Transport in Plants: Xylem, Phloem, Transpiration, Translocation and Root Hair Cells

1. A root hair cell contains a higher concentration of nitrate ions than the soil water around it.
   How can nitrate ions continue to enter the root hair cell?

A diffusion through the cell wall
B osmosis through the cell membrane
C active transport using energy from respiration
D transpiration pull through the phloem

2. Which pathway correctly shows movement of water from soil into a leaf?

A root hair cell → cortex → xylem → mesophyll cell
B root hair cell → phloem → cortex → mesophyll cell
C cortex → root hair cell → phloem → xylem
D xylem → cortex → root hair cell → mesophyll cell

3. Which feature of a root hair cell increases water uptake?

A thick waterproof cuticle
B long extension giving large surface area
C absence of cell membrane
D many chloroplasts for photosynthesis

4. A plant is placed in a solution containing cyanide, which stops respiration.
   Which process would be most directly reduced first?

A water entering root hair cells by osmosis
B nitrate ions entering root hair cells by active transport
C water evaporating from mesophyll cells
D oxygen diffusing through stomata

5. Which statement about xylem vessels is correct?

A they are living cells with sieve plates
B they transport sucrose in both directions
C they are dead hollow tubes strengthened with lignin
D they contain companion cells with many mitochondria

6. Which statement about phloem is correct?

A it transports water and mineral ions only upwards
B it transports sucrose and amino acids between sources and sinks
C it is made only of dead hollow vessels
D it transports oxygen from leaves to roots

7. A ring of bark containing phloem is removed from the stem of a plant, but the xylem remains intact.
   What is most likely to happen above the ring?

A sugars accumulate above the ring
B water transport immediately stops
C mineral ions can no longer enter roots
D transpiration stops because stomata close permanently

8. Which process is responsible for most water loss from a plant?

A translocation
B transpiration
C active transport
D photosynthesis only

9. Which row correctly compares xylem and phloem?

A xylem: sucrose; phloem: water
B xylem: water and mineral ions; phloem: sucrose and amino acids
C xylem: amino acids; phloem: oxygen
D xylem: glucose only; phloem: nitrate ions only

10. A plant has its stomata closed for several hours during the day.
    Which effect is most likely?

A increased carbon dioxide entry and increased transpiration
B decreased carbon dioxide entry and decreased transpiration
C increased oxygen entry and increased water uptake
D decreased sucrose transport because xylem stops working

11. Which condition would produce the highest rate of transpiration?

A humid air, low temperature, no wind
B dry air, high temperature, windy conditions
C humid air, high temperature, still air
D dry air, low temperature, no wind

12. Why does high humidity reduce transpiration?

A it lowers the water potential gradient between leaf air spaces and outside air
B it increases the number of open stomata permanently
C it stops water moving in the xylem completely
D it increases active transport of water into guard cells

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

13. Which statement about transpiration pull is correct?

A evaporation from mesophyll cells helps pull water up xylem vessels
B sucrose movement in phloem pulls water down xylem vessels
C water is actively pumped up xylem using ATP
D transpiration pull occurs only at night when stomata close

14. A student uses a potometer to estimate transpiration rate.
    What does the potometer directly measure?

A exact mass of water evaporated from leaves
B rate of water uptake by the shoot
C rate of photosynthesis in palisade cells
D concentration of sucrose in phloem

15. In a potometer experiment, an air bubble moves 24 mm in 6 minutes.
    What is the bubble movement rate?

A 0.25 mm/min
B 4 mm/min
C 18 mm/min
D 144 mm/min

16. A potometer capillary tube has a cross-sectional area of 0.5 mm². An air bubble moves 40 mm in 10 minutes.
    What is the rate of water uptake?

