ExpertMedium2 marksMultiple Choice
AQA GCSE · Question 04.2 · Homeostasis and Response
What are two reasons for surrounding the seedlings with damp blotting paper? Choose two options.
What are two reasons for surrounding the seedlings with damp blotting paper? Choose two options.
Answer options:
A.
To prevent photosynthesis in the roots
B.
To prevent the growth of mould on the roots
C.
To prevent water affecting the direction of root growth
D.
To provide enough water for root growth
E.
To provide the roots with mineral ions
How to approach this question
Consider the requirements for a plant to grow and the variables that need to be controlled in this experiment. Roots need water to live, so one reason is to supply it. Roots also respond to water (hydrotropism). How does the damp blotting paper ensure gravity is the main stimulus being tested?
Full Answer
The damp blotting paper serves two important functions in this experiment:
1. **Provides Water for Growth:** Water is essential for the seedling to survive and grow. It is required for metabolic processes and for cell turgor, which is necessary for cell elongation and growth. The damp paper provides a constant supply of water.
2. **Controls for Hydrotropism:** Plant roots are positively hydrotropic, meaning they will grow towards water. If water were provided from one direction only (e.g., a puddle at the bottom), the roots would grow towards it, confounding the results of the gravity investigation. By using damp blotting paper, water is available evenly all around the root, so it does not provide a directional stimulus. This ensures the primary directional stimulus being tested is gravity.
Common mistakes
✗ Choosing "to prevent mould" - dampness encourages mould.
✗ Choosing "to prevent photosynthesis" - roots don't photosynthesise.
✗ Only selecting one correct answer.
Practice the full AQA GCSE Biology Higher Tier Paper 2
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