Part 4: Water and assimilate movement
7. Transpiration
Transpiration is the movement of water, against gravity, from the roots to the leaves of a plant, where any water that has not been used in photosynthesis evaporates through the stomata.
- Water enters the plant’s roots by osmosis.
- The water travels through the xylem tubes from higher water potential in the roots to lower water potential in the leaves.
- Water evaporates through the stomata in the leaves.
There are many factors that can affect transpiration:
| Temperature increases | Transpiration increases |
| Temperature decreases | Transpiration decreases |
| Water in soil increases | Transpiration increases |
| Water in soil decreases | Transpiration decreases |
| Light levels increase | Transpiration increases |
| Light levels decrease | Transpiration decreases |
| Wind speed increases | Transpiration increases |
| Wind speed decreases | Transpiration decreases |
| Humidity increases | Transpiration decreases |
| Humidity decreases | Transpiration increases |
Activity
Draw a diagram of transpiration in your notebook, showing water entering a plant through its roots, travelling up through the stem and exiting the plant by evaporating through the stomata in the leaf surfaces.