A Level Biology Practice Exam

What do xylem vessels primarily do?

1. Transport nutrients down the plant

2. Store excess water for the plant

3. Carry water up the plant

4. Facilitate gas exchange in leaves

The correct answer is: Carry water up the plant

Xylem vessels primarily function to carry water and dissolved minerals from the roots up through the plant to the leaves and other parts. This upward movement is crucial for various processes, including photosynthesis, where water is utilized. The structure of xylem vessels, which are made up of elongated cells that form sturdy tubes, is specifically designed to withstand negative pressure that is created during water transport due to transpiration in the leaves. In addition to transporting water, the xylem also supports the plant structurally, but its main role is the movement of water. This distinguishes it from other plant structures that might be responsible for storing water, transporting nutrients, or facilitating gas exchange. Understanding the role of xylem is essential for grasping how plant systems function and maintain homeostasis in relation to water and nutrient availability.