IGCSE Biology Topic 8: Transport in Plants MCQs – 30 Practice Questions with Answers (Cambridge 0610)
Free practice for Cambridge IGCSE Biology 0610 on transport in plants, covering xylem and phloem, water uptake, transpiration and translocation, with every question followed by a short worked explanation.
Xylem, Phloem and Water Uptake
Q1. Which substances does the xylem transport through a plant?
- (A) Sucrose and amino acids, from leaves to growing parts
- (B) Water and mineral ions, mainly upwards from the roots
- (C) Oxygen and carbon dioxide, between leaves and the air
- (D) Hormones and urea, from roots to flowers
Show Answer
Answer: B – Xylem carries water and dissolved mineral ions taken up by the roots to the rest of the plant, and also helps support the plant.
Q2. Which description best fits the structure of a xylem vessel?
- (A) A living tube whose cells are full of cytoplasm and joined by cross walls
- (B) A narrow tube with thin, flexible walls and many tiny pores
- (C) A single long cell with a large nucleus controlling water flow
- (D) A long, hollow tube of dead cells with thick, lignin-strengthened walls
Show Answer
Answer: D – Xylem vessels have no cell contents and no cross walls, so water flows freely through a continuous tube that lignin keeps from collapsing.
Q3. In a cross-section of a non-woody dicotyledonous stem, where is the xylem found relative to the phloem in a vascular bundle?
- (A) On the inner side of the bundle, with phloem on the outer side
- (B) On the outer side of the bundle, with phloem on the inner side
- (C) Mixed evenly through the centre of the stem, with no separate bundles
- (D) Only in the outer skin of the stem, outside the phloem
Show Answer
Answer: A – In a stem vascular bundle the xylem lies towards the inside and the phloem towards the outside.
Q4. What does the phloem transport, and in which directions can it move?
- (A) Water only, always upwards
- (B) Mineral ions only, always downwards
- (C) Sucrose and amino acids, in either direction
- (D) Starch grains only, always towards the leaves
Show Answer
Answer: C – Phloem carries dissolved sucrose and amino acids, and the direction depends on which parts are supplying and which are receiving them.
Q5. Why do root hair cells have a long, thin extension?
- (A) To reach deep into the soil to anchor the plant against wind
- (B) To increase the surface area for absorption
- (C) To carry out photosynthesis in the dark soil
- (D) To store starch made in the leaves
Show Answer
Answer: B – The extension greatly increases the surface area in contact with soil water, so uptake of water and mineral ions is faster.
Q6. By which process does water enter a root hair cell from the soil?
- (A) Active transport, using energy to pump water in
- (B) Translocation, moving sucrose into the cell
- (C) Diffusion of water vapour through the cell wall
- (D) Osmosis, into the cell
Show Answer
Answer: D – Soil water moves by osmosis into the root hair cell, whose cell sap has a lower water potential than the soil water.
Q7. Which sequence shows the pathway of water through a plant, from root to leaf?
- (A) Root hair cells, root cortex cells, xylem, mesophyll cells
- (B) Root cortex cells, phloem, xylem, mesophyll cells
- (C) Root hair cells, phloem, root cortex cells, mesophyll cells
- (D) Mesophyll cells, xylem, root cortex cells, root hair cells
Show Answer
Answer: A – Water enters root hair cells, crosses the root cortex, travels up the xylem, and reaches the mesophyll cells of the leaf.
Q8. A dye is added to the water around the roots of a leafy shoot. After some time, coloured lines appear in the stem and leaf veins. What does this demonstrate?
- (A) That phloem carries water upwards from the roots
- (B) That water is made in the leaves and flows downwards
- (C) That water travels up through the xylem
- (D) That mineral ions are stored in the leaf veins
Show Answer
Answer: C – A stain taken up with water marks the route it follows, showing the xylem pathway through stem and leaves.
Q9. Which feature of xylem vessels is most important for moving large volumes of water quickly?
- (A) Their living cytoplasm, which pumps water upwards
- (B) Their chloroplasts, which release energy for transport
- (C) Their cross walls, which filter out mineral ions
- (D) Their hollow, continuous tubes
Show Answer
Answer: D – With no contents and no cross walls, a xylem vessel is an open tube through which water can flow freely.
Q10. In a root cross-section, which tissue would you expect to find towards the centre, carrying water to the stem?
