A Level Biology Practice Exam

Which statement best describes the role of water through adhesion in plants?

1. It helps in nutrient absorption from soil

2. It facilitates the transport of minerals in the xylem

3. It assists in cooling plant tissues during photosynthesis

4. It enables the transport of water against gravity

The correct answer is: It enables the transport of water against gravity

The role of water through adhesion in plants is best described in the context of its ability to enable the transport of water against gravity. Adhesion refers to the attraction between water molecules and other substances, such as the walls of the xylem vessels. This property allows water to adhere to the xylem's inner surfaces, helping to counteract the force of gravity as water moves upward from the roots to the leaves. This mechanism is crucial for maintaining water transport in plants, particularly in taller species where gravity poses a significant challenge. The combination of cohesion (water molecules sticking to each other) and adhesion allows for capillary action, which is essential in drawing water upward through the plant's vascular system. In contrast, while water's role in nutrient absorption, the transport of minerals, and cooling plant tissues during photosynthesis are also important, they do not primarily involve the adhesive properties of water in the context of overcoming gravity. Therefore, the statement that best captures the specific role of water through adhesion in plants is that it enables the transport of water against gravity.