Rate of transpiration

Two houseplants side by side. The one on the right is drooping and wilted.
Plants wilt and may die if they lose too much water

If the rate of transpiration increases, the rate of absorption of water by the root increases too. Factors that affect the rate of transpiration also affect water uptake by the plant. If water is scarce, or the roots are damaged, a plant may wilt.

Factors affecting rate

The rate of transpiration is affected by several factors, including:

  • temperature
  • humidity
  • wind speed
  • light intensity

This table shows the effects on the rate of transpiration when certain factors are increased.

TemperatureIncreasedEvaporation and diffusion are faster at higher temperatures
HumidityDecreasedDiffusion of water vapour out of the leaf slows down if the leaf is already surrounded by moist air
Wind speedIncreasedMoving air removes water vapour, increasing the rate of diffusion of water vapour from the leaf
Light intensityIncreasedThe stomata open wider to allow more carbon dioxide into the leaf for photosynthesis