- Transpiration refers to the loss of water vapour from a plant to its environment by diffusion
- The steeper the water potential (Ψp) gradient is, the greater the rate of transpiration
- Environmental factors that can cause a change in the water potential gradient are:
- Humidity (a measure of the concentration of water vapour in the air)
- Air movement / wind
- Light intensity
- Water availability
When relating the environmental factor to the effect on the rate of transpiration remember to compare the water potential gradient of the air spaces surrounding the mesophyll cells to the external air surrounding the stomata.