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.