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

What is the response of shoots to gravity called?

1. Phototropism

2. Gravitropism

3. Hydrotropism

4. Thigmotropism

The correct answer is: Gravitropism

The response of shoots to gravity is known as gravitropism. This phenomenon refers specifically to how plants orient themselves in relation to gravitational forces. When a shoot grows upwards against gravity, it demonstrates positive gravitropism, while roots exhibit negative gravitropism by growing downwards toward the gravitational pull. In contrast, phototropism is the growth of plants in response to light, usually leading shoots to bend towards light sources. Hydrotropism pertains to how plant roots grow towards moisture or water. Lastly, thigmotropism describes how plants respond to touch or physical contact, such as the coiling of vines around supports. Understanding these various tropisms helps in realizing how plants adapt to their environment through different stimuli.