1. 1
   A gardener places a potted seedling on its side inside a dark cupboard for several days. When examined, the shoot has curved upwards, growing away from the direction of gravity, while the root has curved downwards, growing towards the direction of gravity.

   (a)

   A gardener places a potted seedling on its side in a dark cupboard for several days. When examined, the shoot has curved so that it is growing upwards again, away from the direction of gravity. What is this growth response called?

   [1 mark]

   • APhototropism
   • BGravitropism
   • COsmosis
   • DTranspiration

   (b)

   In the same seedling, the root curves downwards, growing towards the direction of gravity. Which term best describes this response of the root?

   [1 mark]

   • ANegative phototropism
   • BNegative gravitropism
   • CPositive gravitropism
   • DPositive phototropism

   (c)

   Describe gravitropism and state one advantage to a plant of the shoot growing away from gravity.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student places a seedling in a box with a single small hole letting light in from one side. After several days the shoot has bent towards the hole. The student investigates the chemical explanation for this bending by measuring the distribution of a plant hormone in the shoot tip.

   (a)

   What is this growth response called?

   [1 mark]

   • APhototropism
   • BGravitropism
   • CPhotosynthesis
   • DDiffusion

   (b)

   The student finds that the growth hormone is unequally distributed across the shoot tip when light comes from one side. Which hormone controls this bending response in the shoot?

   [1 mark]

   • AInsulin
   • BOestrogen
   • CAdrenaline
   • DAuxin

   (c)

   State where auxin is made in the shoot, and describe what auxin does to plant cells that leads to growth.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A researcher grows two identical seedlings, X and Y, in identical pots of soil. Seedling X is lit evenly from all directions, while seedling Y is lit only from a single direction, and the researcher also removes the tip from a third seedling, Z, to observe the effect on growth.

   (a)

   A researcher grows two identical seedlings. Seedling X is lit evenly from all sides, and seedling Y is lit only from one side. After several days, seedling X grows straight upwards while seedling Y bends towards the light. Explain why seedling X grows straight while seedling Y bends towards the light, in terms of the distribution of auxin.

   [3 marks]

   (b)

   The researcher removes the very tip of seedling Z and finds that the shoot below the cut stops elongating and no longer bends towards light, even when light is shone from one side. Explain these observations in terms of where auxin is produced and how it acts.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A farmer notices that seeds planted at random orientations in the soil all eventually produce shoots that grow upwards and roots that grow downwards. Separately, the farmer observes that seedlings grown in a greenhouse consistently bend towards a single sunlit window rather than growing straight upwards.

   (a)

   Explain, in terms of auxin distribution and its effects on shoots and roots, how this consistent growth pattern is achieved.

   [6 marks]

   (b)

   Seedlings grown in the farmer's greenhouse consistently bend towards a single sunlit window rather than growing straight upwards. Explain why this directional growth towards light is useful to the plant, and describe the chemical mechanism, involving auxin, that produces this bending.

   [6 marks]

   Total for question 4: 12 marks

End of questions