Transport in Plants

20 Grade 10 Biology questions on Transport in Plants, with worked marking schemes. 20 questions are available on this topic in full.

1. Question 1

   4 marks

   A maize crop growing in Machakos is seen to droop at midday but looks fresh again by the following morning. Account for this observation.

   (4 marks)

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2. Question 2

   2 marks

   Distinguish between transpiration and guttation as they occur in a maize plant.

   (2 marks)

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3. Question 3

   1 mark

   A sweet potato plant is forming tubers. During this period the sucrose manufactured in the leaves is translocated

   A. from the leaves to the tubers and back through the same sieve tube at the same time

   B. from the leaves to the tubers through the phloem

   C. from the tubers to the leaves through the xylem

   D. from the leaves to the tubers through the xylem

   (1 mark)

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4. Question 4

   1 mark

   Wind blows steadily across a maize field at Mwea. The rate of transpiration from the maize leaves rises because the moving air

   A. increases the humidity of the layer of air touching the leaf surface

   B. cools the leaves so that the water inside them evaporates more easily

   C. forces water out through the stomata by pressing on the leaf surface

   D. removes the saturated air next to the leaf, keeping the diffusion gradient steep

   (1 mark)

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5. Question 5

   3 marks

   Explain how a root hair cell of a kale plant is adapted to absorbing water and mineral salts from the soil.

   (3 marks)

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6. Question 6

   1 mark

   A mature sieve tube element has no nucleus, yet translocation of food through it requires energy. This energy is supplied by the

   A. xylem vessels lying next to the sieve tube

   B. companion cells lying next to the sieve tube

   C. lignin deposited in the sieve plates

   D. chloroplasts inside the sieve tube element

   (1 mark)

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7. Question 7

   4 marks

   Describe how water moves from the xylem in the roots to the leaves of a tall Grevillea tree.

   (4 marks)

   Marking scheme

   Any 4 of the following, 1 mark each: (i) Water evaporates from the mesophyll cell surfaces into the leaf air spaces and diffuses out through the stomata. (ii) The mesophyll cells, now having a more concentrated sap, draw water from the xylem in the leaf veins, creating a suction force called transpiration pull. (iii) Cohesion between water molecules holds the water in the xylem as a continuous unbroken column that is pulled upwards. (iv) Adhesion between the water molecules and the lignified walls of the xylem vessels keeps the column in place and assists the rise. (v) The xylem vessels are narrow, so water also rises through them by capillarity. (vi) Root pressure developed in the roots pushes water a short way up the stem, especially at night.

8. Question 8

   1 mark

   Water enters the root hair of a kale (sukuma wiki) plant from the surrounding soil because the

   A. soil solution is more concentrated than the cell sap of the root hair

   B. soil solution is more dilute than the cell sap of the root hair

   C. cell wall of the root hair allows only water and not mineral salts to pass

   D. root hair pumps water inwards using energy released during respiration

   (1 mark)

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9. Question 9

   6 marks

   Suggest three practices a farmer can carry out when transplanting tomato seedlings during a dry spell in order to reduce water loss from the seedlings, giving a reason for each practice.

   (6 marks)

   Marking scheme

   Any 3 practices, each with a valid reason; 1 mark for the practice and 1 mark for the reason (maximum 6 marks). Acceptable pairs: (i) Transplant in the evening or on a cloudy day - temperature and light intensity are low, so the rate of transpiration is low while the roots re-establish. (ii) Lift the seedling with a ball of soil around the roots - the delicate root hairs are not damaged, so absorption of water continues immediately after transplanting. (iii) Mulch around the seedlings with dry grass - reduces evaporation of water from the soil and keeps the soil moist for absorption. (iv) Shade the seedlings with dry grass or banana leaves - cuts down light intensity and air movement, lowering the rate of transpiration. (v) Remove or trim some of the older leaves - reduces the surface area from which water vapour is lost. (vi) Water the seedlings immediately after transplanting - keeps the soil solution dilute so water continues to enter the root hairs by osmosis. A reason given without a practice scores 0.

10. Question 10

    4 marks

    Explain why the rate of transpiration in a bean plant growing in Lodwar is higher than that of an identical bean plant growing in Kisii.

    (4 marks)

    Marking scheme

    Any 4 of the following, 1 mark each (each environmental factor must be linked to its effect): (i) Temperature in Lodwar is higher, giving water molecules more energy so evaporation from the mesophyll surfaces and diffusion out of the leaf are faster. (ii) Humidity of the air in Lodwar is lower, so the concentration gradient of water vapour between the leaf air spaces and the outside air is steeper. (iii) Air movement/wind in Lodwar is greater, sweeping away saturated air from the leaf surface and maintaining the steep gradient. (iv) Light intensity in Lodwar is higher, so the stomata open wider and for longer, increasing the area through which water vapour escapes. (v) The soil and air in Lodwar are drier, so the leaves stay at a higher temperature than the shaded, cloud-cooled leaves in Kisii. Marking note: the converse statement about Kisii (cooler, more humid, calmer, cloudier) earns the mark for the corresponding factor.

