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

Which adaptation helps plants reduce water loss from their leaves?

1. Thicker leaves

2. A waxy cuticle

3. A greater number of stomata

4. Longer roots

The correct answer is: A waxy cuticle

The correct answer is the waxy cuticle. Plants have a waxy cuticle, which is a thin layer of water-repellent material that covers the epidermis of their leaves and stems. This cuticle plays a crucial role in reducing water loss through transpiration, which is the process where water evaporates from plant surfaces. By limiting the amount of water that can escape, the cuticle helps the plant retain moisture, especially in dry environments. Thicker leaves may help in some instances by providing additional storage for water or reflecting sunlight, but they do not directly address the evaporation concern like a waxy cuticle. A greater number of stomata, while important for gas exchange, could actually increase water loss if they are open too often. Longer roots enable plants to access deeper water sources, but they do not reduce water loss from the leaves themselves. Therefore, the waxy cuticle is the most effective adaptation for minimizing water loss.