Transport in plantsIB MYP Biology: Subtopic test

1. 1
   A student in a school in Kenya stands a white carnation in a beaker of water containing red food dye. After one day, red streaks have appeared along the stem and in the petals of the flower.

   (a)

   Which tissue carried the red dye up the stem of the carnation?

   [1 mark]

   • APhloem
   • BXylem
   • CEpidermis
   • DPalisade mesophyll

   (b)

   Besides water, which substance is transported in the xylem?

   [1 mark]

   • ASucrose
   • BStarch
   • CMineral ions
   • DOxygen gas

   (c)

   Explain how the structure of xylem vessels makes them well adapted to carry water up a tall stem.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A forester removes a complete ring of bark, including the phloem, from around the trunk of a young tree. Over the following months the trunk swells just above the ring, and the roots below the ring slowly die, although the leaves stay green for some time.

   (a)

   Which substance builds up in the trunk just above the ring because it cannot travel downwards?

   [1 mark]

   • ASucrose
   • BMineral ions
   • CWater
   • DCarbon dioxide

   (b)

   What is the name for the movement of sucrose from the leaves to other parts of the plant?

   [1 mark]

   • AOsmosis
   • BTranspiration
   • CDiffusion
   • DTranslocation

   (c)

   Explain why the roots below the ring slowly die.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student uses a potometer, which measures how much water a cut leafy shoot takes up, to investigate the effect of wind on transpiration. She uses shoots of the same plant species with similar numbers of leaves. She places an electric fan 50 cm, 100 cm and 150 cm from the shoot and records how far an air bubble moves along the capillary tube in 10 minutes. She repeats each distance three times in a room at 22 °C. The mean bubble movement is 42 mm with the fan at 50 cm, 30 mm at 100 cm and 21 mm at 150 cm.

   (a)

   Identify the independent variable, the dependent variable and one control variable in this investigation.

   [3 marks]

   (b)

   Describe the trend in the results and explain it using ideas about transpiration.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A farming cooperative in a hot, dry region grows tomatoes. The wells that supply its water are running low. The cooperative is considering covering its fields with plastic-covered polytunnels, which keep the air humid, cooler and sheltered from the wind, and watering the plants through drip pipes that deliver small amounts of water straight to the roots.

   (a)

   Explain how water moves from the soil into a tomato plant and up to its leaves, and why the plants would lose less water inside the polytunnels.

   [6 marks]

   (b)

   Discuss and evaluate the cooperative's plan to use polytunnels and drip irrigation to grow its tomatoes.

   [6 marks]

   Total for question 4: 12 marks

End of questions