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Exam questions · Biology · Plant Tissues and Transport

Translocation and the Phloem

  • 7 exam questions
  • 17 marks
  • 8 quick checks
  1. 1 State [1 mark]

    Name the process by which dissolved sugars are moved round a plant.

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    Model answer

    Translocation.

    Mark scheme

    • Translocation — 1 mark
  2. 2 Name [2 marks]

    Name the tissue in a plant that transports water, and the tissue that transports sugars.

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    Model answer

    Xylem transports water. Phloem transports sugars.

    Mark scheme

    • Xylem for water — 1 mark
    • Phloem for sugars — 1 mark
  3. 3 Describe [3 marks]

    Describe what happens to the sugars made in the leaves of a plant.

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    Model answer

    The sugars are carried in the phloem to other parts of the plant. Some are used immediately for respiration and growth. Some are carried to storage organs and stored.

    Mark scheme

    • Carried in the phloem — 1 mark
    • Used for respiration or growth — 1 mark
    • Stored — 1 mark
  4. 4 Explain [2 marks]

    Explain why the roots of a plant need sugars to be transported to them.

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    Model answer

    The roots are underground and cannot photosynthesise. They need sugars for respiration to release energy for growth and active transport.

    Mark scheme

    • Cannot photosynthesise — 1 mark
    • Need sugars for respiration / energy / growth — 1 mark
  5. 5 Describe [2 marks]

    Describe how the structure of phloem allows sugars to move from one cell to the next.

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    Model answer

    Phloem is made of tubes of elongated cells joined end to end. There are pores in the end walls, so the cell sap can pass from one cell to the next.

    Mark scheme

    • Elongated cells joined end to end — 1 mark
    • Pores in the end walls — 1 mark
  6. 6 Compare [4 marks]

    Compare the structure and function of xylem and phloem.

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    Model answer

    Xylem is made of dead cells that form hollow tubes strengthened with lignin, while phloem is made of living cells with pores in the end walls. Xylem carries water and mineral ions from the roots to the leaves, while phloem carries dissolved sugars from the leaves to the rest of the plant. Xylem carries substances in one direction (up), while phloem can carry them up and down.

    Mark scheme

    • Xylem dead, phloem living — 1 mark
    • Xylem hollow with lignin, phloem pores in end walls — 1 mark
    • Xylem carries water and ions, phloem carries sugars — 1 mark
    • Xylem upwards only, phloem both directions — 1 mark
  7. 7 Explain [3 marks]

    A ring of bark and phloem is removed from around a tree trunk. The xylem is not damaged. Explain why the tree eventually dies.

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    Model answer

    The sugars made in the leaves cannot be carried down the trunk in the phloem. The roots do not receive sugars, so they cannot respire and release energy. The roots die, so the tree can no longer take up water and minerals.

    Mark scheme

    • Phloem cut so sugars cannot reach the roots — 1 mark
    • Roots cannot respire / starved of food — 1 mark
    • Roots die so the tree cannot take up water — 1 mark

Quick check

  1. 1

    What is carried in the phloem?

    1. AWater and minerals
    2. BDissolved sugars
    3. CCarbon dioxide
    4. DOxygen only
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    B: Dissolved sugars

    Phloem carries dissolved sugars from the leaves to the rest of the plant.

  2. 2

    What is the movement of food through the phloem called?

    1. ATranspiration
    2. BOsmosis
    3. CTranslocation
    4. DDiffusion
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    C: Translocation

    Translocation is the movement of dissolved sugars in the phloem.

  3. 3

    Which statement about phloem is correct?

    1. AIt is made of living cells
    2. BIt is made of dead cells
    3. CIt is strengthened with lignin
    4. DIt carries only water
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    A: It is made of living cells

    Phloem is made of living cells with pores in the end walls.

  4. 4

    In which direction can phloem carry sugars?

    1. AOnly up
    2. BOnly down
    3. COnly sideways
    4. DUp and down
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    D: Up and down

    Sugars move from where they are made to where they are needed, which can be up or down the plant.

  5. 5

    Which tissue is strengthened with lignin?

    1. APhloem
    2. BXylem
    3. CEpidermis
    4. DPalisade mesophyll
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    B: Xylem

    Xylem walls contain lignin, which stops the tubes collapsing.

  6. 6

    Where might sugars be stored in a plant?

    1. AIn the guard cells
    2. BIn the xylem
    3. CIn a root
    4. DIn the stomata
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    C: In a root

    Roots, tubers and fruits can all store sugars, often as starch.

  7. 7

    Why can't roots make their own sugars?

    1. AThey get no light
    2. BThey have too many chloroplasts
    3. CThey have no cell walls
    4. DThey are made of xylem only
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    A: They get no light

    Roots are underground, so they get no light for photosynthesis.

  8. 8

    How does cell sap move from one phloem cell to the next?

    1. AThrough lignin
    2. BThrough the stomata
    3. CThrough the guard cells
    4. DThrough pores in the end walls
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    D: Through pores in the end walls

    There are pores in the end walls of the phloem cells.