OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What happens when a root is exposed to light?

1. The root grows taller

2. The root bends upwards

3. The root stops growing

4. The root bends downwards

The correct answer is: The root bends downwards

When a root is exposed to light, it typically bends downwards. This phenomenon is known as phototropism, but in roots, it is generally overshadowed by geotropism, which is the directional growth in response to gravity. Roots are negatively phototropic, meaning they tend to grow away from light sources. This adaptation helps protect the root systems from potential damage caused by light and maintains their growth in the soil where moisture and nutrients are more readily available. In contrast to what might be expected with other types of plant organs, such as stems that grow towards the light, roots prefer to anchor deeper into the ground, ensuring stability and access to necessary resources. Therefore, the correct answer reflects the natural behavior of roots in response to light exposure, promoting their downward growth.