Water in the XYLEM -
The xylem is composed of dead cells that join together to form long, narrow, hollow tubes that are lined with lignin.
In plants, the majority of water is transported through hollow, thick-walled tubes called xylem vessels. Water is pulled through these xylem vessels due to the force created by evaporation of water from the plant's leaves. This process is TRANSPIRATION.
Water is able to move across the cells of a leaf as:
- Mesophyll cells lose water to the surrounding air spaces
- Those cells then take water from the neighbouring cells via osmosis
- The water potential of neighbouring cells is lowered
- In turn they then gain water via osmosis from other neighbouring cells
This develops a water potential gradient, pulling water from the xylem, across the mesophyll cells and into the atmosphere.
Water is able to move up the xylem (from roots to stem) due to COHESION TENSION THEORY.
- Water evaporated due to transpiration
- Due to air spaces being left empty beneath the stomata, COHESION pulls more water up
- H bonds form between water molecules
- This creates ADHESION, molecules stick to the walls of the xylem
- A continuous pathway of water across mesophyll cells form, resulting in…