A Level Biology Practice Exam

What role does water play during transpiration?

1. It acts as a medium for nutrient transport

2. It provides structural support

3. It serves as a solvent for photosynthesis

4. It evaporates from leaves to cool the plant

The correct answer is: It evaporates from leaves to cool the plant

During transpiration, water is crucial because it evaporates from the surfaces of leaves, primarily through small openings called stomata. This process has several important roles. Firstly, the evaporation of water creates a negative pressure within the leaf, which helps to pull more water and nutrients from the roots through the xylem vessels. This upward movement of water not only aids in nutrient transport but also contributes to the cooling of the plant as the water loss helps to lower the leaf temperature. Additionally, while water indeed acts as a medium for nutrient transport and a solvent in other biochemical processes, during transpiration, its primary function is related to the evaporation process and cooling effect. Therefore, the evaporation of water from leaves to cool the plant is a vital role in maintaining optimal conditions for photosynthesis and overall plant health.