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

How does auxin affect leaf retention in plants?

1. By promoting leaf growth

2. By inhibiting leaf shredding

3. By accelerating leaf aging

4. By increasing leaf size

The correct answer is: By inhibiting leaf shredding

Auxin is a plant hormone that plays a critical role in various growth processes, including leaf development and retention. In terms of leaf retention, auxin works primarily by inhibiting the processes that lead to leaf abscission, or shredding. This means that auxin helps to keep leaves attached to the plant, promoting their longevity and overall health. When auxin levels are sufficiently high in a plant, it signals the cells in the leaf to remain active and resist the natural aging processes. As a result, leaves remain on the plant for a longer period, allowing for more efficient photosynthesis and nutrient absorption. The stabilization of leaf attachment is vital for the plant's growth and development since healthy leaves contribute significantly to the plant's ability to produce energy and support its metabolism. Promoting leaf growth and increasing leaf size, while important functions of auxin, do not specifically relate to the mechanism by which leaves are retained on the plant. Accelerating leaf aging would be contrary to the role of auxin in maintaining leaf viability and health. Thus, the impact of auxin on inhibiting leaf shredding directly correlates with increased retention of leaves on the plant.