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

Where is auxin primarily produced in a plant?

1. In the roots

2. In the leaves

3. In the tips

4. In the flowers

The correct answer is: In the tips

Auxin is primarily produced in the tips of the plant, specifically in the apical meristem, which is the region responsible for the elongation of the plant. This hormone is crucial for regulating growth and development. The production of auxin in the tips allows for the coordination of growth responses such as phototropism, where plants bend towards light, and gravitropism, where roots grow downward in response to gravity. The concentration of auxin is highest at the very top of the plant, and as it moves downward, it influences various growth patterns by promoting cell elongation. In contrast, while other parts of a plant like the leaves, roots, and flowers may also contain auxin, they play a relatively minor role in its production compared to the growing tips. This localized production ensures that the plant can effectively respond to environmental cues and optimize its growth.