A 2 mm³/min
B 20 mm³/min
C 200 mm³/min
D 800 mm³/min

17. Which precaution is most important when setting up a potometer?

A allowing air bubbles to enter the xylem freely
B cutting the shoot under water
C removing all leaves from the shoot
D placing the apparatus in boiling water

18. Why is a potometer not a perfect measure of transpiration?

A some absorbed water is used in photosynthesis and maintaining turgor
B xylem transports only sucrose
C water cannot move through cut stems
D stomata never open in experimental plants

19. Which feature helps xerophytes reduce water loss?

A large thin leaves with many stomata on upper surface
B sunken stomata and thick waxy cuticle
C no roots and no xylem vessels
D permanently open stomata

20. Which statement about guard cells is correct?

A they become turgid to open stomata
B they become flaccid to open stomata
C they are dead cells with lignified walls
D they transport water upward through the stem

21. A plant is placed in bright light. Stomata open.
    Which effect is most likely?

A transpiration rate decreases because water cannot evaporate
B carbon dioxide entry and water loss both increase
C oxygen cannot leave the leaf
D phloem stops transporting sucrose

22. Which tissue is mainly responsible for transporting mineral ions from roots to leaves?

A phloem
B xylem
C epidermis
D cambium

23. Which statement explains why xylem walls are lignified?

A lignin allows active transport of nitrate ions
B lignin strengthens vessels and prevents collapse under tension
C lignin digests cellulose in root hairs
D lignin converts sucrose into starch

24. Which plant tissue contains sieve tube elements and companion cells?

A xylem
B phloem
C epidermis
D palisade mesophyll

25. Which statement about translocation is correct?

A it is the movement of water only through xylem
B it is the movement of sucrose and amino acids through phloem
C it occurs only from roots to leaves
D it is evaporation of water from mesophyll cells

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

26. A plant stores starch in its roots during summer. During early spring, stored starch is converted to sucrose and transported to growing buds.
    Which statement is correct?

A roots act as sinks in spring
B roots act as sources in spring
C buds act as sources in spring
D xylem transports sucrose from roots to buds

27. Which pair correctly identifies a source and a sink during active growth?

A mature leaf: source; growing root tip: sink
B growing shoot tip: source; mature leaf: sink
C root hair cell: source of sucrose; xylem: sink
D flower petal: source of mineral ions; phloem: sink

28. Which substance is usually transported in phloem rather than xylem?

A nitrate ions
B sucrose
C water
D magnesium ions

29. Which factor would increase water uptake by roots most directly?

A reducing transpiration to zero
B increasing transpiration from leaves
C removing all xylem vessels
D preventing evaporation from mesophyll cells permanently

30. A plant is placed in windy conditions.
    Why does transpiration increase?

A wind removes water vapour from around stomata, maintaining a steep diffusion gradient
B wind causes phloem to carry more water upward
C wind converts water vapour into sucrose
D wind makes root hairs absorb water by diffusion instead of osmosis

31. A student coats the upper surface of a leaf with petroleum jelly. Transpiration decreases slightly. The lower surface is then coated and transpiration decreases greatly.
    What does this suggest?

A more stomata are on the lower surface
B more xylem vessels are on the lower surface
C photosynthesis only occurs on the lower surface
D water enters leaves through the lower surface

32. Which statement correctly describes water movement from soil into root hair cells?

A water moves by osmosis from lower water potential in soil to higher water potential in cell sap
B water moves by osmosis from higher water potential in soil to lower water potential in cell sap
C water moves by active transport using carrier proteins
D water moves through phloem into root hair cells

33. Root hair cells absorb mineral ions by active transport.
    Why do they contain many mitochondria?

A to produce oxygen for diffusion
B to release energy for active transport
C to store sucrose in the vacuole
D to make the cell wall waterproof

34. Which condition would most likely cause wilting?

A water loss by transpiration exceeds water uptake by roots
B water uptake exceeds transpiration for many hours
C phloem transports sucrose too slowly at night only
D photosynthesis produces too much oxygen

35. A plant cell in the leaf loses water faster than it gains water.
    What happens to its turgor pressure?

A increases
B decreases
C remains constant
D becomes oxygen pressure

36. Which statement about wilting is correct?

A wilting occurs when cells lose turgor
B wilting occurs when xylem becomes full of sucrose
C wilting is caused by excessive uptake of nitrate ions only
D wilting means all plant cells are dead

37. Which adaptation would reduce transpiration but may also reduce photosynthesis?

A closing stomata
B increasing leaf surface area
C making the cuticle thinner
D increasing wind speed around the leaf

38. Which statement about water movement in xylem is correct?

A it requires living xylem cells to pump water with ATP
B it is helped by transpiration pull, cohesion and adhesion
C it occurs only downwards from leaves to roots
D it carries mainly glucose and amino acids

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

39. A leafy shoot is placed in a potometer. The bubble moves faster when a fan is switched on.
    Which variable has been changed?

