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

What do xylem tubes carry from the roots to the leaves?

1. Food substances

2. Oxygen

3. Water and minerals

4. Carbon dioxide

The correct answer is: Water and minerals

Xylem tubes are specialized structures in plants responsible for transporting water and dissolved minerals absorbed from the soil up to the leaves. This process is crucial for plant health as it not only provides the necessary hydration for photosynthesis but also supplies the minerals that contribute to growth and development. The water transported through xylem helps maintain turgor pressure within the plant cells, which is vital for structural support. Additionally, the movement of water creates a flow that assists in the upward transport of minerals from the roots to the rest of the plant, ensuring that the leaves receive everything they need to perform photosynthesis effectively. In contrast, food substances are transported through phloem tubes, oxygen is utilized in cellular respiration, and carbon dioxide enters the plant through stomata for use in photosynthesis. Thus, the role of xylem is specifically focused on the upward movement of water and minerals, making this choice the most accurate representation of its function.