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

How does transpiration benefit plants?

1. It reduces water supply for photosynthesis

2. It increases temperature within the leaf

3. It helps support the plant and prevents wilting

4. It prevents gas exchange

The correct answer is: It helps support the plant and prevents wilting

Transpiration is the process by which water evaporates from the surfaces of leaves, specifically through small openings called stomata. This loss of water is crucial for a couple of significant reasons. One key benefit of transpiration is that it helps to maintain a flow of water from the roots through the plant. As water is lost from the leaves, it creates a negative pressure that pulls more water and nutrients upward from the roots. This movement is vital for transporting essential minerals and maintaining cell turgor pressure, which supports the plant’s structure and prevents wilting. If a plant cannot maintain turgor pressure due to insufficient water, it will begin to droop and can suffer damage. In context, the other choices provided do not accurately reflect the beneficial roles of transpiration. For instance, while it may seem that reducing water supply could affect photosynthesis negatively, transpiration actually facilitates nutrient and water uptake essential for photosynthesis to occur effectively. Similarly, transpiration does not inherently increase the temperature of the leaf, nor does it prevent gas exchange; in fact, it allows the exchange of gases like oxygen and carbon dioxide to take place through the stomata. Thus, the correct answer emphasizes the crucial role of transpiration in maintaining plant health and structure.