A humidity
B wind speed
C carbon dioxide concentration
D root pressure only

40. In a potometer investigation, why must the joints be airtight?

A to prevent air entering and breaking the continuous water column
B to stop oxygen from leaving by photosynthesis
C to prevent sucrose entering the capillary tube
D to make xylem transport glucose instead of water

41. Which statement about root pressure is correct?

A it can help push water into xylem from roots
B it is the main cause of all transpiration in leaves
C it only occurs in phloem sieve tubes
D it requires stomata to be permanently closed

42. Which part of a leaf is the main site of evaporation during transpiration?

A surface of mesophyll cells into air spaces
B inside xylem vessel walls only
C inside phloem sieve tubes only
D waxy cuticle of upper epidermis only

43. Which statement about water vapour movement out of leaves is correct?

A it diffuses from leaf air spaces through stomata to the outside air
B it is actively transported through xylem into the air
C it moves by osmosis through the cuticle
D it is carried out in phloem with sucrose

44. Which row correctly shows the effect on transpiration?

A higher temperature: decreases transpiration
B higher humidity: increases transpiration
C stronger wind: increases transpiration
D lower light intensity: increases stomatal opening and transpiration

45. A plant is kept in darkness.
    Which effect is most likely?

A stomata may close, reducing transpiration
B stomata open wider to absorb oxygen for photosynthesis
C transpiration becomes faster than in bright light in all cases
D xylem starts transporting sucrose

46. Which statement best explains why mineral ion deficiency may reduce plant growth?

A mineral ions are needed to make molecules such as proteins and chlorophyll
B mineral ions replace water during transpiration
C mineral ions are the main product of photosynthesis
D mineral ions are digested by phloem enzymes

47. A plant is supplied with radioactive carbon dioxide. Later, radioactivity is detected in sucrose moving in the stem.
    Which tissue is most likely carrying the radioactive sucrose?

A xylem
B phloem
C cuticle
D root epidermis only

48. A student removes a complete ring of tissue from a stem, including both xylem and phloem.
    Which result is most likely?

A water and sucrose transport across the ring are both disrupted
B only sucrose transport is affected
C only water transport is affected
D neither water nor sucrose transport is affected

49. Which structure controls the size of stomatal pores?

A guard cells
B xylem vessels
C root hair cells
D sieve plates

50. Which statement is correct?

A transpiration is movement of sucrose from source to sink
B translocation is movement of water from roots to leaves
C transpiration is loss of water vapour from aerial parts of plants
D translocation is evaporation of water from mesophyll cells

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

1. Answer: C
   A is wrong because nitrate ions cannot diffuse into the cell when their concentration is already higher inside.
   B is wrong because osmosis is movement of water, not nitrate ions.
   C is correct because nitrate ions enter against the concentration gradient by active transport using energy from respiration.
   D is wrong because transpiration pull moves water in xylem, not nitrate ions through phloem.

2. Answer: A
   A is correct because water moves from root hair cells through cortex cells into xylem and then to mesophyll cells in leaves.
   B is wrong because phloem transports sucrose and amino acids, not water from roots to leaves.
   C is wrong because water does not start in the cortex before entering root hair cells.
   D is wrong because it reverses the direction of water movement.

3. Answer: B
   A is wrong because a thick waterproof cuticle would reduce absorption.
   B is correct because the long extension increases surface area for water uptake.
   C is wrong because root hair cells have cell membranes.
   D is wrong because root hair cells are underground and usually do not contain chloroplasts.

4. Answer: B
   A is wrong because osmosis itself does not directly require energy from respiration.
   B is correct because active transport of nitrate ions requires energy from respiration, so cyanide reduces it.
   C is wrong because evaporation from mesophyll cells is not directly powered by respiration.
   D is wrong because oxygen diffusion through stomata is passive.

5. Answer: C
   A is wrong because sieve plates are found in phloem, not xylem.
   B is wrong because sucrose is transported in phloem.
   C is correct because xylem vessels are dead hollow tubes strengthened with lignin.
   D is wrong because companion cells are part of phloem.

