elements is an active process?
sap in the phloem can move against the pull of gravity
sucrose is loaded into the phloem against the concentration gradient
movement of sucrose in the phloem occurs many times faster than the speed of diffusion
water enters the phloem via osmosis down a concentration gradient
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71 mark
All of these scenarios involve the movement of water by either the symplast pathway or the apoplast pathway.
Which pathway is being used in each instance?
| water moves between cells via plasmodesmata | water crosses the endodermis in the root | water passes through cell membrane into cytoplasm | water enters a plants cell wall | |
| A | apoplast | symplast | apoplast | symplast |
| B | apoplast | apoplast | symplast | symplast |
| C | symplast | symplast | symplast | apoplast |
| D | symplast | apoplast | apoplast | apoplast |
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81 mark
What determines the speed of water movement in the xylem?
the amount of water absorbed by the roots
diffusion of water through the stomata
evaporation of water from the mesophyll cells
the maintaining of a diffusion gradient in the leaves
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91 mark
Which statement best explains why the glucose produced by photosynthesis is converted into sucrose before is transported by phloem?
sucrose is a larger molecule and is more easily converted to starch
sucrose is a non-reducing sugar, so is less reactive than glucose
sucrose can pass through plant cell surface membranes more easily
sucrose is insoluble and therefore doesn’t affect water potential
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101 mark
How will the root pressure in a plant be affected by waterlogged soil?
no change
increase due to a low water potential in the soil
increase due to an increased transpiration pull
decrease due to a lack of oxygen in the soil
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