Exam code: H420
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Water and dissolved minerals are transported by the water-conducting tissues in plants.
Which of the following is primarily responsible for the transport of water and minerals from the roots to the topmost shoot of the plant?
Companion cells
Vascular tissues
Sieve tube elements
Vessel elements
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Water and dissolved solutes move through different pathways in plants.
Which of the following statements, correctly describes the apoplastic pathway for the movement of water?
1 | Water moves by diffusion through the cellulose cell walls, dead cells and, the hollow tubes of the xylem |
2 | Water moves through the intercellular spaces |
3 | Water travels through the cytoplasm and plasmodesmata |
1,2, and 3
1 and 2 only
1 and 3 only
3 only
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Which of the following factors does not contribute to the cohesion-tension theory for the transport of water in the xylem?
Evaporation of water from the leaves
Root pressure
Adhesion of water to xylem cell walls
Hydrogen bonds between water molecules
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The translocation rate is related to the hydrostatic pressure created at the source in the phloem sap.
Which of the following correctly describes the correlation of hydrostatic pressure gradient with the rate of translocation?
Higher hydrostatic pressure at the source causes faster translocation
Lower hydrostatic pressure at the source causes faster translocation
Hydrostatic pressure has no effect on the rate of translocation
Translocation occurs independently of hydrostatic pressure
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Which of the following options represents a correct comparison between xylem and phloem?
| Xylem | Phloem |
A | Walls are not lignified | Walls are lignified |
B | Sugars are transported from source to sink | Phloem tissues are dead and hollow |
C | Xylem vessels contain mitochondria | Phloem tissues have companion cells which generate energy |
D | Conduct water and dissolved minerals | Sugars are transported from source to sink |
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The figure below shows a drawing of a light microscope image. The image is a cross-section taken from the stem of a dicotyledonous plant.
Which of the rows, A to D, correctly identifies the name of the tissue labelled E and the functions of tissue F and tissue G?
| Name of tissue E | Function of tissue F | Function of tissue G |
A | cambium | transport of assimilates | transport of water |
B | cambium | transport of water | transport of assimilates |
C | palisade cells | transport of assimilates | transport of water |
D | palisade cells | transport of water | transport of assimilates |
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Which of the following statements, A to D, does not correctly describe the structure or formation of plant vascular tissues?
Companion cells are linked to xylem vessels by plasmodesmata.
Mature sieve tube elements do not contain nuclei.
Phloem and xylem are formed by differentiation of vascular meristems.
Xylem vessels have non-lignified pits to allow movement in and out.
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Which of the following statements, A to D, describes the movement of water across plant roots?
The Casparian strip blocks movement by the symplast pathway.
The symplast pathway requires water to cross partially permeable membranes.
Water moves from the soil to the root hair cells up a water potential gradient.
Water moves through the leaves only by the symplast pathway and across the roots only by the apoplast pathway.
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Which of the statements, A to D, applies to transpiration and evaporation?
It occurs at a faster rate at higher humidity.
It occurs at a slower rate at greater wind speed.
It occurs at a slower rate at higher temperature.
It occurs at the surface of leaves.
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Which of the following statements about water transport in plants is/are correct?
Transpiration happens as a consequence of the need for gas exchange.
There are cohesive forces between water molecules because they form hydrogen bonds with one another.
Water is drawn up the stem due to adhesive forces between water molecules.
1, 2 and 3
Only 1 and 2
Only 2 and 3
Only 1
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Large multicellular animals need a transport system for oxygen and carbon dioxide.
Large multicellular plants do not need a transport system for oxygen and carbon dioxide.
Which of the following statements, A to D, correctly explains these observations?
Large plants have a low surface area to volume ratio.
Plant cells have a low metabolic rate.
Plants generate ATP during photosynthesis, so they do not need to respire.
Plants generate oxygen during photosynthesis.
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Mistletoe is a plant parasite that lives on the stems of other plants. It survives by removing water and assimilates from the host plant.
The mistletoe binds to the stem of the host plant and grows a specialised root-like tissue called a haustorium that attaches to different tissues in the stem.
One species of mistletoe, Viscum minimum, contains no chloroplasts.
Which of the options, A to D, explains why V. minimum does not need chloroplasts?
the haustorium of V. minimum attaches to sieve tube elements
the haustorium of V. minimum attaches to xylem vessels
the haustorium of V. minimum attaches to meristem cells
the haustorium of V. minimum attaches to cambium tissue
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The following mechanisms are used to move water through plants:
i) diffusion
ii) osmosis
iii) mass flow.
Which row correctly identifies the mechanism used at each point of the transpiration stream?
| Into root cells | Across root via symplast pathway | Up the stem in the xylem | Across leaf via apoplast pathway | Out of leaf via stomata |
A | osmosis | osmosis | mass flow | mass flow | diffusion |
B | diffusion | osmosis | osmosis | mass flow | diffusion |
C | diffusion | osmosis | osmosis | mass flow | osmosis |
D | osmosis | osmosis | mass flow | mass flow | osmosis |
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Which of the following best describes the factor that determines the direction of mass flow of phloem sap around a plant?
The active loading of sucrose into phloem sieve tubes near the sink will create a hydrostatic pressure gradient that will facilitate mass flow between the source and sink.