- (A) Xylem, forming the central transport tissue of the root
- (B) Phloem, forming the central transport tissue of the root
- (C) Epidermis, forming the central transport tissue of the root
- (D) Mesophyll, forming the central transport tissue of the root
Show Answer
Answer: A – The xylem in a root lies centrally and carries absorbed water and mineral ions up into the stem.
Transpiration and the Transpiration Stream
Q11. What is transpiration?
- (A) The uptake of mineral ions by root hair cells
- (B) The loss of water vapour from leaves
- (C) The movement of sucrose in the phloem
- (D) The opening and closing of flowers in sunlight
Show Answer
Answer: B – Transpiration is the loss of water vapour from a plant, chiefly as vapour diffusing out of leaves through open stomata.
Q12. Which sequence correctly describes how water vapour leaves a leaf?
- (A) Water is pumped out of the phloem through the stomata
- (B) Water evaporates directly from the xylem through the leaf surface
- (C) Water evaporates into air spaces, then leaves through the stomata
- (D) Water diffuses from the soil straight through the leaf cuticle
Show Answer
Answer: C – Water first evaporates from the wet surfaces of mesophyll cells into the air spaces, then diffuses out through the stomata as vapour.
Q13. What is meant by the transpiration pull?
- (A) The pull drawing a column of water up the xylem
- (B) The active pumping of water by root hair cells into the xylem
- (C) The suction created when stomata close at night
- (D) The pressure of phloem sap pushing water upwards
Show Answer
Answer: A – As water is lost from leaves, the remaining column of water molecules, held together by attraction between them, is pulled upwards.
Q14. A plant is moved from a still, humid room to a warm, windy place. What will happen to its rate of transpiration, and why?
- (A) It will fall, because wind cools the leaves and closes the stomata
- (B) It will stay the same, because transpiration depends only on light
- (C) It will fall, because warm air holds less water vapour
- (D) It will rise, because temperature and wind both increase loss
Show Answer
Answer: D – Warm air increases evaporation from mesophyll cells, and wind sweeps away water vapour outside the leaf, steepening the diffusion gradient.
Q15. Why does high humidity reduce the rate of transpiration?
- (A) Stomata close completely in humid air and never reopen
- (B) Moist outside air gives a smaller diffusion gradient
- (C) Humid air stops water evaporating from mesophyll cells entirely
- (D) Humid air makes the xylem vessels collapse
Show Answer
Answer: B – Diffusion is faster when the difference in concentration is larger, so moist outside air slows the net loss of vapour from the leaf.
Factors, Wilting and Translocation
Q16. Which change would increase the rate of transpiration from a leafy shoot?
- (A) Moving it into cooler air
- (B) Spraying its leaves with water
- (C) Increasing the wind speed around it
- (D) Placing a plastic bag over the shoot
Show Answer
Answer: C – Faster wind removes water vapour from around the leaf, maintaining a steep gradient for diffusion out of the stomata.
Q17. Leaves have a large internal surface area because of the interconnecting air spaces between mesophyll cells. How does this affect water loss?
- (A) It increases evaporation from mesophyll cell surfaces
- (B) It reduces evaporation because air spaces trap water permanently
- (C) It stops water reaching the stomata altogether
- (D) It forces water to travel through the phloem instead of the xylem
Show Answer
Answer: A – The air spaces expose a large wet surface of mesophyll cells, so much water evaporates into the spaces inside the leaf.
Q18. A potted plant has not been watered for days and its leaves droop. Which explanation of wilting is correct?
- (A) The stomata have grown larger and cannot close
- (B) The phloem has stopped carrying sucrose to the leaves
- (C) The roots have stopped absorbing mineral ions
- (D) Cells lose turgor as water is lost
Show Answer
Answer: D – Wilting happens when cells lose water and turgor pressure falls, so leaves and soft stems droop instead of holding their shape.
Q19. What is translocation?
- (A) The loss of water vapour from leaves through stomata
- (B) The movement of sucrose and amino acids in phloem
- (C) The uptake of water by root hair cells by osmosis
- (D) The transport of mineral ions upwards in the xylem
Show Answer
Answer: B – Translocation is the transport of dissolved food substances, mainly sucrose and amino acids, in the phloem.
Q20. In a plant, which part is acting as a source?
- (A) A growing shoot tip that is using sugars to build new cells
- (B) A developing fruit that is storing sugars
- (C) A leaf releasing sucrose into the phloem
- (D) A root that is storing starch over winter
Show Answer
Answer: C – A source is a part that releases sucrose or amino acids into the phloem, such as a leaf making sugars by photosynthesis.