11. Question 11

    5 marks

    Explain five ways in which a sisal plant growing in the dry parts of Kitui is adapted to reduce loss of water.

    (5 marks)

    Marking scheme

    Any 5 of the following, 1 mark each (adaptation must be linked to reduced water loss): (i) A thick waxy cuticle on the leaf surface, which is impermeable to water and cuts down cuticular transpiration. (ii) Stomata sunken in pits, which trap moist air so the diffusion gradient for water vapour out of the leaf is reduced. (iii) A small number of stomata, reducing the number of openings through which water vapour escapes. (iv) Reduced leaf surface area (narrow, stiff, spiny-edged leaves), which reduces the area exposed for evaporation. (v) Stomata that close during the hot part of the day and open at night, when temperatures are low and the air is cooler. (vi) Thick fleshy leaves that store water, so the plant survives long periods without absorbing more. Do not credit deep or extensive root systems here, since these increase absorption rather than reduce loss.

12. Question 12

    1 mark

    Which feature of a mature xylem vessel allows water to flow through it with the least resistance?

    A. The narrow pores found in the sieve plates of the vessel

    B. The absence of cross walls between the cells forming the vessel

    C. The presence of many mitochondria in the cytoplasm of the vessel

    D. The deposition of lignin in the walls of the vessel

    (1 mark)

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13. Question 13

    1 mark

    A leafy shoot was cut and left standing in water containing a red dye for three hours. The stem was then cut across. The red stain would be found mainly in the

    A. xylem, because it is the tissue through which water and dissolved substances move up the stem

    B. phloem, because it is the tissue that carries dissolved substances in the stem

    C. cortex, because its cells store the water taken up by the shoot

    D. epidermis, because the dye soaks into the stem through its outer surface

    (1 mark)

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14. Question 14

    3 marks

    A farmer applies a heavy dose of fertiliser very close to the base of his cabbages. Within a few days the plants wilt, although the soil is still moist. Explain this observation.

    (3 marks)

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15. Question 15

    1 mark

    In a bean leaf, most of the water lost to the atmosphere on a hot sunny afternoon escapes through the

    A. stomata on the lower epidermis

    B. cuticle covering the upper epidermis

    C. open ends of the xylem vessels in the veins

    D. lenticels found on the leaf stalk

    (1 mark)

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16. Question 16

    1 mark

    A complete ring of bark was removed from the trunk of a healthy mango tree in an orchard in Makueni. After several weeks a swelling developed on the trunk just above the ring. The most likely reason for the swelling is that

    A. water moving up the trunk collected above the ring because the xylem had been removed with the bark

    B. sugars moving down the trunk accumulated above the ring because the phloem had been removed with the bark

    C. the tree formed extra bark above the ring in order to seal off the wound

    D. mineral salts absorbed by the roots could no longer reach the leaves and piled up above the ring

    (1 mark)

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17. Question 17

    4 marks

    Describe four structural features of a sieve tube element and state how each feature suits it for the translocation of manufactured food.

    (4 marks)

    Marking scheme

    Any 4 feature-and-function pairs, 1 mark each: (i) The end walls are perforated sieve plates, whose pores allow the sugary sap to pass from one element to the next along the tube. (ii) The elements are arranged end to end, forming a long continuous tube running from the leaves to all other parts of the plant. (iii) The mature element has no nucleus and only a thin lining of cytoplasm, leaving the lumen free so that sap flows with little resistance. (iv) The walls are thin and made of cellulose (not lignified), allowing sugars to be loaded into and unloaded out of the tube sideways. (v) The element remains living, since translocation is an active process requiring energy. Award 0 for a feature stated without a matching function.

18. Question 18

    1 mark

    The stomata of a bean plant open early in the morning because the guard cells

    A. convert their sugar into starch and become flaccid

    B. absorb water by osmosis from the neighbouring cells and become turgid

    C. lose water to the neighbouring epidermal cells and shrink

    D. are pushed apart by air rushing into the air spaces of the leaf

    (1 mark)

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19. Question 19

    3 marks

    State three ways in which transpiration is important to a growing sukuma wiki plant.

    (3 marks)

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20. Question 20

    1 mark

    Water rises through the xylem of a tall eucalyptus tree as an unbroken column. The property of water molecules that prevents this column from breaking is

    A. the ability of water to dissolve large amounts of mineral salts

    B. the low density of water compared with that of air

    C. adhesion of water molecules to the lignified walls of the vessels

    D. cohesion between one water molecule and the next

    (1 mark)

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