1. 1
   A gardener places a healthy green plant in a sealed transparent container with a supply of carbon dioxide and bright light. After several hours, tests show that glucose has been produced inside the plant's leaves and oxygen has accumulated in the container.

   (a)

   Which process in the plant is responsible for producing the glucose and oxygen?

   [1 mark]

   • ARespiration
   • BPhotosynthesis
   • CTranspiration
   • DActive transport

   (b)

   Which raw materials, other than light energy, are needed by the plant for this process to occur, as shown by the word equation for photosynthesis?

   [1 mark]

   • AOxygen and glucose
   • BStarch and cellulose
   • CNitrate ions and magnesium ions
   • DCarbon dioxide and water

   (c)

   Describe the role of chlorophyll in the process occurring inside the plant's leaves.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A researcher places an aquatic plant in water containing hydrogencarbonate indicator and measures gas exchange in both light and dark conditions. In bright light, the indicator changes colour to show a fall in dissolved carbon dioxide, whereas in the dark, the indicator shows a rise in dissolved carbon dioxide.

   (a)

   What does the rise in carbon dioxide in the dark indicate is occurring in the plant?

   [1 mark]

   • AOnly respiration occurring, with no photosynthesis
   • BPhotosynthesis exceeding respiration
   • CActive transport of carbon dioxide out of the plant
   • DTranspiration releasing carbon dioxide

   (b)

   Why does the carbon dioxide concentration fall in bright light, even though the plant is still respiring at the same time?

   [1 mark]

   • ABecause respiration stops completely in the light
   • BBecause light destroys carbon dioxide molecules
   • CBecause the rate of photosynthesis exceeds the rate of respiration, so more carbon dioxide is used than is produced
   • DBecause the plant releases oxygen instead of carbon dioxide in the light

   (c)

   Describe how the researcher could use this hydrogencarbonate indicator experiment, with appropriate controls, to investigate the need for light in photosynthesis.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A farmer grows tomato plants in a greenhouse and increases the carbon dioxide concentration of the air using a generator, finding that plant growth improves as a result, up to a certain point.

   (a)

   State three factors that can limit the rate of photosynthesis.

   [3 marks]

   (b)

   Explain why increasing carbon dioxide concentration only improves photosynthesis and growth up to a certain point, after which further increases have little effect.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A plant physiologist grows identical seedlings in soil lacking nitrate ions and separately in soil lacking magnesium ions, comparing their growth and leaf colour with seedlings grown in complete soil. She finds that plants lacking magnesium develop pale, yellowing leaves, while plants lacking nitrate show stunted overall growth.

   (a)

   Explain the roles of nitrate ions and magnesium ions in plant growth, linking each deficiency to the symptoms observed.

   [6 marks]

   (b)

   The physiologist also compares how the glucose made by healthy plants (grown in complete soil) is used and stored in different parts of the plant. Explain, with named examples, the different subsequent uses of the carbohydrates made during photosynthesis.

   [6 marks]

   Total for question 4: 12 marks

End of questions