6. Answer: B
   A is wrong because water and mineral ions are transported mainly in xylem.
   B is correct because phloem transports sucrose and amino acids between sources and sinks.
   C is wrong because phloem contains living sieve tube elements and companion cells.
   D is wrong because phloem does not transport oxygen from leaves to roots.

7. Answer: A
   A is correct because phloem removal prevents downward translocation, so sugars accumulate above the ring.
   B is wrong because xylem remains intact, so water transport can continue.
   C is wrong because mineral ion entry into roots is not directly stopped by removing bark.
   D is wrong because transpiration does not stop permanently.

8. Answer: B
   A is wrong because translocation is movement of sucrose and amino acids in phloem.
   B is correct because transpiration is the main water loss process from aerial parts of plants.
   C is wrong because active transport does not directly cause most water loss.
   D is wrong because photosynthesis uses water but is not the main process of water loss.

9. Answer: B
   A is wrong because it reverses xylem and phloem.
   B is correct because xylem transports water and mineral ions, while phloem transports sucrose and amino acids.
   C is wrong because xylem does not transport amino acids mainly, and phloem does not transport oxygen.
   D is wrong because xylem does not transport glucose only, and phloem does not transport nitrate ions only.

10. Answer: B
    A is wrong because closed stomata reduce carbon dioxide entry and transpiration.
    B is correct because closing stomata decreases carbon dioxide entry and decreases water loss.
    C is wrong because closed stomata do not increase oxygen entry.
    D is wrong because xylem does not stop working simply because stomata close.

11. Answer: B
    A is wrong because humid air, low temperature and no wind reduce transpiration.
    B is correct because dry air, high temperature and wind all increase transpiration.
    C is wrong because humid air reduces the water vapour gradient.
    D is wrong because low temperature and no wind reduce transpiration.

12. Answer: A
    A is correct because high humidity reduces the water potential gradient between the leaf air spaces and outside air.
    B is wrong because humidity does not permanently increase stomatal opening.
    C is wrong because xylem water movement does not completely stop.
    D is wrong because water is not actively transported into guard cells because of humidity.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

13. Answer: A
    A is correct because evaporation from mesophyll cells creates tension that helps pull water up xylem vessels.
    B is wrong because sucrose movement occurs in phloem, not as a pull down xylem.
    C is wrong because xylem vessels are dead and do not actively pump water using ATP.
    D is wrong because transpiration pull is strongest when stomata are open, usually during the day.

14. Answer: B
    A is wrong because a potometer does not directly measure exact water evaporation from leaves.
    B is correct because it directly measures water uptake by the shoot.
    C is wrong because it does not directly measure photosynthesis.
    D is wrong because it does not measure sucrose concentration in phloem.

15. Answer: B
    Rate = distance ÷ time = 24 mm ÷ 6 min = 4 mm/min.
    A is too small.
    B is correct.
    C is wrong because it subtracts instead of dividing.
    D is wrong because it multiplies instead of dividing.

16. Answer: A
    Volume moved = distance × cross-sectional area = 40 mm × 0.5 mm² = 20 mm³.
    Rate = 20 mm³ ÷ 10 min = 2 mm³/min.
    A is correct.
    B, C and D are too large due to calculation errors.

17. Answer: B
    A is wrong because air bubbles entering xylem can break the water column.
    B is correct because cutting the shoot under water prevents air entering the xylem.
    C is wrong because removing all leaves would greatly reduce transpiration.
    D is wrong because boiling water would damage/kill the shoot.

18. Answer: A
    A is correct because not all water taken up is lost by transpiration; some is used in photosynthesis and maintaining turgor.
    B is wrong because xylem transports water and mineral ions, not sucrose.
    C is wrong because water can move through cut stems if set up properly.
    D is wrong because stomata can open in experimental plants.

19. Answer: B
    A is wrong because large thin leaves and many upper stomata increase water loss.
    B is correct because sunken stomata and a thick waxy cuticle reduce transpiration.
    C is wrong because plants need roots and xylem for water uptake and transport.
    D is wrong because permanently open stomata would increase water loss.

20. Answer: A
    A is correct because guard cells become turgid and curve apart, opening the stomata.
    B is wrong because flaccid guard cells close stomata.
    C is wrong because guard cells are living cells.
    D is wrong because xylem vessels transport water upward.