The movement of water molecules in the phloem sieve tubes from the source to the sink will contribute to the hydrostatic pressure gradient between them.
The movement of organic compounds into the phloem sieve tubes near source will increase the hydrostatic pressure in the sieve tubes and create a pressure gradient between source and sink.
The unloading of organic compounds from the phloem sieve tubes at the sink will decrease the water potential of the sieve tubes and create a hydrostatic pressure gradient between the source and sink.
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Which xerophytic adaptations reduce the water potential gradient between the plant and the surrounding air?
epidermal hairs
sunken stomata
reduced number of stomata
rolled leaves
defensive spines
1, 2, 3, 4 and 5
Only 1, 2 and 4
Only 1, 4 and 5
Only 1, 2, 3 and 5
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Which of the following statements about transport in plants is correct.
Water moves from the soil into root hair cells because the root hair cell has a higher water potential than the soil water.
In the apoplast pathway water moves through the cell walls and intercellular spaces without crossing any cell membranes.
Cohesion between water molecules and adhesion between water molecules and the walls of xylem vessels help maintain the transpiration stream.
1, 2 and 3
Only 1 and 2
Only 2 and 3
Only 1
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Scientists investigating translocation in a plant stem made the following observations:
Treating the phloem with a respiratory inhibitor stops the flow of sap
The pH of the companion cells is higher than the surrounding tissues.
Which row correctly identifies how observations 1 and 2 relate to the mass flow hypothesis?
Option | Observation 1 | Observation 2 |
|---|---|---|
A | Contradicts hypothesis | Contradicts hypothesis |
B | Supports hypothesis | Supports hypothesis |
C | Supports hypothesis | Contradicts hypothesis |
D | Contradicts hypothesis | Supports hypothesis |
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The image shows a transverse section of Ammophila arenaria, also known as marram grass.
Which of the following correctly explain the features of marram grass?
The rolled leaf encloses a humid air space, reducing the water vapour concentration gradient between the stomata and the surrounding air.
Sunken stomata increase the distance water vapour must travel, increasing the rate of diffusion out of the leaf.
Spines on the inner leaf surface deter herbivores, reducing water loss through grazing damage.
The thick waxy cuticle on the outer leaf surface reduces the permeability of the epidermis to water vapour.
1, 2 and 4 only
1 and 4 only
1, 2, 3 and 4
3 and 4 only
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Which of the following statements describes the benefit of cohesion in plants?
Water can move as a continuous column from roots to shoots.
Mineral ions can be taken up into root hair cells.
Capillarity aids movement of water through the xylem.
Water transports glucose from source to sink.
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Approximately 1% of flowering plants are parasitic and survive by removing assimilates and water from other plants. All parasitic plants have a specialised organ called a haustorium which penetrates stem tissues and forms a living bridge between the plants.
One genus of parasitic plant, Balanophora, has been found to have lost any genes associated with photosynthesis within its DNA.
Which of the following options explains why the loss of these genes does not negatively impact Balanophora?
The haustorium of Balanophora attaches to xylem vessels.
The haustorium of Balanophora attaches to meristem cells.
The haustorium of Balanophora attaches to cambium tissue.
The haustorium of Balanophora attaches to sieve tube elements.
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The results below are from an investigation into the effect of air movement on the rate of transpiration.
The experiment was replicated five times with a fan switched off and five times with a fan switched on.
Replicate number | Distance travelled by bubble in 5 minutes (mm) | |
Fan switched off | Fan switched on | |
1 | 83 | 119 |
2 | 86 | 123 |
3 | 92 | 120 |
4 | 90 | 124 |
5 | 83 | 121 |
Mean | 86.8 | 121.4 |
Standard deviation | 4.09 |
|
Which of the following is the correct standard deviation for the data with the fan switched on and a correct comparison of the two calculated standard deviations?
| Fan switched off standard deviation | Comparison of standard deviations |
A | 2.07 | The data with the fan switched off is more dispersed around the mean that the data with the fan switched on. |
B | 4.30 | The data with the fan switched off is more dispersed around the mean that the data with the fan switched on. |
C | 2.07 | The data with the fan switched on is more dispersed around the mean that the data with the fan switched off. |
D | 4.30 | The data with the fan switched on is more dispersed around the mean that the data with the fan switched off. |
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The following statements refer to the movement of assimilates from source to sink.
Which of the following statements is/are true?
1 | In the companion cells, sucrose is moved into the cytoplasm in an active process. |
2 | Some of the water that carries the assimilates to the sink is drawn into the transpiration stream in the xylem. |
3 | Sieve elements have many infoldings in their cell membranes to increase surface area. |
1, 2 and 3
Only 1 and 2
Only 1 and 3
Only 1
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During an experiment into the rate of transpiration in a plant, a student calculated the rate of transpiration to be 24 mm3 min-1.
The total leaf surface area of the shoot was estimated to be 56 cm2.
Which of the following is the correct rate of transpiration in cm3 hr-1 cm-2?
2.6 x 10-1 cm3 hr-1 cm-2
7.1 x 10-6 cm3 hr-1 cm-2
2.6 x 10-2 cm3 hr-1 cm-2
7.14 cm3 hr-1 cm-2
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