1. 1
   A commercial tomato grower uses a large greenhouse and adjusts lighting, carbon dioxide levels and heating to try to maximise the rate of photosynthesis in the crop.

   (a)

   Which gas is taken in by a tomato plant's leaves for use in photosynthesis?

   [1 mark]

   • AOxygen
   • BCarbon dioxide
   • CNitrogen
   • DWater vapour

   (b)

   Which factor becomes the limiting factor for photosynthesis when the greenhouse lights are switched off at night?

   [1 mark]

   • ALight intensity
   • BCarbon dioxide concentration
   • CTemperature
   • DChlorophyll content

   (c)

   State the word equation for photosynthesis and name the two products formed.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student on a woodland fieldwork trip finds a plant with variegated leaves, which are green in some areas and white in others, and investigates how this affects photosynthesis.

   (a)

   Which structure in a leaf allows carbon dioxide to enter the leaf tissue?

   [1 mark]

   • ACuticle
   • BXylem
   • CPhloem
   • DStomata

   (b)

   Which pigment absorbs light energy for use in photosynthesis?

   [1 mark]

   • AHaemoglobin
   • BMelanin
   • CChlorophyll
   • DKeratin

   (c)

   When the variegated leaf is tested with iodine solution, the green areas turn blue-black but the white areas remain orange-brown. Explain this observation.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A group of students carries out a class investigation into how light intensity affects the rate of photosynthesis in pondweed kept in a beaker of water.

   (a)

   Describe how a student could investigate the effect of light intensity on the rate of photosynthesis using an aquatic plant such as pondweed, including the variables that should be controlled.

   [3 marks]

   (b)

   The students found that as they moved the lamp closer to the pondweed, the rate of bubble production increased at first but then levelled off. Explain these results in terms of limiting factors.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A garden centre is training new staff and wants them to understand why healthy growth depends on both photosynthesis and an adequate supply of mineral ions from the soil.

   (a)

   Describe the structure of a leaf and explain how it is adapted for efficient photosynthesis.

   [6 marks]

   (b)

   Explain the role of mineral ions, including nitrates and magnesium, in plant health, and describe how a plant uses the glucose produced during photosynthesis.

   [6 marks]

   Total for question 4: 12 marks

End of questions