Xylem & the Transport of Water
The role of xylem
- Xylem cells form tubes that carry water and dissolved mineral salts in plants
- Water is transported from the roots, through the stem and into the leaves
- Here it is either used in photosynthesis or lost in transpiration
- Xylem vessels are adapted to allow water to move easily from the roots to the leaves, e.g.
- They are dead cells, meaning that they are hollow and water can flow through them easily
- They have no end walls to slow the flow of water
The role of transpiration
- Transpiration can be defined as
The loss of water vapour by evaporation from the leaves of plants
- Water evaporates from the surface of cells that line the air spaces inside leaves before exiting by diffusion
- Water diffuses out via the stomata
- More water is drawn up the xylem to replace the water that is lost in transpiration, ensuring a continuous stream of water inside the xylem
- This upward movement of water is known as the transpiration stream
- This supplies water to leaf cells for photosynthesis, as well as bringing dissolved minerals from the soil
Transpiration diagram
Water travels from the roots to the rest of the plant in the xylem before it is lost at the leaves by transpiration
