AQA GCSE · Question 03.6 · Homeostasis and Response
Give one stimulus a plant root responds to. Do not refer to light in your answer.
How to approach this question
Plant roots also show tropisms, but they respond to different stimuli than shoots, or respond in a different way. Think about what roots need to find in the soil and how they grow. The question asks for a stimulus, not the response itself.
Full Answer
Gravity / Water
Plant roots exhibit tropisms to help anchor the plant and absorb water and minerals.
1. **Gravity:** Roots show positive gravitropism (or geotropism), meaning they grow downwards in the direction of gravity. This helps anchor the plant securely in the soil.
2. **Water:** Roots show positive hydrotropism, meaning they grow towards areas of higher water concentration in the soil.
Common mistakes
✗ Answering "light". The question specifically says not to refer to light. (Roots are negatively phototropic).
✗ Giving the response (e.g., "grows down") instead of the stimulus (e.g., "gravity").
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