Factors affecting transpiration

The rate of transpiration is affected by several factors. These include:

  • temperature
  • humidity
  • air movement
  • light intensity

The table below explains how factors increase the rate of transpiration:

FactorChange in factor that increases transpiration rateExplanation
TemperatureIncreaseIncreases molecular movement so that more water molecules evaporate from cell surfaces. The rate of diffusion of water molecules from the leaf is increased.
HumidityDecreaseReduces the concentration of water molecules outside the leaf. Diffusion of water from the leaf increases.
Air movementIncreaseRemoves water vapour from leaf surfaces. More water diffuses from the leaf.
Light intensityIncreaseIncreases the rate of photosynthesis. Stomata open so that water diffuses out of the leaf.

Plants living in different habitats have adaptations to resist extremes of these factors.


What conditions will decrease the rate of transpiration?

Decrease in temperature, increase in humidity, no or reduced air movement and low light intensities.