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

What role do stomata play in the process of transpiration?

1. They store water

2. They facilitate gas exchange

3. They close to minimize water loss

4. They transport nutrients

The correct answer is: They facilitate gas exchange

Stomata are tiny openings located primarily on the surfaces of leaves, and they play a crucial role in the process of transpiration. They facilitate gas exchange by allowing water vapor to exit the plant while also enabling carbon dioxide to enter for photosynthesis. During the day, when photosynthesis is actively occurring, stomata typically open to promote both gas exchange and the release of water vapor, which is part of the transpiration process. While stomata certainly help control water loss by facilitating this movement, their primary function directly related to transpiration is the exchange of gases. The opening and closing of stomata are also influenced by environmental conditions to help balance water loss and gas exchange. Thus, their function in facilitating gas exchange is fundamental to understanding how transpiration works within the overall physiology of plants.