Transport in Plants

11 Grade 10 General Science questions on Transport in Plants, with worked marking schemes. 11 questions are available on this topic in full.

1. Question 1

   5 marks

   Describe an experiment you would carry out, using cobalt(II) chloride paper, to compare the rate of transpiration from the upper and lower surfaces of a leaf of a bean plant. Include the expected result and its explanation. (5 marks)

   (5 marks)

   Marking scheme

   Procedure: any three of the following, 1 mark each (3 marks): - Using forceps (cobalt(II) chloride is toxic; avoid touching it and wash hands afterwards), pick two squares of dry blue cobalt(II) chloride paper - Place one square on the upper surface and one on the lower surface of a leaf still attached to a well-watered bean plant - Hold each square in place with glass slides clipped together (or clear adhesive tape) to keep out moisture from the air - Start a stopwatch and record the time taken for each square to change from blue to pink Expected result (1 mark): - The paper on the lower surface turns pink faster than the one on the upper surface Explanation (1 mark): - The lower surface has more stomata than the upper surface, so more water vapour is lost from it

2. Question 2

   1 mark

   Plants growing naturally in dry areas such as Turkana lose very little water by transpiration. Which leaf feature helps such plants reduce water loss?

   A. Large air spaces between mesophyll cells

   B. Stomata sunken in pits on the leaf surface

   C. Broad, thin leaves with a large surface area

   D. A thin cuticle that lets light pass easily

   (1 mark)

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3. Question 3

   5 marks

   (a) State the main plant nutrient supplied by urea fertiliser. (1 mark)

   (b) A farmer applied a large amount of Calcium Ammonium Nitrate (CAN) close to the stems of young bean seedlings on dry soil. A few days later the seedlings wilted and their leaves appeared scorched. Explain this observation. (2 marks)

   (c) Explain how excessive use of fertilisers on farms near a river can harm aquatic life. (2 marks)

   (5 marks)

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4. Question 4

   4 marks

   A Grade 10 class plans to sensitise farmers in their community on how to sustain the growth of vegetables.

   (a) Explain two reasons why regular watering sustains plant growth. (2 marks)

   (b) Explain two ways in which adding well-decomposed manure to the soil sustains plant growth. (2 marks)

   (4 marks)

   Marking scheme

   (a) Any two of the following, 1 mark each (2 marks): - Water dissolves mineral salts in the soil so they can be absorbed and carried up the xylem to the leaves - Water keeps cells turgid, supporting the leaves and stems of non-woody plants - Water is a raw material for photosynthesis, so food for growth is made - Transpiration of water cools the leaves on hot days - Water is the medium in which food is translocated and chemical reactions take place in cells (b) Any two of the following, 1 mark each (2 marks): - It releases mineral nutrients (such as nitrogen, phosphorus and potassium) into the soil as it decomposes - It improves the water-holding capacity of the soil, so water is available to roots for longer - It improves soil structure and aeration, allowing roots to respire and absorb water and mineral salts - It encourages useful soil organisms such as earthworms that further improve the soil

5. Question 5

   4 marks

   (a) In translocation, food moves from a 'source' to a 'sink'. Explain what is meant by each of these terms, giving an example of each in an Irish potato plant that is forming tubers. (2 marks)

   (b) When a stored Irish potato tuber is planted, food moves out of the tuber to the young shoots. Explain why the direction of translocation has changed compared with when the tuber was forming. (2 marks)

   (4 marks)

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6. Question 6

   6 marks

   In an investigation, learners covered the soil in a pot of a well-watered maize plant with polythene and weighed the potted plant every two hours to find the rate of water loss. The results are shown below. Time of day: 06:00, 08:00, 10:00, 12:00, 14:00, 16:00, 18:00, 20:00 Rate of water loss (g per hour): 0.4, 1.2, 2.6, 3.8, 4.2, 3.0, 1.0, 0.3

   (a) Plot a graph of the rate of water loss against the time of day. (3 marks)

   (b) Explain why the rate of water loss increased between 08:00 and 14:00. (2 marks)

   (c) Explain why the rate of water loss was lowest at 20:00. (1 mark)

   (6 marks)

   Marking scheme

   (a) (3 marks): - Both axes correctly labelled with units: time of day on the horizontal axis, rate of water loss (g per hour) on the vertical axis (1) - Suitable uniform scales that use most of the grid (1) - All eight points correctly plotted and joined with a smooth curve or straight lines (1) (b) 1 mark each (2 marks): - Light intensity increased, causing the stomata to open wider - Temperature rose, increasing the evaporation of water from the mesophyll cells and the diffusion of water vapour out of the leaves (Accept: humidity of the air fell during the day, increasing the diffusion gradient, as an alternative to either point.) (c) (1 mark): - It was dark, so the stomata were closed (accept: lower temperature reduced evaporation)

7. Question 7

   3 marks

   Mr Otieno transplanted two sukuma wiki (kale) seedlings on a sunny afternoon. Seedling X was lifted with a ball of soil around its roots, while seedling Y was pulled out of the soil with bare roots. Seedling Y wilted badly while X did not. Explain why seedling Y wilted. (3 marks)

   (3 marks)

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8. Question 8

   1 mark

   Farmers in Uasin Gishu apply Di-ammonium Phosphate (DAP) fertiliser in the planting holes when planting maize. What is the main reason for applying DAP at planting?

   A. It supplies potassium needed for leafy growth

   B. It supplies phosphorus for early root growth

   C. It supplies calcium to neutralise acidic soils

   D. It releases nitrogen only after the crop flowers

   (1 mark)

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9. Question 9

   1 mark

   A farmer in Murang'a accidentally removed a complete ring of bark, down to the wood, from the stem of a young avocado tree. After some weeks, the bark just above the ring swelled. Which of the following best explains the swelling?

   A. Mineral salts collected since transpiration had stopped

   B. Water from the roots collected where xylem was cut

   C. Sugars from the leaves collected where phloem was cut

   D. Cells above the ring divided rapidly to heal the cut

   (1 mark)

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10. Question 10

    1 mark

    A soil test on a farm in Nakuru showed that the concentration of nitrate ions in the soil water was lower than in the cell sap of the maize root hair cells. The root hairs still absorbed nitrate ions from the soil. By which process were the ions absorbed?

    A. Active transport using respiratory energy

    B. Imbibition by the cellulose cell walls

    C. Diffusion down a concentration gradient

    D. Mass flow through the phloem sieve tube cells

    (1 mark)

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11. Question 11

    4 marks

    Describe how water moves from the roots to the leaves of a tall eucalyptus tree. (4 marks)

    (4 marks)

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