Q21. Which part is acting as a sink?
- (A) A mature leaf exporting sucrose on a sunny day
- (B) A storage organ releasing sucrose in spring
- (C) A green stem carrying out photosynthesis
- (D) A growing root tip using sugars
Show Answer
Answer: D – A sink uses or stores the sucrose or amino acids delivered by the phloem, such as a growing root tip.
Q22. A storage root releases its stored sugars in spring but stores sugars again in autumn. What does this show?
- (A) The same part of a plant can act as a source at one time and a sink at another
- (B) Roots are always sources and never sinks
- (C) Phloem only transports substances in one direction
- (D) Translocation stops completely in autumn
Show Answer
Answer: A – Whether a part is a source or a sink depends on whether it is releasing or receiving sucrose at that time, and this can change with the season.
Q23. A plant with many leaves but very few roots is placed in dry soil. Which problem is most likely to develop first?
- (A) The leaves will stop photosynthesizing because they lack chlorophyll
- (B) The phloem will fill with water and burst
- (C) The plant will wilt, because water lost by transpiration cannot be replaced fast enough by uptake
- (D) The stomata will remain open permanently
Show Answer
Answer: C – When uptake cannot keep pace with transpiration loss, cells lose turgor and the plant wilts.
Q24. Which pair of changes would both reduce water loss from a leafy shoot on a hot day?
- (A) Increasing wind speed and raising the temperature
- (B) Sheltering the shoot from wind and raising the humidity around it
- (C) Raising the temperature and lowering the humidity
- (D) Increasing wind speed and lowering the humidity
Show Answer
Answer: B – Still, humid air reduces both evaporation and the diffusion gradient, so transpiration falls.
Q25. Why does the number and size of stomata affect the rate of transpiration?
- (A) Stomata store sucrose made in photosynthesis
- (B) Stomata absorb water directly from the air
- (C) Stomata pump water up the xylem by active transport
- (D) Stomata are the main openings through which water vapour diffuses out, so more or larger stomata allow faster loss
Show Answer
Answer: D – Stomata are the main openings for vapour loss, so a leaf with more or larger stomata loses water vapour faster when they are open.
Q26. Which statement about xylem and phloem is correct?
- (A) Xylem transports water and mineral ions, while phloem transports sucrose and amino acids
- (B) Both xylem and phloem transport water upwards only
- (C) Both tissues are made only of living cells
- (D) Neither tissue plays any part in supporting the plant
Show Answer
Answer: A – Xylem carries water and mineral ions upwards, while phloem carries sucrose and amino acids between sources and sinks; xylem vessels are dead cells, not living ones.
Q27. A shoot is kept in still air at a constant temperature. If a fan is switched on, what happens to the water uptake by the shoot, and why?
- (A) It falls, because the fan cools the roots
- (B) It rises, because faster transpiration increases the pull on water through the xylem
- (C) It stays the same, because wind affects only the leaves, not uptake
- (D) It falls, because the fan closes the stomata
Show Answer
Answer: B – Faster water loss from the leaves strengthens the transpiration pull, so more water is drawn up from the roots.
Q28. Which feature helps a leaf reduce water loss while still allowing gas exchange?
- (A) Xylem vessels filled with sucrose
- (B) A large number of root hairs on the leaf
- (C) A thick waxy cuticle that limits evaporation from the leaf surface
- (D) Phloem tubes that are open at both ends
Show Answer
Answer: C – A waxy cuticle reduces evaporation from the leaf surface, while stomata still allow gases to pass when open.
Q29. In spring, sugars stored in a bulb move to the new leaves. Which process and tissue are involved?
- (A) Transpiration in the xylem
- (B) Osmosis in the root hairs
- (C) Photosynthesis in the mesophyll
- (D) Translocation in the phloem, from a source to a sink
Show Answer
Answer: D – Stored sugars are released by the bulb (source) and carried in the phloem to the growing leaves (sink).
Q30. Which statement best explains why a cut stem placed in water stays upright longer than one left in air?
- (A) Water taken up through the xylem replaces water lost by transpiration, keeping cells turgid
- (B) Water in the container feeds the phloem with sucrose
- (C) The stem absorbs oxygen from the water for photosynthesis
- (D) Water blocks the stomata so no transpiration occurs
Show Answer
Answer: A – Replacing lost water maintains turgor pressure in the cells, so the stem and leaves stay firm and upright.
Revisit any questions you missed, especially the difference between transpiration and translocation, then test yourself again until each process feels secure.