8.1 Xylem and phloem

Apuntes

• Subtopic: Plant Transport Systems All organisms need to obtain substances from their environment. For plants, these substances include carbon dioxide and water for photosynthesis, as well as mineral ions absorbed from the ground. Plants have branching shapes, which provide them with a large surface area relative to their volume. This structure ensures that most cells are close to the surface. As discussed in Chapter 6, leaves are adapted to ensure that no cell is far from the air, allowing carbon dioxide to diffuse in through the stomata and air spaces, easily reaching the photosynthesizing mesophyll cells. Water, however, comes from further away. Plants absorb water through their roots, and this water must be transported up to the leaves. The transport system responsible for this is made up of a tissue called xylem. Mineral ions are also transported in xylem. Additionally, plants have a second transport system composed of a tissue called phloem. Phloem transports sucrose and amino acids from the leaves, where they are made, to other parts of the plant such as its roots and flowers. • Subtopic: Vascular Bundles Xylem vessels and phloem tubes are usually found close together, ...