In plants, which two substances does the xylem carry primarily?
Water and sugars
Sugars and mineral ions
Water and mineral ions
Starch and mineral ions
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Syllabus Edition
First teaching 2014
Last exams 2024
In plants, which two substances does the xylem carry primarily?
Water and sugars
Sugars and mineral ions
Water and mineral ions
Starch and mineral ions
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Which of the following is not a consequence of the transpiration stream in plants?
An increased rate of photosynthesis
Plants remaining upright
The plant retaining heat
Supply of mineral ions to plant tissues
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Which row of the table best summarises the interaction of water molecules during water uptake by a plant?
 | Water molecules pulling each other up | Water molecules sticking to the xylem walls | Capillary action |
A. | cohesion | adhesion | adhesion |
B. | cohesion | cohesion | adhesion |
C. | adhesion | adhesion | cohesion |
D. | cohesion | cohesion | cohesion |
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Which of the following is not a water-saving adaptation found in xerophytic plants?
Sunken stomata
High density of chloroplasts
Rolled leaves
Widespread root network
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Which row of the table gives the best summary of the conditions in which mineral ions are taken up by plant roots?
 | Osmolarity in soil | Osmolarity in root hair cell cytoplasm | Transport mechanism |
A. | Low | High | Water channels across membrane |
B. | High | Low | Transporter proteins |
C. | High | High | Via membrane bilayer |
D. | Low | High | Transporter proteins |
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Identify the set of conditions under which transpiration would occur at the slowest rate.
 |
Humidity |
Temperature |
Air movement |
Light intensity |
A |
Low |
Low |
Low |
Low |
B |
High |
Low |
Low |
Low |
C |
High |
High |
Low |
Low |
D |
High |
Low |
High |
Low |
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When a very narrow glass tube known as a capillary tube is dipped into water, water can flow up the tube despite the opposing force of gravity.
What is this model demonstrating?
Translocation
A hydrostatic pressure gradient
Cohesion between water molecules
Adhesion between water molecules
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The following steps describe the process of transpiration.
What is the correct order of the steps?
III → II → IV → I
III → I → IV → II
I → III → IV → II
I → IV → III → II
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Which of the following relates to xylem vessels?
I only
II and III only
I, II and III
III and IV only
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A student drew a diagrammatic representation of a transverse section of a plant stem based on what they saw using a light microscope.
Identify the correct labels required for the drawing above.
 |
I |
II |
III |
IV |
V |
A |
Vascular bundle |
Pith |
Phloem |
Cambium |
Xylem |
B |
Phloem |
Xylem |
Vascular bundle |
Cambium |
Pith |
C |
Vascular bundle |
Xylem |
Pith |
Cambium |
Phloem |
D |
Vascular bundle |
Cambium |
Pith |
 Xylem |
Phloem |
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Identify which of the adaptations below is not found amongst the group of plants known as xerophytes.
Having long hairs on their surface, so air moisture is absorbed at night
Having reduced leaves in the form of spines, so the surface area for transpiration is reduced
Having reduced numbers of stomata, so there are fewer pores through which water can be lost
Having hinge cells that shrink when flaccid, so the leaves roll up
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When water is taken up by roots, what process is responsible for this and what is the cause behind this process?
 |
Process |
Cause |
A |
Cohesion |
The concentration of solutes in the soil is higher than in the roots |
B |
Cohesion |
The concentration of solutes in the soil is lower than in the roots |
C |
Osmosis |
The concentration of solutes in the soil is higher than in the roots |
D |
Osmosis |
The concentration of solutes in the soil is lower than in the roots |
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What does a potometer measure?
The rate of photosynthesis of a plant
The rate of water uptake of a plant
The rate of respiration of a plant
The rate of transpiration of a plant
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Certain environmental factors can affect the rate of transpiration in plants. The effect of one environmental factor on transpiration rate is shown in the graph below.
Identify the environmental factor that is having this effect on transpiration rate.
Temperature
Humidity
Air movement
Light intensity
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Identify the process by which mineral ions in soil move towards the root cell membrane.
Translocation
Transport through proteins known as protein pumps
Osmosis
Mass flow of water
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Which of these is not a function of plasmodesmata in plant cells?
To allow movement of water via the symplast pathway
To enable cell recognition
To allow communication between cells
To allow movement of nutrients between cells
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Certain plants have developed a mutualistic relationship with soil fungi, in which the plant provides sugars to the fungus for respiration.
In what way does the plant receive a benefit in return?
The fungus helps to stabilise the plant's root network in poor / stony soils.
The fungus acts like a sponge to retain water in dry soils after (infrequent) rainfall.
The fungus fixes atmospheric nitrogen and supplies nitrate ions to the plant.Â
The fungus accesses mineral ions in mineral-deficient soils and supplies them to the plant's roots.
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Which table gives the most accurate summary of the movement of water via the apoplast and symplast pathways?
 | Apoplast pathway | Symplast pathway |
Route travelled | Cell walls | Cytoplasm |
Speed of flow | Slow | Fast |
Method of flow | Mass flow | Osmosis |
Volume of water transported | Low | High |
 | Apoplast pathway | Symplast pathway |
Route travelled | Cell walls | Cytoplasm |
Speed of flow | Fast | Slow |
Method of flow | Mass flow | Osmosis |
Volume of water transported | High | Low |
 | Apoplast pathway | Symplast pathway |
Route travelled | Cytoplasm | Cell walls |
Speed of flow | Fast | Slow |
Method of flow | Mass flow | Osmosis |
Volume of water transported | High | Low |
 | Apoplast pathway | Symplast pathway |
Route travelled | Cell walls | Cytoplasm |
Speed of flow | Fast | Slow |
Method of flow | Osmosis | Mass flow |
Volume of water transported | High | Low |
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The following data were gathered from an experiment into the rate of transpiration in samples of plants in the genus Coelus, commonly grown by gardeners for herbaceous borders. Coelus grows easily in UK gardens and thrives in the relatively high rainfall that the UK experiences.
Marram grass is a xerophyte that is found on sand dunes and other fast-draining soils in coastal areas. The same experimental set-up was repeated with marram grass.Â
Which graph of A - D would be the most likely graph for a comparable experiment carried out on marram grass?
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The diagram shows a potometer set up to measure the rate of transpiration in a piece of cut plant.Â
For a potometer with a cylindrical capillary of the internal diameter of d mm, the bubble was measured to travel h mm in an experimental time of s seconds.Â
Which is the correct formula to calculate the rate of transpiration (as a volume of water uptake per unit time) in this experiment?
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