21. Answer: B
    A is wrong because open stomata increase water loss, not decrease it.
    B is correct because open stomata allow more carbon dioxide entry and more water vapour loss.
    C is wrong because oxygen can leave through open stomata.
    D is wrong because phloem transport does not stop just because stomata open.

22. Answer: B
    A is wrong because phloem transports sucrose and amino acids.
    B is correct because xylem transports water and mineral ions from roots to leaves.
    C is wrong because epidermis is mainly protective.
    D is wrong because cambium produces new vascular tissue but is not the main transport tissue.

23. Answer: B
    A is wrong because lignin does not allow active transport.
    B is correct because lignin strengthens xylem vessels and prevents collapse under tension.
    C is wrong because lignin does not digest cellulose.
    D is wrong because lignin does not convert sucrose into starch.

24. Answer: B
    A is wrong because xylem contains vessels and tracheids, not sieve tubes and companion cells.
    B is correct because phloem contains sieve tube elements and companion cells.
    C is wrong because epidermis is protective tissue.
    D is wrong because palisade mesophyll is photosynthetic tissue.

25. Answer: B
    A is wrong because water moves mainly through xylem.
    B is correct because translocation is the movement of sucrose and amino acids through phloem.
    C is wrong because translocation can occur in different directions depending on source and sink.
    D is wrong because evaporation from mesophyll cells is transpiration.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

26. Answer: B
    A is wrong because in spring roots are supplying sucrose, not receiving it.
    B is correct because roots act as sources when stored starch is converted to sucrose and transported to buds.
    C is wrong because growing buds are sinks because they use sugars for growth.
    D is wrong because sucrose is transported in phloem, not xylem.

27. Answer: A
    A is correct because a mature leaf produces sucrose and acts as a source, while a growing root tip uses sucrose and acts as a sink.
    B is wrong because a growing shoot tip is usually a sink, not a source.
    C is wrong because root hair cells are not sources of sucrose.
    D is wrong because petals are not sources of mineral ions.

28. Answer: B
    A is wrong because nitrate ions are transported mainly in xylem.
    B is correct because sucrose is transported in phloem.
    C is wrong because water is transported mainly in xylem.
    D is wrong because magnesium ions are transported mainly in xylem.

29. Answer: B
    A is wrong because reducing transpiration to zero reduces transpiration pull.
    B is correct because increased transpiration from leaves increases the pull on water in xylem, increasing water uptake.
    C is wrong because removing xylem stops water transport.
    D is wrong because preventing evaporation reduces transpiration pull.

30. Answer: A
    A is correct because wind removes water vapour around stomata, maintaining a steep diffusion gradient.
    B is wrong because phloem does not carry most water upward.
    C is wrong because wind does not convert water vapour into sucrose.
    D is wrong because water uptake by root hairs is by osmosis, not diffusion.

31. Answer: A
    A is correct because coating the lower surface greatly reduces transpiration, showing more stomata are there.
    B is wrong because xylem vessels are not mainly responsible for surface water loss.
    C is wrong because photosynthesis does not occur only on the lower surface.
    D is wrong because water enters plants mainly through roots, not leaves.

32. Answer: B
    A is wrong because water moves from higher water potential to lower water potential, not the reverse.
    B is correct because soil water has higher water potential than root hair cell sap, so water enters by osmosis.
    C is wrong because water is not actively transported.
    D is wrong because phloem does not carry water into root hair cells.

33. Answer: B
    A is wrong because mitochondria do not produce oxygen.
    B is correct because mitochondria release energy by respiration for active transport of mineral ions.
    C is wrong because mitochondria do not store sucrose.
    D is wrong because mitochondria do not make the cell wall waterproof.

34. Answer: A
    A is correct because wilting occurs when water loss by transpiration is greater than water uptake by roots.
    B is wrong because if water uptake exceeds transpiration, cells remain turgid.
    C is wrong because slow sucrose transport at night alone does not directly cause wilting.
    D is wrong because oxygen production does not cause wilting.

35. Answer: B
    A is wrong because losing water reduces pressure inside the cell.
    B is correct because turgor pressure decreases when the cell loses water.
    C is wrong because turgor pressure changes with water content.
    D is wrong because turgor pressure does not become oxygen pressure.

