BioNinja

Transpiration is the loss of water vapour from plants (predominantly from the leaves as a consequence of gas exchange)

• Light energy converts the water within the leaves into vapour, which then evaporates and diffuses from the leaf via the stomata
  

• New water is absorbed from the soil by the roots, creating a difference in pressure between the leaves (low) and roots (high)
  

• Water will flow – via the xylem – along the pressure gradient to replace the water lost from the leaves (transpiration stream)
  

The rate of transpiration by a terrestrial plant can be affected by a number of abiotic factors, including:

• Sunlight – Light stimulates the opening of stomata, as gas exchange is required for photosynthesis to occur

• Temperature – High temperatures increase the vaporisation of water, leading to greater diffusion from the leaf

• Wind – The flow of air functions to remove the water vapour surrounding the leaf, increasing diffusion rates  

• Humidity – A higher concentration of water vapour in the air will decrease the rate of diffusion from the leaf

Factors Affecting Transpiration

Sunlight

Temperature

Wind

Humidity