36. Answer: A
    A is correct because wilting happens when plant cells lose turgor.
    B is wrong because xylem does not become full of sucrose.
    C is wrong because nitrate uptake alone is not the direct cause of wilting.
    D is wrong because wilted cells are not necessarily dead.

37. Answer: A
    A is correct because closing stomata reduces transpiration but also reduces carbon dioxide entry, which may reduce photosynthesis.
    B is wrong because increasing leaf surface area usually increases water loss.
    C is wrong because a thinner cuticle increases water loss.
    D is wrong because wind increases transpiration.

38. Answer: B
    A is wrong because xylem cells are dead and do not pump water with ATP.
    B is correct because water movement in xylem is helped by transpiration pull, cohesion between water molecules and adhesion to xylem walls.
    C is wrong because xylem water mainly moves upwards from roots to leaves.
    D is wrong because glucose and amino acids are transported in phloem.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

39. Answer: B
    A is wrong because the fan mainly changes air movement, not humidity directly.
    B is correct because switching on a fan increases wind speed.
    C is wrong because a fan does not mainly change carbon dioxide concentration.
    D is wrong because root pressure is not the variable changed.

40. Answer: A
    A is correct because airtight joints prevent air entering and breaking the continuous water column.
    B is wrong because airtight joints are not to stop oxygen leaving photosynthesis.
    C is wrong because sucrose is not entering the capillary tube in a potometer.
    D is wrong because xylem does not transport glucose.

41. Answer: A
    A is correct because root pressure can help push water from roots into xylem.
    B is wrong because transpiration pull is usually more important for water movement through the plant.
    C is wrong because root pressure is linked with xylem, not phloem only.
    D is wrong because it does not require stomata to be permanently closed.

42. Answer: A
    A is correct because water evaporates mainly from the surfaces of mesophyll cells into leaf air spaces.
    B is wrong because evaporation is not mainly inside xylem vessel walls.
    C is wrong because phloem sieve tubes transport sucrose, not evaporating water.
    D is wrong because the waxy cuticle reduces evaporation.

43. Answer: A
    A is correct because water vapour diffuses from moist leaf air spaces through stomata to the outside air.
    B is wrong because water vapour is not actively transported through xylem into air.
    C is wrong because osmosis is movement of water through a partially permeable membrane, not through the cuticle into air.
    D is wrong because phloem transports sucrose and amino acids, not water vapour.

44. Answer: C
    A is wrong because higher temperature usually increases transpiration.
    B is wrong because higher humidity decreases transpiration.
    C is correct because stronger wind increases transpiration by removing water vapour from around stomata.
    D is wrong because lower light intensity usually reduces stomatal opening and transpiration.

45. Answer: A
    A is correct because in darkness stomata may close, reducing transpiration.
    B is wrong because oxygen is not absorbed for photosynthesis.
    C is wrong because transpiration is not always faster in darkness.
    D is wrong because xylem does not start transporting sucrose.

46. Answer: A
    A is correct because mineral ions are needed to make molecules such as proteins, chlorophyll, DNA and ATP.
    B is wrong because mineral ions do not replace water during transpiration.
    C is wrong because mineral ions are not the main products of photosynthesis.
    D is wrong because phloem enzymes do not digest mineral ions.

47. Answer: B
    A is wrong because xylem carries water and mineral ions, not radioactive sucrose from photosynthesis.
    B is correct because sucrose made using radioactive carbon dioxide is transported in phloem.
    C is wrong because cuticle is protective, not transport tissue.
    D is wrong because root epidermis is not the main tissue carrying sucrose in the stem.

48. Answer: A
    A is correct because removing both xylem and phloem disrupts both water and sucrose transport across the ring.
    B is wrong because xylem removal also affects water transport.
    C is wrong because phloem removal also affects sucrose transport.
    D is wrong because both transport systems are damaged.

49. Answer: A
    A is correct because guard cells control stomatal pore size by changing shape.
    B is wrong because xylem vessels transport water.
    C is wrong because root hair cells absorb water and mineral ions.
    D is wrong because sieve plates are part of phloem.

50. Answer: C
    A is wrong because movement of sucrose from source to sink is translocation.
    B is wrong because movement of water from roots to leaves is mainly xylem transport.
    C is correct because transpiration is the loss of water vapour from aerial parts of plants.
    D is wrong because evaporation from mesophyll cells is part of transpiration, not translocation.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.